Page 97 - Science Class 07

In the deserts, the soil is deficient in water.
Therefore, the plants found in the deserts
have modified their leaves into thorns to
reduce the rate of transpira on so that they
could survive even in scarcity of water.

Transpira on process through leaves.
Effects of Transpira on
v Transpira on creates low pressure in upper
por on of the plants that helps in
transporta on of water and minerals
upward.

v It is responsible for maintaining turgidity
and thus helps in growth of plants.
v It has cooling effect on the plant and
maintains proper temperatures for other
physiological ac vi es.
v When the rate of absorp on is lower than 1. What is transpira on?
the rate of transpira on, the leaves of the
2. Why transpira on is useful?
plants are droped down and start wil ng.
3. Why do plants start wil ng?
4. How can we save plants from wil ng?

Plants also lose excess water in the form of
liquid. This loss of water in the form of liquid
of droplets occurs along the margins of the Aim : To show that plants carry on the
leaf through special structure, called process of transpira on.
hydothodes, is known as gusta on.
Take a small po ed plant and cover the soil
v The temporary wil ng occurs in the a er- of the pot with a polythene. Now, cover the

noon when the rate of transpira on is plant with a big glass jar. Keep this setup in
much higher than the rate of water the sunlight for a few hours.
absorp on. Plants recover in the evening You will observe that water droplets on the
when the rate of transpira on is slower inner walls of the glass jar.
than the rate of water absorp on. Actually, during transpira on water from the

v Permanent wil ng occurs in the region leaves is released in the form of water
where soil is deficient in water. It usually vapour which condenses when come in
kills the plant unless the soil is watered contact with the inner wall of the jar. This
soon a er the appearance of the first
symptoms of wil ng.

Science-7 97