How would you explain any difference in transpiration rate b

How would you explain any difference in transpiration rate between a normal leaf and one treated with petroleum jelly? What normally occurs in a plant leaf when water must be conserved? Assuming the stomata are open, under what environmental conditions would you expect the lowest rate of transpiration? Would you expect to find well-developed stomata and a cuticle on aquatic plants that spend their entire lives underwater? Why (or why not)?

Solution

I. If a leaf is covered with petroleum jelly,the rate of transpiration willbe greatly reduced because the petroleum jelly will close the stomata and will prevent the evaporation of water from the surface of the leaf.In contrast the leaf without petroleum jelly will show normal rate of transpiration.

2. When there is less water there are certain modifications in the leaves such as the leaves become hard,thick,with fewer stomata.The stomata are present only on the lower surface of the leaf.A cooling effect is produced by the presence of trichomes in the leaves,these increase the humidity on the surface of the leaf.Plants usually present in the desert conditions have sunken stomata inorder to reduce the loss of water.The leaves can also become curled inorder to reduce the exposed surface area.

3. Rate of transpiration is reduced when the temperature is low,the surroundings are humid,there is no wind,the light supply is dim.

4.The aquatic plants do not have cuticle as cuticle prevents loss of water.Most aquatic plants such as hydrophytes do not have stomata.The surface cells absorb water,nutients,dissolved gases from the surrounding water.Hydrophtes have poorly develped vascular tissue.