Page 91 - Biology - XII

SECTION - B

Investigatory Projects
Investigatory Projects

PROJECT - 1

Objective
To fi nd out T/A (transpiration and absorption ratio in various plants).

Principle/Theory
1. The loss of water in the form of water vapour from the Green plant
living aerial parts of plant is called transpiration. It is
regulated by the guard cells.

2. It takes place through stomata, lenticel or cuticle. It
is a controlled process, lowers down the leaf surface Cotton
temperature and also protects the young leaves from heat
of the sun or from sun burning. Bottle Oil

3. It is advantageous to plants in many ways. Scale
4. It is unavoidable and a dangerous process for plants as Water Water
well. Millions of plants die every year because of the Side tube
transpiration which exceeds the amount of water absorbed
by the plant through the root. It needs energy also.

5. The thermal emissivity (physical loss of heat) prevents Transpirometer
serious injury in all plants.
Fig. 1.1: Transpiration and absorption ratio
Materials Required
Absorb transpirometer, plants, water oil, pan balance and weights, and vaseline

Procedure
1. Take the absorb transpirometer apparatus and fi ll it with water.

2. Add a little oil on water in the side-graduated tube.
3. Insert a small plant with its roots intact. Use cotton to fi x the plant.
O r
Fix the cork with the plant to the bottle and make it air tight by applying little grease/vaseline.
4. Note the level of the water in the side-graduated tube.

5. Weigh the whole arrangement in a pan-balance and note the weight.
6. Keep the set for sometime in diff erent conditions and note the changes in the water level of the
side-graduated tube.
7. Also, take the weight each time and note it.
8. Repeat the process for other plants and compare the results.

90