Question

Fig. represents a structure found in a leaf. Study the same and answer the questions that follow:

1. Name the parts labelled A and B.
2. What is the biological term for the above structure?
3. What is the function of the part labelled A?
4. Mention two structural features of A, which help in the function mentioned in (c) above?
5. Where is this structure likely to be found in a leaf?
6. The structure helps in the process of transpiration. Explain the term transpiration.

Answer 1

1. 1. Guard cell
   2. Stoma
2. Stomata
3. The guard cells (A) regulate the opening and closing of the stomatal pore, controlling the rate of transpiration and gaseous exchange 
   between the plant and the atmosphere.
4. 1. The guard cells have thin outer wall and thick inner wall.
   2. Guard cells contain chloroplasts in their cytoplasm.
5. They are found in the epidermal layer (epidermis) of the leaf. In most dicot leaves, they are more abundant on the lower epidermis (abaxial surface) to minimise excessive water loss.
6. Transpiration is the loss of water as vapour from the aerial portions of a living plant.