Question

Write a note on the weighing method to check transpiration.

Answer 1

Weighing method is a method to check transpiration in which a small light weight potted plant can be weighed before and after the end of a certain period of time. The soil surface and the pot should be fully covered to prevent evaporation from the surfaces other than the plant. The loss in weight by the plant during that time is due to the loss of water by transpiration.

An improvement in the weighing method can be made by using a glass bottle with a graduated side tube, filled with water and a tube fitted into it. This would indicate the volume of water loss that can be compared with the loss in weight with the help of a weighing machine (B) or by converting cc into grams (1 cc water weighs lg)

Another weighing experiment can be made by using a test–tube filled with water and inserting a leafy shoot (no roots) in it and pouring some oil on the surface to prevent loss of water by evaporation. Rest the test tube in a small beaker and weigh them together. Remove the intact test–tube and keep it straight in the test–tube stand for a few hours. Weigh it again by keeping it in the same beaker. Any difference in weight will indicate loss of water by the shoot (due to transpiration).