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18 Cards in this Set
- Front
- Back
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Define stomata
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Tiny openings in the leaf to exchange gases |
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Define transpiration |
The loss of water vapor from the stems and leaves of a plant |
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Explain the transpiration pull of water
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* sunlight causes the evaporation of water from the leaves * new water is absorbed by the roots, creating high pressure in the roots and low pressure in the leaves * the low pressure in the leaves draws water upwards to the leaves. |
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How can a plant regulate water loss?
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By the opening and closing of the stomata to control the amount of water lost to vapor |
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What are some factors affecting transpiration rate?
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Temperature Humidity Light intensity Wind exposure |
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Describe xylem structure |
* composed of hollow dead cells * multiple pores (pits) to allow water transfer between cell * walls are reinforced with cellulose and lignin |
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How is the cohesion and adhesion of water used to transport water in the xylem? |
Cohesion - water molecules form hydrogen bonds between themselves, puling them upward
Adhesion - The xylem wall is polar so water binds to it easily |
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How is water absorbed by the roots? |
By the active transport of mineral ions to create a high particle gradient in the root, causing water to move into the root by osmosis |
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What particles does typical fertile soil contain? |
Negatively charged clay particles to which mineral ions attract |
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How can mineral ions be displaced from the soil to be diffused into the roots?
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H+ ions are actively transported out of the cell, |
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What is a potometer? |
A device used to measure and estimate transpiration rates by measuring rate of water loss/uptake
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What happens in photorespiration? |
If there isnt enough CO2 (because the stomata are closed to conserve water), RuBP is oxygenated by Rubisco, leading to energy from photosynthesis to be wasted |
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How do CAM plants conserve water? |
* Only open stomata at night * After absorbing CO2, the convert it into malic acid * malic acid is broken down in the calvin cycle |
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What are phytochromes? |
Leaf pigments that are used to detect periods of light and darkness
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Which type of phytochrome is capable of causing flowering? |
Active phytochrome (Pfr) |
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How does (Pr) turn into (Pfr) and vise versa? |
* inactive Pr activates after light absorption and turns into activated Pfr. * Pfr will gradually revert to the inactive Pr in the absence of light / in darkness |
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In short-day plants, what is the role of Pfr? |
Pfr inhibits flowering, therefor the plant can only flower when the night period exceeds a critical length, and Pfr levels remain low |
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In long-day plants, what is the role of Pfr? |
Pfr activates flowering, therefor the night period needs to be less than a critical amount, there needs to be enough daylight hour to produce enough Pfr. |
