EXPERIMENT 6 Objective. To compare the rate of transpiration from the upper and lower surfaces of the leaf.

                               EXPERIMENT 6

Objective. To compare the rate of transpiration from the upper and lower surfaces of the leaf.

REQUIREMENTS

A potted plant, filter paper, 3% cobalt chloride solution, glass slides, clips, desiccator, stop watch, punching machine etc.

PROCEDURE

1.Prepare cobalt chloride paper by dipping a filter paper in a 3% cobalt chloride solution. Dry the filter paper and cut discs of suitable size with the help of punching machine. Store these discs in a desiccator. The filter paper is pink in colour when wet but become blue on drying.

2.Place the dried discs of cobalt chloride paper, one each on the upper and lower surfaces of a leaf of the potted plant. Press them close to surfaces of glass slides. Clip the slides together.

3.Note the time taken by the cobalt chloride paper to change its blue colour to pink.

OBSERVATION

The time taken for change in colour of the cobalt chloride paper from blue to pink on the lower leaf surface is less than the upper surface.

CONCLUSION

The quick change in the colour of cobalt chloride paper on the lower surface indicates higher rate of loss of water vapour from this surface than the upper one. This is due to more stomata per unit area on the lower surface than the upper one.

PRECAUTIONS

1. Always take a well waterd potted plant for the experiment.

2.Always handle the dried cobalt chloride paper with dry hands or forceps.

3. The leaf surface should not be wet while putting the cobalt.