Question

Purpose of air bubble in a potometer

Answer 1

The introduction of bubble in photometer shows that some water is lost through transpiration by leaf and thus water is taken in by it.
As, water taken = water lost, we come to know the amount of water lost through transpiration


Hope it helps

Answer 2

Question:

How can transpiration be measured by weighing?

Answer:

Weighing method is used for measurement of transpiration. A small lightweight potted plant can be weighed before and after the end of a certain period of time. ... The loss in weight by the plant during that time is due to the loss of water by transpiration.