Question

Describe the methods to measure transpiration in plants.

Answer 1

The two primary methods used to measure the rate of transpiration in plants are the weighing method and the potometer method. In the weighing method, a small potted plant is weighed at the start and end of a set period, making sure that the soil surface is tightly covered with an impermeable sheet to prevent any direct evaporation from the soil. The total decrease in the weight of the pot during this time indicates the exact amount of water lost through transpiration. In the potometer method, a device like Ganong's potometer is utilized to measure the rate of water absorption by a freshly cut leafy shoot. Because the volume of water taken up by the plant is nearly equal to the volume of water vapor released, measuring the speed at which an air bubble moves across a graduated capillary tube gives a quantitative measurement of transpiration.