Question

What is the purpose of the reservoir in Ganong’s Potometer?

Answer 1

Hint: During transpiration and photosynthesis, the leaves take up moisture. This process of absorption of moisture can be measured. This measurement can be done in a laboratory setting.

Complete answer:
An apparatus with which the absorption of moisture by leaves during transpiration can be measured is known as Ganong’s Potometer. It is also known as a Transpirometer. The measurement is done in a cut twig. In the device, a vertically placed reservoir is attached to the horizontal rod in the apparatus. The water accumulates in the reservoir. And it rests the bubbles and introduces the bubbles formed into the setup. A stop made of pinchcock is placed at the bottom part of the reservoir to regulate the flow of water into the horizontal rod. It can either stop or enable the flow of water.

The reservoir is a funnel and has a tap attached to it. The tap adjusts the flow of water. The rate of transpiration can be measured using two methods: direct and indirect calculations. And the apparatus used coloured water using a dye called eosin for the measurement. And the apparatus is placed over a flat surface where an appropriate amount of sunlight falls on it.

Note: The limitations of Ganong’s Potometer are as follows:
- The forcing of air bubbles within the horizontal rod is time-consuming.
- The process depends on the atmospheric pressure. And minute changes in the pressure changes the position of the air bubble.
- The living time of the newly cut twig will be very less.
- The calculation of transpiration rate would not be accurate and the apparatus can measure only the uptake of moisture.