i. When plants perform photosynthesis,
they produce carbohydrates. These carbohydrates are used for their growth and
energy.
ii. The unutilized carbohydrates are
stored in the form of starch.
iii. While performing experiments on
photosynthesis, it is necessary that this stored starch is completely used up.
iv. When the plant is kept in dark, it
utilizes this stored starch and becomes destarched.
v. The factors essential for
photosynthesis such as carbon dioxide, sunlight and chlorophyll can be studied
with such destarched plant. Thus, the plants are kept in dark before
determining the factors essential for photosynthesis.
