Question

For the process of destarching, leaves are kept in the dark for about
A) 2-4 hours
B) 30-40 minutes
C) 24-48 hours
D) 3-4 days

Answer 1

Destarch is one of the preliminary steps in a photosynthesis experiment. Photosynthesis is the process by which green plants can convert light energy into chemical energy.

Complete answer:
Destarching occurs in plants when the plant is deprived of starch. In this process, the starch reserves in a plant are depleted by depriving the plant of either light or carbon dioxide.

Option A: If a plant is kept in dark for 2-4 hours, destarching of leaves won’t occur as leaves can be destarched by depriving them of light from an extended period of time, i.e., 24 to 48 hours. Therefore, this is an incorrect option.
Option B: If a plant is kept in dark for 30-40 minutes, destarching of leaves won’t occur as leaves can be destarched by depriving them of light from an extended period of time, i.e., 24 to 48 hours. Therefore, this is an incorrect option.
Option C: Starch reserves are depleted from the plants when it is kept in low light intensity such as in a dark cupboard. Starch reserves may also be depleted when the plant is deprived of carbon dioxide. Usually, leaves can be destarched by depriving them of light for an extended period of time, i.e., 24 to 48 hours. It is done by keeping the plant in a dark place for a long period of time. In a dark place, photosynthesis does not occur and stored starch is used up, thus the plant is destarched. Therefore, this is the correct option.
Option D: If a plant is kept in darkness for 3 to 4 days then it will eventually die. It is so because, for the process of photosynthesis, sunlight is required. Therefore, this is an incorrect option.

Thus, the correct option is (C) 24-48 hours.

Note: It is to be noted that during the experiment of destarching, potted plants are convenient to work with as they can easily be placed in a dark cupboard, or under a bell jar draped with a black cloth.