Question

A stomata closes when : (i) it needs carbon dioxide for photosynthesis. (ii) it does not need carbon dioxide for photosynthesis. (iii) water flows out of the guard cells. (iv) water flows into the guard cells. The correct reason(s) in this process is/are :

The maintenance functions of all living organisms must go on even when they are not doing anything particular. Even when we are just sitting in a class or even asleep, this maintenance job has to go on. These maintenance processes require energy to prevent damage and break-down of cells and tissues, which is obtained by the individual organism from the food prepared by the autotrophs, called producers.

In the experimental set-up shown above in diagram (I) atmospheric air is being passed into lime water with a syringe while in diagram (II) air is being exhaled into lime water. The time taken for the lime water to turn milky in both the test tubes is different. Give reason.

Draw the diagram of an open stomatal pore and label (I) Guard cells, and (II) Chloroplast on it. Mention two functions performed by stomata.

Assertion (A) : Most of the plants close their stomata at night. Reason (R) : Closing of stomata helps to conserve water as large amount of water evaporates from the leaves.