Question

The rate of transpiration was determined under normal conditions in the laboratory. Giving reasons, explain the differences you would expect if the measurements were repeated under the following conditions.

1. The shoot is placed close to the heat source 
2. Some leaves are removed
3. The shoot is placed in a current of air created by a fan 

Answer 1

1. The rate of transpiration would increase. Because heat causes temperature to increase hence increasing the rate of evaporation of water from mesophyll cells of the leaf and reduces relative humidy of the air outside the leaf .
2. Rate would decrease . Because removal of the leaves reduces the surface available for transpiration.
3. Rate would increase. Because moving air washes away layers of water vapour immediately outside the leaf. This lowers humidity of air outside the leaf thus increasing the relative humidity difference (saturatiry deficit) between the inside and outside of the leaf.