Question

Given below are the diagrams of a certain structure in plants in two conditions. [5 MARKS]

(a) Name the structure shown in the diagram.
(b) Name the parts numbered 1 to 5.
(c) What is the most apparent difference between A and B in the structure shown?
(d) Describe the mechanism which brings about the change in the structure depicted in A and B.

Answer 1

a) 0.5 Mark
b) 2.5 Mark
c) 1 Mark
d) 1 Mark

(a) Stomata is shown in the diagram.

(b)
(1) Chloroplast
(2) Inner wall of stoma
(3) Nucleus
(4) Guard cell
(5) Stoma

(c) The stoma is open in A and is almost closed in B.

(d) The opening and closing mechanism of stomata is regulated by the amount of water and solutes present in the guard cells. Guard cells contain chlorophyll and no other epidermal cells contain this pigment. Therefore, in presence of sunlight, chlorophyll gets activated and synthesizes glucose which increases the osmotic concentration. So the cell absorbs water from the next turgid cell and opens out due to high turgidity. Hence the stoma opens. At night, the photosynthesis stops and guard cells turn flaccid due to the loss of water and the stoma closes.