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12 Cards in this Set
- Front
- Back
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31.4 What are the stimuli that control the opening and closing of the stomata? |
(Refer to stimuli for Opening and Closing) |
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31.4 What mechanism by which the activation of proton pumps could lead to severe wilting? |
Activating proton pumps takes up K+. Increased turgor of the guard cells locks open stomata & lead to extreme evaporation. |
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31.4 Why transfer flowers to a vase with wet cut ends? |
If transferred w/o getting wet, air pockets in xylem prevent delivery of water from the vase to the flowers. |
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31.4 Why does the evaporation of water from leaves lower their temperature?
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Because liquid temperature is related to average KE of its molecules, the temperature drops. The higher KE = lower temperature |
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31.5 Compare and contrast the forces that move phloem sap and xylem sap over long distances |
in both cases, the long distance transport is a bulk flow driven by a pressure difference at opposite ends of tubes. Pressure is generated at the source end of a sieve tube by the loading of sugar and resulting osmotic flow of water into the phloem and this pressure pushes sap from the source end to the sink end of the tube. in contrast transpiration generates a negative pressure potential as a force that pulls the ascent of xylem sap |
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31.5
Identify plant organs that are sugar sources, organs that are sugar sinks, and organs that might be either. explain |
the main sources are fully grown leaves (by photosynthesis) and fully developed storage organs (by breakdown of starch). roots, buds, stems, expanding leaves and fruits are powerful sinks because they are actively growing. A storage organ may be a sink in the summer when accumulating carbohydrates, but a source in the spring when breaking down starch into sugar for growing shoot tips
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31.5
why can xylem transport water and minerals using dead cells, whereas phloem requires living cells? |
positive pressure, whether it be in the xylem when root pressure predominates, or in the sieve tube elements of the phloem, requires active transport. Most long distance transport in the xylem depends on bulk flow driven by negative pressure potential generated ultimately by the evaporation of water from the leaf and does not require living cells.
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31.5
Apple growers in japan sometimes make a nonlethal spiral slash around the bark of trees destined for removal after the growing season. This practice makes the apples sweeter. Why? |
the spiral slash prevents optimal bulk flow of the phloem sap to the root sinks, therefore, more phloem sap can move from the source leaves to the fruit sinks, making them sweeter.
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31.1 If you prune a plants shoot tips, what will be the short term effect on the plants branching and leaf area index? |
pruning the shoot tips will not end their apical dominance allowing axillary buds to grow into lateral shoots (branches). This branching will produce a bushier plant with a higher leaf area index.
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31.1 Some plants can detect increased levels of light reflected from leaves of encroaching neighbors. This detection elicits stem elongation, production of erect leaves and reduced lateral branching. How do these responses help the plant compete? |
Increased stem elongation would raise the plant's upper leaves. erect leaves and reduced lateral branching
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31.2 How would the long distance transport of water be affected if vessel elements and tracheids were alive at maturity? explain. |
If tracheids and vessel elements were living cells, their cytoplasm would impede water movement preventing rapid long distance transport.
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31.2 What would happen if you put plant protoplasts in pure water? explain. |
The protoplasts would burst. Because the cytoplasm has many dissolved solutes, water would enter the protoplast continuously without reaching equilibrium (when present, the cell wall prevents rupturing by excessive expansion of the protoplasts
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