Question

Explain the experiment of Ganong's potometer.

Answer 1

Ganong's potometer is an apparatus used to measure the rate of water intake by a plant shoot during transpiration. To set up the experiment, a fresh, leafy shoot is cut under water to avoid any air bubbles entering the xylem vessels, and it is tightly fixed into the mouth of the potometer jar. The entire apparatus is filled completely with water, ensuring no air bubbles are trapped inside. A single air bubble is then introduced into the horizontal graduated capillary tube by dipping its outer end in water and lifting it momentarily. As the leafy shoot transpires, it creates a transpiration pull that sucks water upward from the apparatus, causing the introduced air bubble to move along the graduated scale. By recording the distance traveled by the air bubble in a specific time interval, the rate of water absorption (and thus the approximate rate of transpiration) can be calculated.