Objective. To demonstrate that anaerobic respiration takes place in absence of air. Objective. To demonstrate phototropism (effect of unidirectional light on plants).Objective. To demonstrate the phenomenon of apical dominance.Objective. To demonstrate suction due to transpiration.

EXPERIMENT 10.1

Objective. To demonstrate that anaerobic respiration takes place in absence of air.

 REQUREMENTS -Germinating seeds, test tube, petridish, mercury, KOH

PROCEDURE:-Take the germinating seeds in a test-tube and fill the tube with mercury. Now invert the tube in a petridish of mercury with the help of your thumb. After sometimes, the level of mercury falls down in the test-tube showing that some gas has collected there. Introduce a crystal of KOH by means of a forceps. The gas will be absorbed and the level of mercury will rise again.

RESULTS:-The fall of mercury in the test-tube is due to the release of a gas by the respiration of the seed in absence of air. The gas is carbon dioxide because it can be absorbed by KOH. This shows, that anaerobic respiration takes place in the germinating seeds in absence of air.

PRECAUTIONS:-

1.The month of the test-tube must be smooth.

2. The dish for mercury should be deep.

3.Do not touch KOH with hand.

EXPERIMENT 10.2

Objective. To demonstrate phototropism (effect of unidirectional light on plants).

REQUIREMENTS A potted seedling of a plant, heliotropic (phototropic) chamber with a small hole on one side.

PROCEDURE Take a potted seedling of a plant. Place it in the heliotropic (phototropic) chamber. Close the top of the chamber. Place the experimental setup in a position that allow sufficient light to pass through the hole. Keep the setup undisturbed for a couple of days.

RESULT The tip of the seedling shows a bending (curvature) towards the hole (i.e. source of light). This shows that stem is positively phototropic.

PRECAUTIONS

1.Light should enter into the chamber only through the hole.

2.The soil of the pot should contain adequate moisture. 

EXPERIMENT 10.3

Objective. To demonstrate the phenomenon of apical dominance.

REQUIREMENTS  Two potted plants, knife. 

PROCEDURE: Take two potted plants of the same species. Cut off the apical (terminal) bud of one of the plants. Place the plants in open for few days.

RESULTS:-The lateral buds of the plant in which the apical bud has been removed, grow rapidly and the plant appears bushy while, the lateral buds in the plant with intact apical bud do not sprout and the plant continue to grow straight way. This shows that presence of apical bud suppresses the growth of lateral buds.

PRECAUTION

1. The potted plant should be approximately of the same size.

2. Pots should be watered regularly.

EXPERIMENT 10.4

Objective. To demonstrate suction due to transpiration.

REQUIREMENTS:- A long glass tube, rubber tubing, fresh leafy shoot cut under water, water, mercury, beaker, stand, rubber solution.

PROCEDURE:-Fill the glass tube with water. Close one end of the tube with your finger. Fix a short piece of thick rubber tubing over the other end. Through it insert the cut end of the shoot in the tube. Make the connection air tight with rubber solution. Dip the free end of the glass tube in a beaker containing mercury. Hold the tube vertical by means of a stand. Place the experimental set up in open place.

RESULTS:-Soon mercury rises upwards in the tube. The size of mercury in the tube clearly shows that water in the tube is being pulled upward with a great force. This pull is caused by transpiration from the shoot. This demonstrates that transpiration produces a transpiration pull or suction due to transpiration.

PRECAUTIONS:-

1.The leafy shoot should be cut under water and its lower end should be kept dipping in water till fitted into the apparatus.

2.The joint should be air tight.

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