Unit 1 Problems Sets Flashcards
what is the meaning of “Urpanflanze?” What modern biological characters would we use to define the group this concept represents
“primal” or “archetypal” plant. Cell walls, large vacuole, special sterols, chloroplasts, plasmodesmata, ergastic substances
provide two different explanations for why these graphs have different shapes
The units and scales are different for the x-axis. The left graph examines water absorption by the plant, while the right one reports rainfall, which may or may not be taken up by the plant. The difference in scale does not allow the viewer to determine if the left graph has an asymptote as is observed in the right graph.
is capillary action sufficient to transport water throughout a 20 cm tall plant?
Yes. A conduit diameter <74.5 um will create enough forces for water to rise 20cm
A researcher observes that transpiration stops when it begins to rain. After 15 minutes, transpiration commences even though it continues to rain. Explain why transpiration stops when it begins to rain and why it begins again after a short while.
When it is raining, the concentration of water vapor both in and outside of the cell are equal because water saturates the air and the leaf and environment are at the same internal and external temperature. Since there is no difference in water vapor concentration, transpiration stops. Transpiration recommences after some time because the internal temperature of the leaf begins to rise, causing the saturation vapor pressure within the air spaces in the spongy mesophyll to rise. As a consequence, water vapor begins to diffuse out through the stomata and transpiration resumes.
Cavitation often occurs during water stress. When an embolism occurs in a vessel element, how far does it spread? What prevents it from spreading further and how does this work?
Embolisms often remain in a single vessel element. In order for them to spread the air bubble must pass through pit membranes between vessels (sometimes including a torus/margo). Because these pits are tiny in diameter there is high surface tension and the water in the adjacent vessel is under great tension. Ultimately the pressure difference between the water filled side of the pit and air bubble keeps the embolism from spreading.
Describe the enzymatic mechanism of ion transport through carrier and channel proteins. Explain the difference in enzyme kinetics between these transporters.
Both channel and carrier proteins are passive transporters. Channels are protein covered pores that rapidly transport ions in response to an electrochemical potential gradient. They are typically specialized for inward or outward transport, but not ion specific. These are over 100x faster than carrier proteins, which do not have a pore that extends through the membrane. Ions bind to carrier proteins and drive a conformational change that moves the ions across the membrane. They typically have a high affinity for a specific ion, with low to no affinity for other ions.
Describe an experiment that determines what elements a plant absorbs. In addition, describe how physiologists determine what minerals are essential. Why do these need to be different experiments?
Hydroponic experiments are ideal for testing nutrient uptake and deposition. To test for update, apply a nutrient solution in high concentration to the growth medium, analyze bulk tissue for concentrations of each nutrient. However, this experiment would not tell us whether the nutrient are beneficial for the plant. To test this, we would systematically remove nutrients one at a time and look for signs of deficiency or total disruption of the plant life cycle (essential nutrients are needed to complete life cycles of all plants).
What is osmotic adjustment and how does it work?
Osmotic adjustment is the movement of solutes across a membrane to reduce the solute potential of a cell/cells effectively driving water movement (due to water potential gradients) into the cell. Primary or secondary transporter protein pumps actively move ions across the membrane against a concentration gradient usually through the generation of a proton motive force by H+-ATPase
Soil analysis indicates an element is present in the soil, yet plants grown in this soil exhibit symptoms of mineral deficiency for this element. Provide two explanations for this observation.
Soil pH is too high or too low making the nutrient inaccessible to the plant. The plant is water stressed such that apoplastic uptake is limited. If the plant is stressed for another nutrient or light, energy required for enzymatic extraction from negatively charged soil particles may be limited. The plant is deficient in a different essential nutrient that produces the same symptoms.
Your roommate’s prized orchid is sick! She needs your plant physiology expertise. You notice the orchid appears to be making new leaves, but those leaves are showing signs of chlorosis. The old leaves seem healthy. What nutrient(s) do you tell her to feed her plant? How do you know?
Immobile nutrients, e.g., S and Ca. Mobile nutrients would be moved to supply new leaves
