Question

Which one of the following conditions is true for the state of stomata of a green leaf shown in the given diagram?

[1 Mark]

Answer 1

In the depicted figure, the stomata are in closed condition.

• The mechanism of the closing and opening of the stomata depends upon the presence of sugar and starch present in the guard cells.
• In the presence of light, the guard cells of the stomata contain sugar which is synthesized by their chloroplasts.
• The sugar is soluble and increases the concentration of guard cells.
• Due to higher concentration of the cytoplasm of guard cells, the water enters into these cells from the neighbouring cells by osmosis. Hence, the stomata remains open.
• In the absence of light the sugar present in guard cells converts into the starch. The starch is insoluble, and this way the guard cells remains in lower concentration than the of neighbouring cells. So, water from the guard cells moves out to the neighbouring cells by osmosis. This makes the guard cells flaccid and the stomata closes.
• So stomata closes when large amount of water flows out from the guard cells making option (c) correct.