The most important key concepts of this chapter to me is the asexual vs sexual reproduction, how it works, and how one is more advantageous that the other. Also, the parts of the flower is important as well. I think knowing what each part of the flower is important and know their function. But since we’ve taken that lab practical, I’m sure we got most of those down. Knowing the photoperiodism definitions and making experiments out of them would be helpful as well. Knowing how pollination and fertilization happens and knowing the difference between selfing and outcrossing is key. And finally, knowing how the seed disperses, how seed dormancy works, and how it germinates is important. I feel that ABA will be an important concept too and how it works. Enjoy these notes and add on if you like!
Asexual vs Sexual Reproduction
– Sexual reproduction occurs in most plants. It is based on meiosis and fertilization which results in gametes that are unlike each other, the sperm and egg contain the DNA but the female and male parent contribute different amounts which results in variation.
– The life cycle that is characterized with land plants is that there are two forms, one diploid and one haploid. The diploid associates with a sporophyte while the haploid associates with a gametophyte. This is the alternation of generations. Once this occurs, meiosis does not lead directly to the formation of gametes but leads to the production of spores. Sporophytes produce spores by meiosis and gametophytes produce gametes by mitosis.
– Two examples show how the life cycles within land plants can be varied. One is the life cycle of a liverwort which the sporophyte is depended on the gametophyte for nutrition while the other is the life cycle of an angiosperm which the male and female gametophytes are microscopic and are completely dependent on the sporophyte for nutrition.
– Asexual reproduction occurs in plants as well. This is when fertilization is not involved and results in the production of clones: genetically identical to the parent plant.
– There are also variations of asexually reproducing such as in dandelions, their mature seeds can form without fertilization occurring.
– Key characteristic to asexual reproduction is efficiency. But, also has downside. Disease can infect the plant and will probably succeed in infecting it’s clone. No variation.
Flowering
– Flowering occurs when an apical meristem stops making energy stems and leaves and begins to produce the stems and leaves that make up flowers.
– Photoperiodism is a big part in flowering.
-Long-day plants: days are longest and nights are shorts, (radishes, spinach, corn)
– Short-day plants: days are shorter (mums, asters)
– Day-neutral plants: flowers without regard to photoperiod (weeds, cucumbers, tomatoes)
– Plants sense changes in day length through phytochrome. It is tied with the molecular mechanisms of timekeeping in plants.
– General structure of a flower includes: sepals, petals, stamens and anthers.
– Sepals make up outermost layer of flower. They enclose the flower bud as it develops and grows, protects the young buds from insects or diseases. Entire group of them is called calyx.
– Petals have variation in size, shape, and color. Color usually correlates with the visual abilities of animals and advertise the flower to bees, hummingbirds, flies. Entire group of petals is a corolla.
– Stamens produce pollen. Consists of the stalk which is theta filament and the pollen-producing organs at the top which are the anthers. Function of the filament is to hold stamen in place where wind, insects, can make contact with the pollen grains.
– Carpels produce the female gametophytes. They are produced in structures called ovules. Consists of the stigma which receives the pollen, the style which is the stalk, and the ovary which is the base of the carpel.
– Some flowers are monoecious which contains both stamens and carpels while some are dioecious meaning the flower contains either carpel or stamen, not both.
Pollination and Fertilization
– Pollination is the transfer of pollen grains from an anther to a stigma while fertilization is when the egg and sperm actually unite to form a diploid zygote.
– Pollen can fall on the stigma of the same individual or the stigma of a different individual.
– Selfing/ self-fertilization occurs when the sperm and an egg from the same individual combine to produce an offspring. Primary advantage is that successful pollination is assured. Doesn’t depend on other agents. Primary disadvantage is that there is less variation.
– Outcross/cross-pollination is when a sperm and egg from different individuals combine to form an offspring. Primary advantage is that it has genetically diverse offspring and can fight off diseases successfully. Disadvantage is that it is risks in terms of chances that pollination will occur.
– Cross-pollination can happen in different ways: pollen can be carried from flower to flower by wind/water or by insects.
– Animal pollination is usually an example of mutualism. They both benefit.
– Wind-pollinated species invest in making large number of pollen grains while animal-pollinated species make fewer pollen grains but attract and reward animals.
– Bumble bee would prefer a large flower that smells sweet because it supports the mass of the bee while a file would attract to small flowers that smell skunky for their benefit.
– Fertilization steps:
1. Pollen grain germinates on the stigma. Pollen tube begins growing down style.
2. Tube-cell nucleus moves into pollen tube. Cell nucleus devised by mitosis to form 2 sperm in pollen tube.
3. Pollen tube completes growth, discharges the 2 sperm into a cell near egg.
4. One sperm unites with egg to form zygote. The other form endosperm (“inside-seed” tissue).
The Seed
– When seed matures, embryo and endosperm develop inside ovule and become surrounded by covering called seed coat.
– Embryogenesis is the process by which a single-celled zygote becomes a multicellular embryo.
– Embryogenesis process:
1. Zygote divides into 2 daughter cells
2. 2 daughter cells divide into a cell mass and basal cell pule suspensor
3. cell mass differentiates into progenitors of the 2 adult tissues.
4. 3 tissues mature (cotyledons or seed leaves, hypocotyl (embryonic) stem, radicle or embryonic root). Once this happens, the seed dries and it stops growing.
– Drying occurs in seeds.
-How do proteins and plasma membranes survive during dry process? The answer involves sugar. As water leaves the seed during drying, sugars replace it. If drying is extreme, the sugars form a liquid that is glass-like which maintains the integrity of the plasma membranes and proteins in seeds.
– Fruits come in 3 types: simple fruits ( derived from single flower that contains a single carpel), aggregate fruits( derived from single flower that contains many separate carpels), and multiple fruits (derived form many flowers and thus many carpels).
– Fruits protect seeds from physic damage and seed predators and aid in seed dispersal.
– Seed dispersal through propulsion and animals
– Seeds may not germinate for a long time known as dormancy. ABA is responsible for this, prevents germination.
-Dormancy is broken if the seed coats are scarified.
– Seed germination occurs and first step is water intake. 2nd is a period without water. 3rd is water uptake occurs again as growth begins.
Hello,
I had Ch6 and the readings we had over the past four weeks only included 6.3 and 6.4, so that is what my notes will cover.
By relying on what was went over in class, the main ideas that would be helpful to study, for me anyway, would be, in no particular order 1) going from high to low, 2) comparing/contrasting of osmosis and diffusion, and 3) passive & active transport proteins. I too, felt these topics to be material that I should study a bit more. When I think of the movement from high to low I tend to over think things and confuse concentration of solute and concentration of water. But by pondering osmosis and diffusion I can think these concepts through better. Before I discuss anything else I want to say that it’s much easier to think of osmosis in terms of water potential than solute concentration. The book tends to think of the flow of water relative to the inside of the cell’s solute concentration, but I like water potential better. For me personally, solute concentration is inversely related to water potential. For example, high solute concentration (of outside) = low water potential. I know that diffusion is the movement of solutes so that equilibrium in concentrations is equal on both sides. Therefore for osmosis, what’s being compared is the concentration of water on each side, which is also equivalent to the comparison of water potentials. With, for example, the outside of the cell containing more solute than the inside and the solute not being able to diffuse inward, this environment is called hypertonic, because it contains more solute. Therefore this environment has a low water potential, as the concentration is so high here. And because the rule is that water will go from high water potential areas to low water potential areas, the water will flow outward, causing the cell membrane and vesicle to shrink. By thinking one idea through I was about to draw in another idea and view these ideas as one whole concept, allowing me a well-understood general viewpoint.
I also think some other concepts would be helpful to review. In this section the Na+/K+ pump was mentioned step by step, so looking back to the diagram on p98-99 may be helpful. By the way, this example portrays active transport because a phosphate binds to the membrane protein, which symbolizes the use of energy. The binding of a phosphate from ATP will cause the pump to have a conformational change, spewing out the previously attracted Na+ ions, allowing for the acceptance of K+ ions. The phosphate leaves, causing another conformational change that spews out the K+ ions, resulting in the original protein state that previously accepted Na+ ions. I mentioned passive transport and active transport up above, but haven’t said anything really about it. Just a reminder: active transport requires an energy (one phosphate) source because molecules/ions are being transported against the electrochemical gradient. And passive transport does not require energy to transport molecules/ions because they aren’t being moved against the electrochemical gradient (because of increased entropy).
I’m anticipating questions that compare osmosis & diffusion, as well as comparing active & passive transport, in addition to the proteins and molecules they utilize, and maybe a reference to the Na+/K+ pump. I think I can make sense of pumps and diffusion, but may be getting mixed up with the types of proteins used in facilitated diffusion (especially transporters and cotransporters).
6.3: Why Molecules Move across Lipid Bilayers: Diffusion and Osmosis
Diffusion
•Movement from areas of high solute concentration to areas of low solute concentration
•Spontaneous process when along a concentration gradient, b/c entropy increase
•Concentration gradient→formed by a difference in solute concentrations (net movement)
•Equilibrium = even distribution of solute concentrations on both sides of semipermeable membrane
-Molecule/ion movement rate is at continuous, even rate
Osmosis
•Movement along concentration gradient (from high water concentration to low water concentration)
•Osmosis→ the movement of water across a semipermeable membrane
•Water moves from high water potential area to low water potential area
-Allows for dilution of higher concentration and equalizes concentrations
•Hypertonic→In comparison to inside, outside of cell contains higher concentration of solutes; water moves out of cell to dilute outside, causing cell shrinkage
•Hypotonic→In comparison to inside, outside of cell contains lower concentration of solutes; water moves into cell to dilute inside, causing cell rupture
•Isotonic→Outside solute concentration same as inside solute concentration; no change to cell
Membrane proteins
6.4: Membrane Proteins
Membrane proteins
•Allow the passage of ions and molecules those usually are unable to pass through the semipermeable membrane of the cell
-Due to charge or size
•Transport proteins allow permeability of membrane
•Allow environments outside cells to be quite different from inside environments
Passive transport
•Is powered by diffusion along an electrochemical gradient
•Ion Channels→Allow for ions to pass through membranes on their own
-From high to low concentration (diffusion); from different to similar charge
-Movement of ions influenced by electrochemical gradient
•Channel proteins
-Selective; carefully monitored
-Composed of certain structure; allows admission of certain kind of ion or molecule
-Ex: Gated Channel→open/close in response to binding of particular molecule, or to change in the electrical charge on outside of membrane
•Facilitated diffusion→passive transport of material that doesn’t readily cross the membrane
Active transport
•Bring in molecules/ions against electrochemical gradient
•Requires energy
-Stems from one phosphate group, from an ATP
•Goes against electrochemical gradient
•Pumps
-Change of shape allows ion/molecule movement against electrochemical gradient
-Set up electrochemical gradients, collecting/throwing out of certain chemicals
•Cotransport
-Gradient set up by pump; gradient becomes source of energy to allow movement of different molecule against the gradient
Hey everyone!
In chapter 37 we learned about Water and sugar transport in plants and the various mechanisms of water movement. The main things to take away from this chapter was the idea of water and solute potential and the various hypotheses of water and sugar transport . For example, an important concept would be that water moves from areas of high water potential to areas of low water potential. This is driven by 2 things, solute potential and pressure potential. Both of which you will need to have a good idea of, especially solute potential. This is connected to the idea of osmosis , which has to do with water movement through a semi permeable membrane. Know vocab terms such as isotonic and hypotonic. We also read about different types of soils, such as dry and salty soil. Know how these effect solute potential and how plants are able to adapt to these changes in soil. For example an oleander plant has several cell layers of epidermis to lower water loss which is why it thrives in dry environments. Review the cohesion-tension theory and the Pressure flow hypothesis of sugar transport.
Here is a brief outline:
• Transpiration: loss of water via evaporation from aerial parts of a plant
○ When stomata are open
○ Air surrounding the leaves are drier than air inside leaves
• Water potential: potential energy that water has in a particular environment
○ Differences in water potential determine direction the water moves
○ Moves from areas of high water potential to areas of water potential
• Isotonic: solute concentration in cell and outside cell are equal
• Osmosis: water movement in response to solute concentration through semi permeable membranes
○ Solute potential is seen in terms of solute concentration relative to water
○ High concentration in water=low solute concentration
○ Water moves from regions of low solute concentration to regions of high solute concentration
• Water potential in soils, plants and atmosphere
○ In dry soil, water does not float around freely
○ Water clings to soil particles thus creating negative pressure tjat lowers pressure potential of water
○ Species adapt to this by lowering the solute potential of root cells
○ Species in dry areas cope by adapting to dry areas
§ They are able to tolerate low solute potentials
§ Usually when soils dry, water potential drops but if solute potential goes down as well , it can maintain a water potential gradient that continues to bring water into plants
○ Limiting Water loss
§ Have adaptations that limit water loss
§ Help slow transpiration and limit water loss
§ For example oleander leaves have thick cuticle that covers the upper surface
§ Epidermis can be several layers deep
§ Stomata can be located in undersides of a leave, in deep pits of the epidermis, have hair like stuff on epidermal cells to protect from atmosphere
□ Hypothesis is that they slow loss of water vapor
§ Long thin leaves, smaller surface area
• Casparian Strip and Suberin
○ The Casparian strip is by the endodermis, endodermal cells are tightly packed and secrete a waxy substance called suberin, this waxy layer is called the Casparian strip
○ Purpose is to block water from moving through walls of endodermal cells
○ Important because it is the means that for water and solutes to reach vascular tissue , they have to move into the cytoplasm of an endodermal cell, the cells act as filter
• Root Pressure
○ Movement of water and ions result from this
○ One of the three hypothesized mechanisms for moving water up xylem
○ Stomata close at night, which results in minimization of water loss and slow movement of water into roots, roots still accumulate ions though
○ Move into xylem
○ Lowers water potential of xylem, below water potential of surrounding cells
○ Makes water move up into xylem from other root cells
○ Positive pressure generated, fluids build up in xylem
○ Guttation: occurs in low growing plants, water can move to force water droplets out of leaves, for example when we see dew on leaves in the morning
• Cohesion- Tension Theory
○ Leading hypothesis to explain long distance water movement
○ Check out the diagram in the book: Figure 37.10
○ Water is pulled from tops of trees along water potential gradient, via forces generated by transpiration
• Pressure Flow hypothesis
○ Events at source tissue and sink tissues create large pressure potential
○ Based on movement along water potential gradient created by changes in pressure potential
○ Check out Figure 37.17 for understanding on pressure potential
• Phloem loading and Unloading
○ Loading
§ to establish high pressure potential in sieve-tube members near source cells, a whole lot of sugar has to be transported into phloem sap to raise solute concentration
§ Pg. 731
○ Unloading
§ Sucrose is unloaded along concentration gradient into an important sink: young, growing leaves
§ Pg. 734
○ Phloem sap moves from areas of high water potential to areas of low water potential
• CHECK YOUR UNDERSTANDING
○ Pg. 734
Photosynthesis Harnesses Sunlight to Make Carbohydrates
-Light Dependent Reaction vs. Light Independent Reaction
+Calvin Cycle is light independent
+The two reactions are connected by NADP+ which carries electrons from the light dependent reaction to the independent ones.
How Does Chlorophyll Capture Light Energy?
-Chlorophyll – Absorbs red and blue light
-Carotenoids – Absorb blue and green light
-Flavonoids – Absorb ultraviolet light and protect the plant
The Discovery of Photosystem II and I
-Photosystem II – Produces a proton gradient that drives the synthesis of ATP
1.Chlorophyll is hit by a photon
2.Pheophytin accepts the electrons from the chlorophyll
3.These electrons are passed onto the electron transport chain in the thylakoid membrane.
4.The electron transport chain sets up a proton gradient that drives ATP synthase
5.Photosystem II obtains electrons by oxidizing water
-Photosystem I – Produces NADPH
How is Carbon Dioxide Reduced to Produce Glucose?
-Calvin Cycle – Located in the stroma of chloroplasts
+Fixation Phase
+Fixes carbon to produce 2 molecules of 3-phosphoglycerate
-Reduction Phase
+3-phosphoglycerate is reduced by NADPH to form glyceraldehyde-3-phosphate(G3P) which can then be made into fructose and glucose
-Regeneration Phase
+The rest of the G3P keeps going through the cycle and acts as the substrate
-Rubisco – CO2 fixing enzyme
+Extremely inefficient enzyme that is very slow and can also catalyze O2 to RuBP which makes its CO2 fixing properties even more inefficient
The most important point of this chapter is to understand how photosynthesis actually works. Be able to answer questions such as:
What drives photosynthesis?
What are the products of photosynthesis?
What is the difference between photosystem I and II?
Be able to explain to someone else how photosynthesis works
Useful diagrams in the book are 10.14 on page 183, and 10.18 on page 186.
Helpful videos for understanding photosynthesis: http://youtu.be/-rsYk4eCKnA
Also, some additional information on C4 and CAM plants which we only talked a little about in class.
Photorespiration is when O2 instead of CO2 is fixed to the RuBP which is a waste process for a plant.
In C4 plants the calvin cycle (aka light independent reaction) happens in bundle sheath cells which are deeper in the cell and not in the mesophyll. PEP acts as a ferry which ferries CO2 from the mesophyll to the bundle sheath cells. In this way the plant is able to isolate CO2 away from O2 so no photorespiration will take place. I have a more detailed summary below but this is the basic idea.
C4 plants are able to use a different process involving PEP carboxylase which selects CO2 and leaves O2 and fixes it to a 3 carbon molecule called PEP to make a 4 carbon molecule. This 4 carbon molecule then moves into what is called bundle sheath cells which are further in the cell and away from O2 and is broken back down into CO2 and the 3 carbon molecule PEP again. PEP then goes back into the mesophyll and does its thing with another CO2 and now we have isolated CO2 in a bundle sheath cell with no O2 so no photorespiration will take place. This is my summary of the process if you couldn’t follow you can look at this video…
CAM plants are like desert cacti. As you can imagine the desert is hot and cacti want to retain their water during the day so they want their stomata closed. But if you have your stomata closed then you can get CO2 during the day (which is when photosynthesis happens) when you really need it. CAM plants do something interesting at night. They open their stomata during the night, when they wont lose a lot of water, and gather CO2. They turn this CO2 to a 4 carbon molecule and store it in a vacuole and during the day this gets turned back into CO2 which can be used for photosynthesis. This is how CAM plants get passed the fact that their stomata are closed during the day.
If you have any questions about CAM plants heres the link I used to help me
Chapter 39: Plant Sensory Systems, Signals, and Responses
Signal Transduction:
• Plant senses through signal transduction which means the receptor receives a signal and changes the form from external signal to intracellular signal.
• Two types of signal transduction:
– Phosphorylation cascades-when a receptor receives a signal, it changes its shape which causes addition of phosphate from ATP to receptor or inactive protein to activate and this process continues down the cell or changes to second messenger.
– Second messenger-it happens when producing intracellular signal result in hormone binding or release from the storage. Calcium ions are usually second messengers and they are stored in vacuole.
• Hormones are tiny molecules in tiny concentrations, but they have a big results.
Phototropism:
• We spend almost half the lecture period talking about phototropism, movement of plants toward light so I would expect something similar will be on the exam. So going over the experimental designs we came up during class is not a bad idea. Maybe try coming up with your own.
• Phototropism caused by a hormone called Auxin. When plant was exposed to light, it bend forward to the light and Auxin moves away from light. This causes proton pump to pump proton against the electrochemical gradient into the extracellular matrix allowing pH enzymes to loosen up its structure for growth (it called acid-growth hypothesis).
• Plants shows phototropic response only if blue wavelength is present, because blue light is important for photosynthesis. Only the tip of shoots respond to the blue light and distribution of Auxin happens.
Guard Cell Opening:
• Signal: Sunlight (particularly blue light)
• Proton Pump: Making the cell more negative
• K+ enters the cell through their channel along electrochemical gradient and H+ and Cl- enters the cell through cotransporter.
• Water rushes in following the solutes, because there is low potential of water in the cell.
• Guard cell opens
Guard Cell Closing:
• Cl- leaving/ ABA stops ATPase
• K+ leaving
• Water rushes out following the solutes
• Guard cell closes
Chapter 38: PLANT NUTRITION
What’s up everyone. Here’s a summarization of Ch 38, covering the important sections and concepts that our teacher covered. I broke it down so that it’s easier to understand.
This question got me when our professor asked it to us so I’m going to ask it again. When a growing plant gets bigger, where does its mass come from? Is it soil, water, air, or sun?
-If you answered soil, water, or air, you are incorrect. Please go over 4/4/13 PowerPoint again.
Nutrients
96% of plants weight comes from carbon, hydrogen, oxygen. So for their nutrients, plants need carbon dioxide (CO2) and water (H2O), but also need some a variety of essential nutrients to help growth What does it mean to be an essential nutrient? Basically, it’s required for growth, bodily functions, and reproduction.
• Macronutrients: need large amounts of N, P, K for synthesis of proteins, carbohydrates, etc. -Nitrogen, Phosphorus, Potassium are also known as limiting nutrients: limits plants growth.
• Micronutrients: need small amounts for growth (e.g. iron, magnesium)
Question: Are you able to design an experiment to tell whether nitrogen, or phosphorus is the limiting nutrient in the plant? Could we tell whether a plant is lacking nitrogen or phosphorus just by looking at the color of its leaves?
Nutrient Availability and Uptake
The elements that are needed for plant growth are found in soil as ions: anion = – , cation = + . Anions are readily available but washes off easily, while cations bind to soil particles and can be released by cation exchange. Cation exchange is when H+ protons bind to the soil particles while simultaneously other cation nutrients like Mg+ for example gets released in return.
Now let’s go further into how these nutrient ions pass through the root hairs using a proton gradient. In this gradient, proton pumps are created where H+ ions (protons) are pumped out of the cell in order to allow other positive ions to come in via channels. As for negative charged particles, a proton is pumped out in order for an anion to be transported in with a proton through a cotransporter (basically, a proton holds the hand of the opposite charge in order to come in).
Plants have many different ways of obtaining their nutrients
• Bacteria can colonize on the root nodules of plants and mutually exchange nutrients with nitrogen fixation. A bacterium gets protection and sugar while the plant receives ammonia.
• Carnivorous plants can trap and digest different insects and animals. They can survive low nitrogen atmospheres because they easily obtain nitrogen through their food.
• Parasitic plants can attach itself to the xylem of host plants and steal nutrients and water.
Terms on plant quiz covered on chapter 38
(V) Metallothioneins: proteins that attaches itself to metal ions to stop it from poisoning the plant.
(V) Leghemoglobin: a protein that binds to oxygen in order to prevent it from poisoning an enzyme that’s needed for nitrogen fixation.
What is nitrogen fixation? It’s when bacteria or archaea can absorb N2 and convert it to ammonia, nitrite, or nitrate.
(V) Hydroponics: growth of plants in liquid, without soil. The availability of nutrients can be accurately controlled.
Hey guys! Here are some bulleted points of things that Bryan has been stressing throughout the quarter as well as some experimental questions to ask yourself while studying these 🙂
Chapter 36 Form and Function
Plants have a root and shoot system
Root Systems: The below portion of a plant that anchors ad takes in water and nutrients from the soil such as nitrogen, phosphorus and potassium. They absorb selected nutrients from soil, conduct water and nutrients to shoots and stores nutrients for later.
• The importance of Surface Area/ Volume
o A plant is more efficient as an absorbance and synthesis machine when it has a large surface area compared to its volume.
This is why most roots are long skinny tubes
• Taproot System
o Most plants have a vertical taproot with lateral roots branching off of it.
o example of taproot system
• Phenotypic differences
o Plants will change their shape if presented with an obstacle. For example, a tree in a water logged area will keep its roots close to the surface in order to get more oxygen and a tree in a dry area will have deep roots.
o How would you test this with a transplant test?
o How would you test this with a dose experiment?
• Diversity has its advantages
o Biologist have found that natural selection favors structures that minimize competition.
o This is shown through Figure 36.4 where it shows different Prairie plants that would live together. Each has a very different set of roots demonstrating that they are each searching for resources in a different area so they aren’t competing together.
o Experiment! How would you test this theory?
A way I would do it would be to find several plants that share the same basic root shape and plant them in a confined area, wait a few months and see if any had died out or if they modified their shape in order to coexist.
• Special Roots
o Ivy have roots that allow them to cling to walls
o Prop roots help support corn and keep them up off the ground
o Mangroves have little sprigs of roots popping up out of the ground for gas exchange.
o Contractile roots pull the plant deeper underground as if to plant themselves, many bulbs do this.
• Fun Facts!
o A researcher grew a winter rye plant for four months and then measured the roots. He found that it had a combined length of 11,000 km
o Roots of trees are often wider than their canopies
o It is not unusual for root systems to make up 80% of the plant’s overall mass
Shoot system: A repeating series of nodes, internodes, leaves, and buds.
• Anatomy
o Stems-above ground structures
o Nodes, where leaves are attached (internodes-area between nodes)
o Leaf- photosynthetic organs
o Branch-structure off of shoot system
o Apical bud- top bud
o Maybe flowers- reproduction sites
• Diversity!
o Just like roots, shoot systems also vary in order best use their energy for growth and not competition.
o This can be done with varying branch angles and different internode lengths.
Ex. Some are short and bushy, some are tall and slender
o How would you test this?
Transplant idea: take a plant that has been growing as a short bushy plant and put it in an area that had a lot of taller plants choking out its light. Observe it’s growth
o Different phenotypes. Plants will alter their shape for their environment
Ex. Different elevations
o How would you test this?
Move plants from different elevations and see if their growing patterns change.
o Special shoot modifications
Stolons- like strawberries
Tubers- like potatoes
Thorn- like blackberries
Rhizomes- like canary grass
• Leaves
o Growth patterns
Alternate
Opposite
Whorled
o Different types of leaves
Simple
Compound
Complex
Needles
(one node per leaf)
o Questions
What are the advantages to these different shapes of leaves?
Hi guys, chapter 37 contains a lot cool stuff. I try to highlight the important parts from both lecture and book. Key terms and summary with some aid of catch-up questions.
Transpiration: the loss of water through the stomata
What is water potential?
Transpiration occurs when two conditions are met:
1). Stomata are open, usually during the day when photosynthesis is occurring.
2). The air in the environment is drier than the air inside the leaves.
Water moves up a plant because of differences in the potential energy of water. Plants replace water by moving water up the plant by a water-potential gradient, the overall movement of water when a series of water potentials differences are contrasted. Plants tend to gain water from the soil and lose it to the atmosphere.
1) Water potential is the potential energy that water has in a particular situation compared to the potential energy of pure water at atmospheric pressure at the same temperature.
2) There is a water-potential gradient between the roots and the leaves.
3) Q: Water moves from areas of ____ water potential to areas of ____ water potential.
A: high; low
What factors affect water potential?
If you are familiar with the idea hypotonic, hypertonic and isotonic, Osmosis is the process by which water moves across the semipermeable cell membrane.
Iso means inside equals outside, hypo means inside greater than outside, hyper is inside less than outside.
Solute potential is the tendency of water to move by osmosis, defined by its solute concentration relative to pure water. Page 718, figure 37.1, has a better visual illustration.
Q: What are the two main factors that affect water potential?
A: Solute concentration and physical pressure
How to calculate the water potential?
It is quite easy to calculate the water potential, its unit is megapascal. Generally, water moves from higher water potential to lower water potential. The pressure potential from turgor pressure is positive inside cells; it thus increases the water potential and increases the probability that water will move out of the cell. In most situations, the water potential of plant cells is lower than that of the surrounding solution, water moves into cells.
Turgor pressure: the pressure that is exerted on the inside of cell walls and that is caused by the movement of water into the cell
Ψ = ΨS + ΨP; S=solute; P=pressure (i.e. water moves up trees by moving down the gradient)
Q: Solute potentials are always _______.
A: negative (because they are measured relative to to the solute potential of pure water, which is zero)
When positive turgor pressure plus the cell’s negative solute potential equals zero, the system reaches equilibrium. At equilibrium there is no net movement of water in/out of the cell.
Q: What three major hypotheses have biologists suggested for how water can be transported in a plant?
A: Root pressure, capillary action, cohesion-tension
Water movement via root pressure, pressure potential that develops in roots, could drive water up against the force of gravity. It is generated after the stomata closed.
1. The endodermis (inner layer) is responsible for root pressure.
2. During the night, the root accumulates ions taken up by the epidermal cells.
3. These ions are transported to the xylem, decreasing its water potential.
4. Water flows into the xylem, creating positive pressure and pushing the water up the xylem toward the leaves.
5. transpiration is low at night, the water being pushed into the leaves escapes through small pressure valves, resulting in guttation. (Fig. 37.8)
Xylem: vascular tissue that carries water upward from the roots to every part of a plant.
Capillary action: could draw water up the cells of the xylem. Capillarity occurs in response to three forces: surface tension, adhesion, and cohesion.
Cohesion-tension: force generated in leaves, could pull water up from the roots through the xylem. It is an explanation for the movement of water up the stem xylem of tall plants; states that water is pulled up the xylem vessels by the cohesive force between the water molecules and the adhesion of the water molecules to the rigid vessel walls.
Water transport is powered by solar energy in this process.
This webpage illustrates phloem. Sink is the part that tissue where sugar exits the phloem. https://www.boundless.com/biology/water-and-solute-management-in-plants/sugar-transport-via-phloem/transport-from-sugar-sources-to-sinks/
Experiments on sugar-beet plants allowed researchers to track the movement of carbon atoms through plants to see the connection between sources and sinks.
Experiments showed there is a strong correspondence between the physical location of sources and sinks.
Pressure-flow hypothesis is that when nutrients are pumped into or out of the system, the change in concentration causes a movement of fluid in the same direction.
bulk flow: The movement of a fluid due to a difference in pressure between two locations (pressure gradient)
phloem loading: sucrose is moved by active transport from source cells through companion cells to sieve-tube members.
phloem unloading: companion cells move sucrose from the sieve-tube members into sink root cells by active transport, creating phloem sap with a low sugar concentration.
The net result of phloem loading and unloading is high turgor pressure near the source and low turgor pressure near the sink, which drives phloem sap from source to sink via bulk flow.
I was rushing through the chapter and slides we discussed in class. Welcome to help me adding more stuff that can help us better understand this interesting part in plant physiology.
Alright so I had experimental design as a topic and I’ll go through a few things trying to work it out and hopefully it’ll help you guys too. The main thing that Bryan stresses is variation when he gives you an experiment he doesn’t want to see 5 dose response experiments he maybe wants to see 2 dose response, as well as a control, rescue, take away that sort of thing.
Here is an experimental question I came up with…
You notice that corn seeds grown in light develop a long, thick, purple root (shut up I know what you’re thinking) with no branches while corn seeds grown in dark develop multiple thin roots with branches (yes this was from our experiment). What could be causing this to happen and what experiments would you do to find out?
So what do we have in our tool box to work with?
Control and negative control: Making sure that the seeds aren’t defective
Dose Response: Changing the amount that it gets to see if this has an influence
Take away: Taking something important away to determine if this specific thing is causing what you’re seeing.
Transplantation: transplanting an organ to see if this would cause the same effect.
Rescue: Giving the plant something vital it needs/ opposite of take away
Part 1: The first part would be to brainstorm what could be causing the issue. An obvious one is light but there is also heat (caused by light) or increased humidity caused by heat. These can all be translated into hypothesis that will help you in designing an experiment.
Part 2: The experiments…
Dose response: Again Bryan wants to see variation so we could do a couple experiments where we test corn in 6 hours of light and then again in 12 hours of light to see if this would cause the root to become purple and not spread out. This would be a dose response
Controls are easy you would just grow the corn in dark and light to make sure they will grow and your observation is reproducible
Take away: A good take away would be to grow the plant in light and then take this away about halfway through the experiment. This could show whether or not this change in variables would cause the root to begin to expand or not.
Another take away could be that you just take away other variables until you arrive at the last remaining one. You could take away the variable of humidity and keep them the same then you could take away the variable of heat by keeping this the same. This would allow you to see what exactly is causing the different root growth.
Rescue: A possible rescue for this would be to grow it in dark and then transfer it to light (technically you are rescuing the plant) to see if the root then changes into a purple root. This is the opposite of the take away experiment that we saw earlier
Transplantation: This one is easy you could transplant a purple root from a corn seed grown in the light to a corn seed grown in the dark and see if the root will continue to be a purple root or if the root begins to spread out and vice versa.
Let me know if you guys come up with any other experiments that you can think of or if you thought that I was totally wrong on one of the experiments.
Yipes! I wrote this all up yesterday and almost forgot to post it!
Core concepts in physiology
I’m going to try and give an example of something we have covered and connect it to the following core concepts.
1. Homeostasis
What jumped to mind immediately for me was osmosis and electrochemical gradients. Homeostasis is the tendency of a cell to regulate its interior to match the conditions of its exterior; to create a balance (homeo – stable; stasis – static).
Imagine a cell with a high concentration of solute inside and relatively low concentration of solute outside (the solution is hypotonic). The high water potential on the outside presses water across the membrane into the cell until the relative concentration of the solute is equal on both sides; until it is stable.
2. Cell membranes
In class we discussed how plant cells move important ions across membranes. Because ions do not travel easily across semi-permeable membranes they require the help of a few different types of proteins: channel, pump, transport, and co-transport. Remember, while all of these proteins allow the movement of ions across a membrane, only the pump requires the input of energy in the form of ATP.
3. Cell-cell communications
If you haven’t had a looked at the video of the sensitive plant, do it. It’s way cool. It’s also a great example of signal transduction. When a cell (plant or animal) receives an external signal (from another cell or the environment) a receptor protein will change conformation. This protein then catalyzes a phosphorylation (ATP in, ADP out). From here one of two things can happen: either a phosphorylation cascade is triggered (a series of proteins are phosphorylated over and over) or a second messenger is released (a stored or produced compound; the book uses Ca+ as an example). Ultimately this set of reactions with either release a hormone to be passed along to another cell (and the process starts over) or some other mechanism is triggered. I’d love to know what exactly the sensitive plant is responding to (heat, friction, etc.)…
4. Interdependence
Connections, connections, connections. For plants, mycorrhizae are my favorite example. This is the symbiotic connection between certain fungal species and over 80% of all plants. These fungi are more efficient at breaking down amino acids in the soil and absorbing other forms of nitrogen than the plants themselves. In exchange for the nitrogen that the fungi collect, plants trade out some of their photosynthetic byproducts; sugars. In this way, the fungi need the plants for their sugar and the plants need the fungi for their nitrogen.
5. Flow down gradients
Osmosis. In order to reach a homeostatic equilibrium, cells will exchange water across cell membranes until the relative concentration of solutes on one side is equal to the other. Think about the eggs in our break out group (and how I was apparently tasting each solution…). If there were more of a solute on the outside of an egg (the solution was hypertonic) all the water in the egg would flow out to reach an equilibrium (it got all shrivelly). The water moved from high water potential to low water potential.
6. Structure/function
Rhizomes. The potatoes that we all eat are actually parts of the stem of the potato plant (not in fact its roots). These specialized stems are ideal for storing carbohydrates (starches in the case of potatoes) and are what makes them such dense sources of nutrients. This size and position of the potatoes’ rhizome is important for its survival during the off season. When winter rolls around and the potatoes stop photosynthesizing, it relies on the stored sugars in the rhizomes until spring arrives and it can begin synthesizing new sugars.
7. Phenotypic plasticity
Phototropism. Phenotypic plasticity is the ability of an organism to change its physical characteristics in response to an environmental change. In the case of phototropism, remember that plants tend to grow toward a light source. This is caused by the presence of the hormone auxin which elongates the cell on the side of the plant furthest from the light. Auxin triggers a proton pump that acidifies the cell wall and “loosens” the fibers that make it rigid. Osmotic pressure makes the cells with loose cell walls bulge and expand making one side of the stem larger than the other causing it to lean toward the light.
I loved your explanations and connections to the class!
I’d love to know what exactly the sensitive plant is responding to (heat, friction, etc.)…
When you said that, it made me smile. What a good test question.
I need to think about phototropism as an example of phenotypic plasticity. On one hand it is right on, yet something doesn’t sit quite right with me. I think it is the time scale of the changes. Phototropism can occur within an hour. To me, phenotypic plasticity takes longer usually. But I don’t know why I lean that way. Just and FYI. Thanks for making me think.
BBIO220 Physiology Blog! Whoo Hooo!
Ch. 40: Plant Reproduction Notes
Hey guys!
The most important key concepts of this chapter to me is the asexual vs sexual reproduction, how it works, and how one is more advantageous that the other. Also, the parts of the flower is important as well. I think knowing what each part of the flower is important and know their function. But since we’ve taken that lab practical, I’m sure we got most of those down. Knowing the photoperiodism definitions and making experiments out of them would be helpful as well. Knowing how pollination and fertilization happens and knowing the difference between selfing and outcrossing is key. And finally, knowing how the seed disperses, how seed dormancy works, and how it germinates is important. I feel that ABA will be an important concept too and how it works. Enjoy these notes and add on if you like!
Asexual vs Sexual Reproduction
– Sexual reproduction occurs in most plants. It is based on meiosis and fertilization which results in gametes that are unlike each other, the sperm and egg contain the DNA but the female and male parent contribute different amounts which results in variation.
– The life cycle that is characterized with land plants is that there are two forms, one diploid and one haploid. The diploid associates with a sporophyte while the haploid associates with a gametophyte. This is the alternation of generations. Once this occurs, meiosis does not lead directly to the formation of gametes but leads to the production of spores. Sporophytes produce spores by meiosis and gametophytes produce gametes by mitosis.
– Two examples show how the life cycles within land plants can be varied. One is the life cycle of a liverwort which the sporophyte is depended on the gametophyte for nutrition while the other is the life cycle of an angiosperm which the male and female gametophytes are microscopic and are completely dependent on the sporophyte for nutrition.
– Asexual reproduction occurs in plants as well. This is when fertilization is not involved and results in the production of clones: genetically identical to the parent plant.
– There are also variations of asexually reproducing such as in dandelions, their mature seeds can form without fertilization occurring.
– Key characteristic to asexual reproduction is efficiency. But, also has downside. Disease can infect the plant and will probably succeed in infecting it’s clone. No variation.
Flowering
– Flowering occurs when an apical meristem stops making energy stems and leaves and begins to produce the stems and leaves that make up flowers.
– Photoperiodism is a big part in flowering.
-Long-day plants: days are longest and nights are shorts, (radishes, spinach, corn)
– Short-day plants: days are shorter (mums, asters)
– Day-neutral plants: flowers without regard to photoperiod (weeds, cucumbers, tomatoes)
– Plants sense changes in day length through phytochrome. It is tied with the molecular mechanisms of timekeeping in plants.
– General structure of a flower includes: sepals, petals, stamens and anthers.
– Sepals make up outermost layer of flower. They enclose the flower bud as it develops and grows, protects the young buds from insects or diseases. Entire group of them is called calyx.
– Petals have variation in size, shape, and color. Color usually correlates with the visual abilities of animals and advertise the flower to bees, hummingbirds, flies. Entire group of petals is a corolla.
– Stamens produce pollen. Consists of the stalk which is theta filament and the pollen-producing organs at the top which are the anthers. Function of the filament is to hold stamen in place where wind, insects, can make contact with the pollen grains.
– Carpels produce the female gametophytes. They are produced in structures called ovules. Consists of the stigma which receives the pollen, the style which is the stalk, and the ovary which is the base of the carpel.
– Some flowers are monoecious which contains both stamens and carpels while some are dioecious meaning the flower contains either carpel or stamen, not both.
Pollination and Fertilization
– Pollination is the transfer of pollen grains from an anther to a stigma while fertilization is when the egg and sperm actually unite to form a diploid zygote.
– Pollen can fall on the stigma of the same individual or the stigma of a different individual.
– Selfing/ self-fertilization occurs when the sperm and an egg from the same individual combine to produce an offspring. Primary advantage is that successful pollination is assured. Doesn’t depend on other agents. Primary disadvantage is that there is less variation.
– Outcross/cross-pollination is when a sperm and egg from different individuals combine to form an offspring. Primary advantage is that it has genetically diverse offspring and can fight off diseases successfully. Disadvantage is that it is risks in terms of chances that pollination will occur.
– Cross-pollination can happen in different ways: pollen can be carried from flower to flower by wind/water or by insects.
– Animal pollination is usually an example of mutualism. They both benefit.
– Wind-pollinated species invest in making large number of pollen grains while animal-pollinated species make fewer pollen grains but attract and reward animals.
– Bumble bee would prefer a large flower that smells sweet because it supports the mass of the bee while a file would attract to small flowers that smell skunky for their benefit.
– Fertilization steps:
1. Pollen grain germinates on the stigma. Pollen tube begins growing down style.
2. Tube-cell nucleus moves into pollen tube. Cell nucleus devised by mitosis to form 2 sperm in pollen tube.
3. Pollen tube completes growth, discharges the 2 sperm into a cell near egg.
4. One sperm unites with egg to form zygote. The other form endosperm (“inside-seed” tissue).
The Seed
– When seed matures, embryo and endosperm develop inside ovule and become surrounded by covering called seed coat.
– Embryogenesis is the process by which a single-celled zygote becomes a multicellular embryo.
– Embryogenesis process:
1. Zygote divides into 2 daughter cells
2. 2 daughter cells divide into a cell mass and basal cell pule suspensor
3. cell mass differentiates into progenitors of the 2 adult tissues.
4. 3 tissues mature (cotyledons or seed leaves, hypocotyl (embryonic) stem, radicle or embryonic root). Once this happens, the seed dries and it stops growing.
– Drying occurs in seeds.
-How do proteins and plasma membranes survive during dry process? The answer involves sugar. As water leaves the seed during drying, sugars replace it. If drying is extreme, the sugars form a liquid that is glass-like which maintains the integrity of the plasma membranes and proteins in seeds.
– Fruits come in 3 types: simple fruits ( derived from single flower that contains a single carpel), aggregate fruits( derived from single flower that contains many separate carpels), and multiple fruits (derived form many flowers and thus many carpels).
– Fruits protect seeds from physic damage and seed predators and aid in seed dispersal.
– Seed dispersal through propulsion and animals
– Seeds may not germinate for a long time known as dormancy. ABA is responsible for this, prevents germination.
-Dormancy is broken if the seed coats are scarified.
– Seed germination occurs and first step is water intake. 2nd is a period without water. 3rd is water uptake occurs again as growth begins.
WOW!!! We really learned a lot…….
Hello,
I had Ch6 and the readings we had over the past four weeks only included 6.3 and 6.4, so that is what my notes will cover.
By relying on what was went over in class, the main ideas that would be helpful to study, for me anyway, would be, in no particular order 1) going from high to low, 2) comparing/contrasting of osmosis and diffusion, and 3) passive & active transport proteins. I too, felt these topics to be material that I should study a bit more. When I think of the movement from high to low I tend to over think things and confuse concentration of solute and concentration of water. But by pondering osmosis and diffusion I can think these concepts through better. Before I discuss anything else I want to say that it’s much easier to think of osmosis in terms of water potential than solute concentration. The book tends to think of the flow of water relative to the inside of the cell’s solute concentration, but I like water potential better. For me personally, solute concentration is inversely related to water potential. For example, high solute concentration (of outside) = low water potential. I know that diffusion is the movement of solutes so that equilibrium in concentrations is equal on both sides. Therefore for osmosis, what’s being compared is the concentration of water on each side, which is also equivalent to the comparison of water potentials. With, for example, the outside of the cell containing more solute than the inside and the solute not being able to diffuse inward, this environment is called hypertonic, because it contains more solute. Therefore this environment has a low water potential, as the concentration is so high here. And because the rule is that water will go from high water potential areas to low water potential areas, the water will flow outward, causing the cell membrane and vesicle to shrink. By thinking one idea through I was about to draw in another idea and view these ideas as one whole concept, allowing me a well-understood general viewpoint.
I also think some other concepts would be helpful to review. In this section the Na+/K+ pump was mentioned step by step, so looking back to the diagram on p98-99 may be helpful. By the way, this example portrays active transport because a phosphate binds to the membrane protein, which symbolizes the use of energy. The binding of a phosphate from ATP will cause the pump to have a conformational change, spewing out the previously attracted Na+ ions, allowing for the acceptance of K+ ions. The phosphate leaves, causing another conformational change that spews out the K+ ions, resulting in the original protein state that previously accepted Na+ ions. I mentioned passive transport and active transport up above, but haven’t said anything really about it. Just a reminder: active transport requires an energy (one phosphate) source because molecules/ions are being transported against the electrochemical gradient. And passive transport does not require energy to transport molecules/ions because they aren’t being moved against the electrochemical gradient (because of increased entropy).
I’m anticipating questions that compare osmosis & diffusion, as well as comparing active & passive transport, in addition to the proteins and molecules they utilize, and maybe a reference to the Na+/K+ pump. I think I can make sense of pumps and diffusion, but may be getting mixed up with the types of proteins used in facilitated diffusion (especially transporters and cotransporters).
6.3: Why Molecules Move across Lipid Bilayers: Diffusion and Osmosis
Diffusion
•Movement from areas of high solute concentration to areas of low solute concentration
•Spontaneous process when along a concentration gradient, b/c entropy increase
•Concentration gradient→formed by a difference in solute concentrations (net movement)
•Equilibrium = even distribution of solute concentrations on both sides of semipermeable membrane
-Molecule/ion movement rate is at continuous, even rate
Osmosis
•Movement along concentration gradient (from high water concentration to low water concentration)
•Osmosis→ the movement of water across a semipermeable membrane
•Water moves from high water potential area to low water potential area
-Allows for dilution of higher concentration and equalizes concentrations
•Hypertonic→In comparison to inside, outside of cell contains higher concentration of solutes; water moves out of cell to dilute outside, causing cell shrinkage
•Hypotonic→In comparison to inside, outside of cell contains lower concentration of solutes; water moves into cell to dilute inside, causing cell rupture
•Isotonic→Outside solute concentration same as inside solute concentration; no change to cell
Membrane proteins
6.4: Membrane Proteins
Membrane proteins
•Allow the passage of ions and molecules those usually are unable to pass through the semipermeable membrane of the cell
-Due to charge or size
•Transport proteins allow permeability of membrane
•Allow environments outside cells to be quite different from inside environments
Passive transport
•Is powered by diffusion along an electrochemical gradient
•Ion Channels→Allow for ions to pass through membranes on their own
-From high to low concentration (diffusion); from different to similar charge
-Movement of ions influenced by electrochemical gradient
•Channel proteins
-Selective; carefully monitored
-Composed of certain structure; allows admission of certain kind of ion or molecule
-Ex: Gated Channel→open/close in response to binding of particular molecule, or to change in the electrical charge on outside of membrane
•Facilitated diffusion→passive transport of material that doesn’t readily cross the membrane
Active transport
•Bring in molecules/ions against electrochemical gradient
•Requires energy
-Stems from one phosphate group, from an ATP
•Goes against electrochemical gradient
•Pumps
-Change of shape allows ion/molecule movement against electrochemical gradient
-Set up electrochemical gradients, collecting/throwing out of certain chemicals
•Cotransport
-Gradient set up by pump; gradient becomes source of energy to allow movement of different molecule against the gradient
Hey everyone!
In chapter 37 we learned about Water and sugar transport in plants and the various mechanisms of water movement. The main things to take away from this chapter was the idea of water and solute potential and the various hypotheses of water and sugar transport . For example, an important concept would be that water moves from areas of high water potential to areas of low water potential. This is driven by 2 things, solute potential and pressure potential. Both of which you will need to have a good idea of, especially solute potential. This is connected to the idea of osmosis , which has to do with water movement through a semi permeable membrane. Know vocab terms such as isotonic and hypotonic. We also read about different types of soils, such as dry and salty soil. Know how these effect solute potential and how plants are able to adapt to these changes in soil. For example an oleander plant has several cell layers of epidermis to lower water loss which is why it thrives in dry environments. Review the cohesion-tension theory and the Pressure flow hypothesis of sugar transport.
Here is a brief outline:
• Transpiration: loss of water via evaporation from aerial parts of a plant
○ When stomata are open
○ Air surrounding the leaves are drier than air inside leaves
• Water potential: potential energy that water has in a particular environment
○ Differences in water potential determine direction the water moves
○ Moves from areas of high water potential to areas of water potential
• Isotonic: solute concentration in cell and outside cell are equal
• Osmosis: water movement in response to solute concentration through semi permeable membranes
○ Solute potential is seen in terms of solute concentration relative to water
○ High concentration in water=low solute concentration
○ Water moves from regions of low solute concentration to regions of high solute concentration
• Water potential in soils, plants and atmosphere
○ In dry soil, water does not float around freely
○ Water clings to soil particles thus creating negative pressure tjat lowers pressure potential of water
○ Species adapt to this by lowering the solute potential of root cells
○ Species in dry areas cope by adapting to dry areas
§ They are able to tolerate low solute potentials
§ Usually when soils dry, water potential drops but if solute potential goes down as well , it can maintain a water potential gradient that continues to bring water into plants
○ Limiting Water loss
§ Have adaptations that limit water loss
§ Help slow transpiration and limit water loss
§ For example oleander leaves have thick cuticle that covers the upper surface
§ Epidermis can be several layers deep
§ Stomata can be located in undersides of a leave, in deep pits of the epidermis, have hair like stuff on epidermal cells to protect from atmosphere
□ Hypothesis is that they slow loss of water vapor
§ Long thin leaves, smaller surface area
• Casparian Strip and Suberin
○ The Casparian strip is by the endodermis, endodermal cells are tightly packed and secrete a waxy substance called suberin, this waxy layer is called the Casparian strip
○ Purpose is to block water from moving through walls of endodermal cells
○ Important because it is the means that for water and solutes to reach vascular tissue , they have to move into the cytoplasm of an endodermal cell, the cells act as filter
• Root Pressure
○ Movement of water and ions result from this
○ One of the three hypothesized mechanisms for moving water up xylem
○ Stomata close at night, which results in minimization of water loss and slow movement of water into roots, roots still accumulate ions though
○ Move into xylem
○ Lowers water potential of xylem, below water potential of surrounding cells
○ Makes water move up into xylem from other root cells
○ Positive pressure generated, fluids build up in xylem
○ Guttation: occurs in low growing plants, water can move to force water droplets out of leaves, for example when we see dew on leaves in the morning
• Cohesion- Tension Theory
○ Leading hypothesis to explain long distance water movement
○ Check out the diagram in the book: Figure 37.10
○ Water is pulled from tops of trees along water potential gradient, via forces generated by transpiration
• Pressure Flow hypothesis
○ Events at source tissue and sink tissues create large pressure potential
○ Based on movement along water potential gradient created by changes in pressure potential
○ Check out Figure 37.17 for understanding on pressure potential
• Phloem loading and Unloading
○ Loading
§ to establish high pressure potential in sieve-tube members near source cells, a whole lot of sugar has to be transported into phloem sap to raise solute concentration
§ Pg. 731
○ Unloading
§ Sucrose is unloaded along concentration gradient into an important sink: young, growing leaves
§ Pg. 734
○ Phloem sap moves from areas of high water potential to areas of low water potential
• CHECK YOUR UNDERSTANDING
○ Pg. 734
Chapter 10: Photosynthesis
Photosynthesis Harnesses Sunlight to Make Carbohydrates
-Light Dependent Reaction vs. Light Independent Reaction
+Calvin Cycle is light independent
+The two reactions are connected by NADP+ which carries electrons from the light dependent reaction to the independent ones.
How Does Chlorophyll Capture Light Energy?
-Chlorophyll – Absorbs red and blue light
-Carotenoids – Absorb blue and green light
-Flavonoids – Absorb ultraviolet light and protect the plant
The Discovery of Photosystem II and I
-Photosystem II – Produces a proton gradient that drives the synthesis of ATP
1.Chlorophyll is hit by a photon
2.Pheophytin accepts the electrons from the chlorophyll
3.These electrons are passed onto the electron transport chain in the thylakoid membrane.
4.The electron transport chain sets up a proton gradient that drives ATP synthase
5.Photosystem II obtains electrons by oxidizing water
-Photosystem I – Produces NADPH
How is Carbon Dioxide Reduced to Produce Glucose?
-Calvin Cycle – Located in the stroma of chloroplasts
+Fixation Phase
+Fixes carbon to produce 2 molecules of 3-phosphoglycerate
-Reduction Phase
+3-phosphoglycerate is reduced by NADPH to form glyceraldehyde-3-phosphate(G3P) which can then be made into fructose and glucose
-Regeneration Phase
+The rest of the G3P keeps going through the cycle and acts as the substrate
-Rubisco – CO2 fixing enzyme
+Extremely inefficient enzyme that is very slow and can also catalyze O2 to RuBP which makes its CO2 fixing properties even more inefficient
The most important point of this chapter is to understand how photosynthesis actually works. Be able to answer questions such as:
What drives photosynthesis?
What are the products of photosynthesis?
What is the difference between photosystem I and II?
Be able to explain to someone else how photosynthesis works
Useful diagrams in the book are 10.14 on page 183, and 10.18 on page 186.
Helpful videos for understanding photosynthesis: http://youtu.be/-rsYk4eCKnA
I love khan academy thanks for posting this I forgot he did these videos and these will help me study
Also, some additional information on C4 and CAM plants which we only talked a little about in class.
Photorespiration is when O2 instead of CO2 is fixed to the RuBP which is a waste process for a plant.
In C4 plants the calvin cycle (aka light independent reaction) happens in bundle sheath cells which are deeper in the cell and not in the mesophyll. PEP acts as a ferry which ferries CO2 from the mesophyll to the bundle sheath cells. In this way the plant is able to isolate CO2 away from O2 so no photorespiration will take place. I have a more detailed summary below but this is the basic idea.
C4 plants are able to use a different process involving PEP carboxylase which selects CO2 and leaves O2 and fixes it to a 3 carbon molecule called PEP to make a 4 carbon molecule. This 4 carbon molecule then moves into what is called bundle sheath cells which are further in the cell and away from O2 and is broken back down into CO2 and the 3 carbon molecule PEP again. PEP then goes back into the mesophyll and does its thing with another CO2 and now we have isolated CO2 in a bundle sheath cell with no O2 so no photorespiration will take place. This is my summary of the process if you couldn’t follow you can look at this video…
CAM plants are like desert cacti. As you can imagine the desert is hot and cacti want to retain their water during the day so they want their stomata closed. But if you have your stomata closed then you can get CO2 during the day (which is when photosynthesis happens) when you really need it. CAM plants do something interesting at night. They open their stomata during the night, when they wont lose a lot of water, and gather CO2. They turn this CO2 to a 4 carbon molecule and store it in a vacuole and during the day this gets turned back into CO2 which can be used for photosynthesis. This is how CAM plants get passed the fact that their stomata are closed during the day.
If you have any questions about CAM plants heres the link I used to help me
Hi Guys,
Chapter 39: Plant Sensory Systems, Signals, and Responses
Signal Transduction:
• Plant senses through signal transduction which means the receptor receives a signal and changes the form from external signal to intracellular signal.
• Two types of signal transduction:
– Phosphorylation cascades-when a receptor receives a signal, it changes its shape which causes addition of phosphate from ATP to receptor or inactive protein to activate and this process continues down the cell or changes to second messenger.
– Second messenger-it happens when producing intracellular signal result in hormone binding or release from the storage. Calcium ions are usually second messengers and they are stored in vacuole.
• Hormones are tiny molecules in tiny concentrations, but they have a big results.
Phototropism:
• We spend almost half the lecture period talking about phototropism, movement of plants toward light so I would expect something similar will be on the exam. So going over the experimental designs we came up during class is not a bad idea. Maybe try coming up with your own.
• Phototropism caused by a hormone called Auxin. When plant was exposed to light, it bend forward to the light and Auxin moves away from light. This causes proton pump to pump proton against the electrochemical gradient into the extracellular matrix allowing pH enzymes to loosen up its structure for growth (it called acid-growth hypothesis).
• Plants shows phototropic response only if blue wavelength is present, because blue light is important for photosynthesis. Only the tip of shoots respond to the blue light and distribution of Auxin happens.
Guard Cell Opening:
• Signal: Sunlight (particularly blue light)
• Proton Pump: Making the cell more negative
• K+ enters the cell through their channel along electrochemical gradient and H+ and Cl- enters the cell through cotransporter.
• Water rushes in following the solutes, because there is low potential of water in the cell.
• Guard cell opens
Guard Cell Closing:
• Cl- leaving/ ABA stops ATPase
• K+ leaving
• Water rushes out following the solutes
• Guard cell closes
Chapter 38: PLANT NUTRITION
What’s up everyone. Here’s a summarization of Ch 38, covering the important sections and concepts that our teacher covered. I broke it down so that it’s easier to understand.
This question got me when our professor asked it to us so I’m going to ask it again. When a growing plant gets bigger, where does its mass come from? Is it soil, water, air, or sun?
-If you answered soil, water, or air, you are incorrect. Please go over 4/4/13 PowerPoint again.
Nutrients
96% of plants weight comes from carbon, hydrogen, oxygen. So for their nutrients, plants need carbon dioxide (CO2) and water (H2O), but also need some a variety of essential nutrients to help growth What does it mean to be an essential nutrient? Basically, it’s required for growth, bodily functions, and reproduction.
• Macronutrients: need large amounts of N, P, K for synthesis of proteins, carbohydrates, etc. -Nitrogen, Phosphorus, Potassium are also known as limiting nutrients: limits plants growth.
• Micronutrients: need small amounts for growth (e.g. iron, magnesium)
Question: Are you able to design an experiment to tell whether nitrogen, or phosphorus is the limiting nutrient in the plant? Could we tell whether a plant is lacking nitrogen or phosphorus just by looking at the color of its leaves?
Nutrient Availability and Uptake
The elements that are needed for plant growth are found in soil as ions: anion = – , cation = + . Anions are readily available but washes off easily, while cations bind to soil particles and can be released by cation exchange. Cation exchange is when H+ protons bind to the soil particles while simultaneously other cation nutrients like Mg+ for example gets released in return.
Now let’s go further into how these nutrient ions pass through the root hairs using a proton gradient. In this gradient, proton pumps are created where H+ ions (protons) are pumped out of the cell in order to allow other positive ions to come in via channels. As for negative charged particles, a proton is pumped out in order for an anion to be transported in with a proton through a cotransporter (basically, a proton holds the hand of the opposite charge in order to come in).
Plants have many different ways of obtaining their nutrients
• Bacteria can colonize on the root nodules of plants and mutually exchange nutrients with nitrogen fixation. A bacterium gets protection and sugar while the plant receives ammonia.
• Carnivorous plants can trap and digest different insects and animals. They can survive low nitrogen atmospheres because they easily obtain nitrogen through their food.
• Parasitic plants can attach itself to the xylem of host plants and steal nutrients and water.
Terms on plant quiz covered on chapter 38
(V) Metallothioneins: proteins that attaches itself to metal ions to stop it from poisoning the plant.
(V) Leghemoglobin: a protein that binds to oxygen in order to prevent it from poisoning an enzyme that’s needed for nitrogen fixation.
What is nitrogen fixation? It’s when bacteria or archaea can absorb N2 and convert it to ammonia, nitrite, or nitrate.
(V) Hydroponics: growth of plants in liquid, without soil. The availability of nutrients can be accurately controlled.
Hey guys! Here are some bulleted points of things that Bryan has been stressing throughout the quarter as well as some experimental questions to ask yourself while studying these 🙂
Chapter 36 Form and Function
Plants have a root and shoot system
Root Systems: The below portion of a plant that anchors ad takes in water and nutrients from the soil such as nitrogen, phosphorus and potassium. They absorb selected nutrients from soil, conduct water and nutrients to shoots and stores nutrients for later.
• The importance of Surface Area/ Volume
o A plant is more efficient as an absorbance and synthesis machine when it has a large surface area compared to its volume.
This is why most roots are long skinny tubes
• Taproot System
o Most plants have a vertical taproot with lateral roots branching off of it.
o example of taproot system
• Phenotypic differences
o Plants will change their shape if presented with an obstacle. For example, a tree in a water logged area will keep its roots close to the surface in order to get more oxygen and a tree in a dry area will have deep roots.
o How would you test this with a transplant test?
o How would you test this with a dose experiment?
• Diversity has its advantages
o Biologist have found that natural selection favors structures that minimize competition.
o This is shown through Figure 36.4 where it shows different Prairie plants that would live together. Each has a very different set of roots demonstrating that they are each searching for resources in a different area so they aren’t competing together.
o Experiment! How would you test this theory?
A way I would do it would be to find several plants that share the same basic root shape and plant them in a confined area, wait a few months and see if any had died out or if they modified their shape in order to coexist.
• Special Roots
o Ivy have roots that allow them to cling to walls
o Prop roots help support corn and keep them up off the ground
o Mangroves have little sprigs of roots popping up out of the ground for gas exchange.
o Contractile roots pull the plant deeper underground as if to plant themselves, many bulbs do this.
• Fun Facts!
o A researcher grew a winter rye plant for four months and then measured the roots. He found that it had a combined length of 11,000 km
o Roots of trees are often wider than their canopies
o It is not unusual for root systems to make up 80% of the plant’s overall mass
Shoot system: A repeating series of nodes, internodes, leaves, and buds.
• Anatomy
o Stems-above ground structures
o Nodes, where leaves are attached (internodes-area between nodes)
o Leaf- photosynthetic organs
o Branch-structure off of shoot system
o Apical bud- top bud
o Maybe flowers- reproduction sites
• Diversity!
o Just like roots, shoot systems also vary in order best use their energy for growth and not competition.
o This can be done with varying branch angles and different internode lengths.
Ex. Some are short and bushy, some are tall and slender
o How would you test this?
Transplant idea: take a plant that has been growing as a short bushy plant and put it in an area that had a lot of taller plants choking out its light. Observe it’s growth
o Different phenotypes. Plants will alter their shape for their environment
Ex. Different elevations
o How would you test this?
Move plants from different elevations and see if their growing patterns change.
o Special shoot modifications
Stolons- like strawberries
Tubers- like potatoes
Thorn- like blackberries
Rhizomes- like canary grass
• Leaves
o Growth patterns
Alternate
Opposite
Whorled
o Different types of leaves
Simple
Compound
Complex
Needles
(one node per leaf)
o Questions
What are the advantages to these different shapes of leaves?
Ch. 37: Water and Sugar Transport in Plants
Hi guys, chapter 37 contains a lot cool stuff. I try to highlight the important parts from both lecture and book. Key terms and summary with some aid of catch-up questions.
Transpiration: the loss of water through the stomata
What is water potential?
Transpiration occurs when two conditions are met:
1). Stomata are open, usually during the day when photosynthesis is occurring.
2). The air in the environment is drier than the air inside the leaves.
Water moves up a plant because of differences in the potential energy of water. Plants replace water by moving water up the plant by a water-potential gradient, the overall movement of water when a series of water potentials differences are contrasted. Plants tend to gain water from the soil and lose it to the atmosphere.
1) Water potential is the potential energy that water has in a particular situation compared to the potential energy of pure water at atmospheric pressure at the same temperature.
2) There is a water-potential gradient between the roots and the leaves.
3) Q: Water moves from areas of ____ water potential to areas of ____ water potential.
A: high; low
What factors affect water potential?
If you are familiar with the idea hypotonic, hypertonic and isotonic, Osmosis is the process by which water moves across the semipermeable cell membrane.
Iso means inside equals outside, hypo means inside greater than outside, hyper is inside less than outside.
Solute potential is the tendency of water to move by osmosis, defined by its solute concentration relative to pure water. Page 718, figure 37.1, has a better visual illustration.
Q: What are the two main factors that affect water potential?
A: Solute concentration and physical pressure
How to calculate the water potential?
It is quite easy to calculate the water potential, its unit is megapascal. Generally, water moves from higher water potential to lower water potential. The pressure potential from turgor pressure is positive inside cells; it thus increases the water potential and increases the probability that water will move out of the cell. In most situations, the water potential of plant cells is lower than that of the surrounding solution, water moves into cells.
Turgor pressure: the pressure that is exerted on the inside of cell walls and that is caused by the movement of water into the cell
Ψ = ΨS + ΨP; S=solute; P=pressure (i.e. water moves up trees by moving down the gradient)
Q: Solute potentials are always _______.
A: negative (because they are measured relative to to the solute potential of pure water, which is zero)
When positive turgor pressure plus the cell’s negative solute potential equals zero, the system reaches equilibrium. At equilibrium there is no net movement of water in/out of the cell.
Q: What three major hypotheses have biologists suggested for how water can be transported in a plant?
A: Root pressure, capillary action, cohesion-tension
Water movement via root pressure, pressure potential that develops in roots, could drive water up against the force of gravity. It is generated after the stomata closed.
1. The endodermis (inner layer) is responsible for root pressure.
2. During the night, the root accumulates ions taken up by the epidermal cells.
3. These ions are transported to the xylem, decreasing its water potential.
4. Water flows into the xylem, creating positive pressure and pushing the water up the xylem toward the leaves.
5. transpiration is low at night, the water being pushed into the leaves escapes through small pressure valves, resulting in guttation. (Fig. 37.8)
Xylem: vascular tissue that carries water upward from the roots to every part of a plant.
Capillary action: could draw water up the cells of the xylem. Capillarity occurs in response to three forces: surface tension, adhesion, and cohesion.
Cohesion-tension: force generated in leaves, could pull water up from the roots through the xylem. It is an explanation for the movement of water up the stem xylem of tall plants; states that water is pulled up the xylem vessels by the cohesive force between the water molecules and the adhesion of the water molecules to the rigid vessel walls.
Water transport is powered by solar energy in this process.
This webpage illustrates phloem. Sink is the part that tissue where sugar exits the phloem.
https://www.boundless.com/biology/water-and-solute-management-in-plants/sugar-transport-via-phloem/transport-from-sugar-sources-to-sinks/
Experiments on sugar-beet plants allowed researchers to track the movement of carbon atoms through plants to see the connection between sources and sinks.
Experiments showed there is a strong correspondence between the physical location of sources and sinks.
Pressure-flow hypothesis is that when nutrients are pumped into or out of the system, the change in concentration causes a movement of fluid in the same direction.
bulk flow: The movement of a fluid due to a difference in pressure between two locations (pressure gradient)
phloem loading: sucrose is moved by active transport from source cells through companion cells to sieve-tube members.
phloem unloading: companion cells move sucrose from the sieve-tube members into sink root cells by active transport, creating phloem sap with a low sugar concentration.
The net result of phloem loading and unloading is high turgor pressure near the source and low turgor pressure near the sink, which drives phloem sap from source to sink via bulk flow.
I was rushing through the chapter and slides we discussed in class. Welcome to help me adding more stuff that can help us better understand this interesting part in plant physiology.
the square is smiley face though.
Alright so I had experimental design as a topic and I’ll go through a few things trying to work it out and hopefully it’ll help you guys too. The main thing that Bryan stresses is variation when he gives you an experiment he doesn’t want to see 5 dose response experiments he maybe wants to see 2 dose response, as well as a control, rescue, take away that sort of thing.
Here is an experimental question I came up with…
You notice that corn seeds grown in light develop a long, thick, purple root (shut up I know what you’re thinking) with no branches while corn seeds grown in dark develop multiple thin roots with branches (yes this was from our experiment). What could be causing this to happen and what experiments would you do to find out?
So what do we have in our tool box to work with?
Control and negative control: Making sure that the seeds aren’t defective
Dose Response: Changing the amount that it gets to see if this has an influence
Take away: Taking something important away to determine if this specific thing is causing what you’re seeing.
Transplantation: transplanting an organ to see if this would cause the same effect.
Rescue: Giving the plant something vital it needs/ opposite of take away
Part 1: The first part would be to brainstorm what could be causing the issue. An obvious one is light but there is also heat (caused by light) or increased humidity caused by heat. These can all be translated into hypothesis that will help you in designing an experiment.
Part 2: The experiments…
Dose response: Again Bryan wants to see variation so we could do a couple experiments where we test corn in 6 hours of light and then again in 12 hours of light to see if this would cause the root to become purple and not spread out. This would be a dose response
Controls are easy you would just grow the corn in dark and light to make sure they will grow and your observation is reproducible
Take away: A good take away would be to grow the plant in light and then take this away about halfway through the experiment. This could show whether or not this change in variables would cause the root to begin to expand or not.
Another take away could be that you just take away other variables until you arrive at the last remaining one. You could take away the variable of humidity and keep them the same then you could take away the variable of heat by keeping this the same. This would allow you to see what exactly is causing the different root growth.
Rescue: A possible rescue for this would be to grow it in dark and then transfer it to light (technically you are rescuing the plant) to see if the root then changes into a purple root. This is the opposite of the take away experiment that we saw earlier
Transplantation: This one is easy you could transplant a purple root from a corn seed grown in the light to a corn seed grown in the dark and see if the root will continue to be a purple root or if the root begins to spread out and vice versa.
Let me know if you guys come up with any other experiments that you can think of or if you thought that I was totally wrong on one of the experiments.
Yipes! I wrote this all up yesterday and almost forgot to post it!
Core concepts in physiology
I’m going to try and give an example of something we have covered and connect it to the following core concepts.
1. Homeostasis
What jumped to mind immediately for me was osmosis and electrochemical gradients. Homeostasis is the tendency of a cell to regulate its interior to match the conditions of its exterior; to create a balance (homeo – stable; stasis – static).
Imagine a cell with a high concentration of solute inside and relatively low concentration of solute outside (the solution is hypotonic). The high water potential on the outside presses water across the membrane into the cell until the relative concentration of the solute is equal on both sides; until it is stable.
2. Cell membranes
In class we discussed how plant cells move important ions across membranes. Because ions do not travel easily across semi-permeable membranes they require the help of a few different types of proteins: channel, pump, transport, and co-transport. Remember, while all of these proteins allow the movement of ions across a membrane, only the pump requires the input of energy in the form of ATP.
3. Cell-cell communications
If you haven’t had a looked at the video of the sensitive plant, do it. It’s way cool. It’s also a great example of signal transduction. When a cell (plant or animal) receives an external signal (from another cell or the environment) a receptor protein will change conformation. This protein then catalyzes a phosphorylation (ATP in, ADP out). From here one of two things can happen: either a phosphorylation cascade is triggered (a series of proteins are phosphorylated over and over) or a second messenger is released (a stored or produced compound; the book uses Ca+ as an example). Ultimately this set of reactions with either release a hormone to be passed along to another cell (and the process starts over) or some other mechanism is triggered. I’d love to know what exactly the sensitive plant is responding to (heat, friction, etc.)…
4. Interdependence
Connections, connections, connections. For plants, mycorrhizae are my favorite example. This is the symbiotic connection between certain fungal species and over 80% of all plants. These fungi are more efficient at breaking down amino acids in the soil and absorbing other forms of nitrogen than the plants themselves. In exchange for the nitrogen that the fungi collect, plants trade out some of their photosynthetic byproducts; sugars. In this way, the fungi need the plants for their sugar and the plants need the fungi for their nitrogen.
5. Flow down gradients
Osmosis. In order to reach a homeostatic equilibrium, cells will exchange water across cell membranes until the relative concentration of solutes on one side is equal to the other. Think about the eggs in our break out group (and how I was apparently tasting each solution…). If there were more of a solute on the outside of an egg (the solution was hypertonic) all the water in the egg would flow out to reach an equilibrium (it got all shrivelly). The water moved from high water potential to low water potential.
6. Structure/function
Rhizomes. The potatoes that we all eat are actually parts of the stem of the potato plant (not in fact its roots). These specialized stems are ideal for storing carbohydrates (starches in the case of potatoes) and are what makes them such dense sources of nutrients. This size and position of the potatoes’ rhizome is important for its survival during the off season. When winter rolls around and the potatoes stop photosynthesizing, it relies on the stored sugars in the rhizomes until spring arrives and it can begin synthesizing new sugars.
7. Phenotypic plasticity
Phototropism. Phenotypic plasticity is the ability of an organism to change its physical characteristics in response to an environmental change. In the case of phototropism, remember that plants tend to grow toward a light source. This is caused by the presence of the hormone auxin which elongates the cell on the side of the plant furthest from the light. Auxin triggers a proton pump that acidifies the cell wall and “loosens” the fibers that make it rigid. Osmotic pressure makes the cells with loose cell walls bulge and expand making one side of the stem larger than the other causing it to lean toward the light.
I loved your explanations and connections to the class!
I’d love to know what exactly the sensitive plant is responding to (heat, friction, etc.)…
When you said that, it made me smile. What a good test question.
I need to think about phototropism as an example of phenotypic plasticity. On one hand it is right on, yet something doesn’t sit quite right with me. I think it is the time scale of the changes. Phototropism can occur within an hour. To me, phenotypic plasticity takes longer usually. But I don’t know why I lean that way. Just and FYI. Thanks for making me think.