| Why does transpiration happen | side effect of stomata being open for gas exchange |
| What causes stomata to open and close | Guard cells, they are thicker inside and thinner outside causing them to curve inwards when osmosis occurs and water enters. |
| How does light intensity affect transpiration rate | the lighter it is the faster the transpiration rate. This is because the stomata open when it gets light so carbon dioxide can diffuse into the leaf. |
| How does temperature affect transpiration rate | the higher temperature the faster the rate of transpiration. Water molecules have more energy so they evaporate from cells faster. This also increases the water potential gradient between the inside and outside of the leaf |
| How does humidity affect transpiration rate | the lower the humidity the faster the rate of transpiration |
| How does wind affect transpiration rate | the windier it is the faster the transpiration rate |
| How do you use a potometer | 1) cut shoot under water (prevents air entering xylem) and at a slant (increases SA available for water uptake)
2 assemble potometer in water and insert the shoot underwater, so no air can enter
3) remove end of capillary tube from the beaker until one air bubble has formed and put the end back into the beaker
4) record the starting position of the air bubble
5) start stopwatch and record the distance moved by the bubble per unit time |
| What are xerophytic plants | Plants that are adapted to live in dry climates, such as cacti and marram grass |
| How has catci adapted to survive | - they have a thick, waxy layer on the epidermis
- this reduces water loss by evaporation because the layer is waterproof-
- they have spines instead of leaves, this reduces surface area for water loss
- they also close their stomata at the hottest time of the day when transpiration rates are highest |
| What are hydrophytic plants | Plants that live in aquatic habitats, such as lilies |
| How have hydrophytic plants adapted to survive | - air spaces in their tissue help them to float and act as a store for oxygen for respiration
- stomata are usually only present on the upper surface of floating leaves
- flexible stems and leaves prevents damage from water current |
