2016 · Q11
How is the rate of transpiration affected by decreasing humidity and by decreasing light intensity? (Columns: Decreasing humidity | Decreasing light intensity)
general-sciencebiology-plants
- ADecreases | Decreases
- BIncreases | Decreases
- CIncreases | Increases
- DDecreases | Increases
Explanation
Decreasing humidity steepens the water-vapour gradient between the leaf interior and the air, so the rate of transpiration increases. Decreasing light intensity causes stomata to close and slows photosynthesis, so transpiration decreases. The two factors therefore act in opposite directions: increases with falling humidity, decreases with falling light.