Q1 of 67 Page 48

Give two examples of turgor movements in plants.

The two examples of turgor movements in plants are:

1. The rapid dropping of the leaves of the touch-me-not plant (Mimosa pudica) where if one of the leaves is touched, the leaflet folds up and the entire leaf droops. In these plants, the stimulus of touch leads to the loss of turgor at the base of the leaflets and consecutively the base of the petioles.


2. The sun facilitates the suction pull of water from the soil thus keeping the cells turgid in the morning by transpiration but soon the leaves wilt due to loss of turgidity during the night. Thus some plants show sleep movements at night due to the loss of turgor pressure.


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4

Give reasons for the following:

Potato cubes when placed in water become firm and increase in size.

 5

Mention whether the following statements are true (T) or false (F) and give an explanation in support of your answer.

(a) Plasmolysis is the reverse of deplasmolysis. (T/F)


(b) Guttation is another name for bleeding in plants. (T/F)


(c) Soaked seeds burst their seed coats. (T/F)


(d) If the phloem of a twig is removed keeping the xylem intact, the leaves of a twig wilt. (T/F)


(e) Guttation in plants occurs maximum at mid-day. (T/F)


(f) Dry seeds when submerged in water swell up due to endosmosis. (T/F)

 12

Explain the mechanism of closing and opening of the stomata.

 3

The concentration of mineral nutrient elements is higher inside the root-hairs than in the surrounding soil. How do roots take them in from the soil?