17748624
Description
Flashcards by Sam Gunnell, updated more than 1 year ago
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Created by Sam Gunnell
about 5 years ago
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| Question | Answer |
| Define transpiration | The loss of water vapour from the upper part of the plant, especially the leaves (must say "water vapour" not just "water") |
| What part of the leaf limits evaporation? | Waxy cuticle |
| What are the three processes of transpiration (in order)? | 1) Osmosis 2) Evaporation 3) Diffusion |
| Explain how osmosis is involved in transpiration? | The water enters the mesophyll cells via osmosis via the symplast and apoplast pathway |
| Explain how evaporation is involved in transpiration? | The water evaporates from the surface of the mesophyll cells into air spaces between mesophyll cells, increasing the water potential |
| Explain how diffusion is involved in transpiration? | When the water potential is higher inside the leaf than outside, water diffuses out of the leaf via the stomata |
| Why does water leave the leaf via diffusion rather than osmosis? | There is no membrane so can't be osmosis as the water leaves via the stomata, not aross a membrane |
| Why do stomata open? | When the water enters the guard cells via osmosis, the guard cells become turgid, opening the stomata |
| How d guard cells decrease the water potential? | They actively pump in K+ ions |
| What apparatus is used to measure the rate of transpiration of a plant? | Potometer |
| How do you use a potometer? | Fill up the potometer with water and take a fresh shoot and cut it underwater at a slant. Keeping everything underwater, put the shoot into the potometer. Put vaseline on all the joints of the potometer and then dry off the leaves and leave them for a bit. Adjust the capillary tube so that the water is at the start of the scale and measure how far the water moves in a set period of time |
| Why must we ensure that we dry the leaves? | So that transpiration can occur |
| Why must we cut he shoot underwater and ensure no air bubbles are in the system? | So that the xylem can maintain a continuous column of water |
| Why must we leave the leaves for a bit before conducting the experiment? | So that the stomata can start to open and close |
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