Question

The figure given below is a transverse section of an old woody stem. It shows very minute openings labelled-A on its surface.

1. What are these tiny openings called?
2. Mention two significant functions of these openings.
3. Name two other tiny openings which can be found on the surface or margins of leaves.

Answer 1

1. Minute openings on the bark of woody stem through which transpiration occurs are called lenticels.
2. 1. Cooling effect: Evaporation reduces temperature of leaf surface. Therefore, transpiration is useful to plants on hot sunny days. (At intense heat, the enzymes are destroyed).
   2. Distribution of water and mineral salts: Since leaves are present at the tips of all branches and twigs, transpiration from their surfaces tends to draw water towards them and thus helps in the distribution of water throughout the plant body. Higher the rate of transpiration, greater the rate of absorption of water and solutes from the soil.
3. 1. From the leaves through the stomata (stomatal transpiration).
   2. Directly from the surface of the leaves and stems (cuticular transpiration).