Page 70 - Science Class 07

v At night, when it is dark, photosynthesis
comes to an end, but the process of
respira on con nues. As a result, plants
take in O and release CO . That is why
2 2
people are not advised to sleep under a

tree during the night.
How Different Parts of Plants Respire?

Roots : Roots take in oxygen present in the

gaps of soil par cles by the process of
diffusion. The root hair help in the process of
Aim : To show that germina ng seeds
diffusion. The oxygen diffused through the root
produce heat during respira on.
hair passes into the roots and end product CO
2
also moves out through the root hairs. Materials required : Some seeds of beans,
water, two test tubes and a thermometer.

Method : Soak the seeds of bean in water
over night so that they could start germin-
a ng. Separate half of the total seeds and
boil them to stop their germina on. Now,
take the live germina ng seeds in a test tube
and keep the boiled seeds in another test
tube. Insert a thermometer in each test
tube. Close the mouth of both the test tubes
with the help of moist co on.
Stems : The stems of plants have special

openings called len cels. These len cels help in
the exchange of CO and O and the process of
2 2
respira on is carried on in the stem.

Note down the readings in the temperature.
Leaves : The surface of the leaves have small
Leave both the test tubes for 1-2 hours and
pores in them called stomata. Through the
again note down the readings in the
process of diffusion O enters in to the cells of temperature.
2
the leaves when the concentra on of CO
2
increases in the cells, the stomata opens to You will observe that the temperature in
release it into the atmosphere. which the germina ng seeds were kept has

70 Science-7