1911179
Description
Flashcards by Danielle-May, updated more than 1 year ago
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Created by Danielle-May
almost 10 years ago
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| Question | Answer |
| What is transpiration? | Transpiration is the loss of water, by evaporation and diffusion, from the plant's surface, especially them leaves. |
| How is the transpiration stream created? | Evaporation causes a water shortage in the leaves, to replace this, water is drawn up the xylem vessels from the roots. Therefore there is a constant transpiration stream of water through the plant. |
| How is transpiration caused by diffusion? | Leaves have stomata for gas exchange. Because there's more water inside the plant than the air outside, the water escapes through the stomata by diffusion. |
| How is the transpiration rate affected by light intensity? | The darker the light, photosynthesis can't occur, stomata close as they don't need to let carbon dioxide in, water can't escape, lesser the rate of diffusion. |
| How does temperature affect the rate of diffusion? | The warmer it is, the water particles have more energy to evaporate and diffuse out of the stomata, the greater the transpiration rate. |
| How does wind speed affect the transpiration rate? | The lower the wind speed, water vapour surround the leaf, high concentration outside the leaf and inside the leaf, diffusion happens slowly, the slower the transpiration rate. |
| How does humidity affect the transpiration rate? | The more humid the air, the less difference in water concentration, diffusion happens slowly, the slower the rate of transpiration. |
| Wha piece of equipment can be used to estimate the rate of transpiration? | A potometer |
| How does a potometer work? | It estimated the transpiration rate, by measuring water uptake, assuming uptake is directly related to transpiration. |
| Why does the first step of measuring transpiration rate, include cutting a shoot underwater at a slant? | Cutting underwater will prevent air from entering xylem (air bubbles will affect results). Cutting a slant increases surface area for water uptake. |
| How do you set up the potometer? | 1- assemble potometer in water, and insert shoot under water. 2- remove apparatus from water, but keep capillary tube submerged in beaker of water. 3- check apparatus is water/airtight 4- dry the leaves and shut the tap 5- remove capillary tube from water until an air bubble has formed, then replace it |
| Once apparatus is set up, how do you measure the rate of transpiration? | 1- record the starting position of the air bubble 2- starts a stopwatch and record distance moved by bubble per hour 3- keep them conditions constant e.g. Temperature/air humidity |
| How can you see how environmental conditions affect transpiration rates? | Set up a control and a varied environmental condition, so you compare the two and see the change affected the transpiration rate. |
| What equipment can you use to change environmental conditions? | 1- lamp or cupboard 2- room that's cooler/hotter 3- spraying a little water into a clear plastic bag, before sealing it around the plant 4- fan |
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