Question

Which of the following is used to determine the rate of transpiration in plants?
A. Porometer
B. Potometer
C. Auxanometer
D. Tensiometer

Answer 1

Hint: Transpiration is defined as the loss of the water in the form of vapor from the aerial parts of the plant. It is said to be a necessary unavoidable and evil process. Transpiration occurs via cuticles, lenticels, bark, and stomata in the plants.

Complete answer: -Porometer: A porometer is a device that is used to measure the degree of the stomatal opening by measuring the area of the opening of the stomata on the leaves. The porometer measures the quantity of the gas that passes through the stomata and based on that it estimates the area.
-Potometer: It is also known as the transpirometer. A potometer is a device that is used to measure the rate of transpiration in plants. The potometer measures the rate of the uptake of the water by the leaves and the shoot of the plants which is equal to the amount of the water that is lost by the plant via transpiration. This is because the causes of water uptake in a plant are primarily transpiration and photosynthesis.
-Auxanometer: The auxanometer is a device which is used to measure the rate of growth in plants, in terms of the increase in the length of the plant or elongation. Commonly an arc auxanometer is used to measure the increase in the length of the plant w.r.t time.
-Tensiometer: A tensiometer is a device which is to measure the water potential of a solution or any cell. It measures the soil moisture tension in the vadose zone. Thus, based on the above information we can conclude that the rate of transpiration in plants is determined with the help of a Potometer.
Hence, the correct answer is option (B).

Note: Potometers are of two main types. These two types are the bubble potometer and the mass potometer. As the name suggests, in a bubble potometer, a small air bubble is introduced into a capillary tube. As the plant takes in the water, the bubble moves in the capillary tube. Therefore, by calibrating the capillary tube, the water uptake can be determined. On the other hand, in a mass potometer, the roots of a plant are submerged in a beaker that is placed on a digital balance. Readings are taken to measure the amount of water that is lost by the plant.