Question

Potometer works on the principle of –
A. Potential difference between the tip of the tube and that of the plant
B. Amount of water absorbed equals to the amount of transpired
C. Osmotic pressure
D. Root pressure

Answer 1

Photometer is an instrument or we can say an apparatus which is used to measure the water intake. Amount of water intake is directly proportional to the rate of transpiration. Transpiration is a process of evaporation of water in the form of vapours from the aerial part of the plant body. Rate of transpiration is affected by temperature, air, humidity and light intensity.

Complete answer:
The Potometer is discovered by Boss. Potometer is made up of glass and consists of a long tube which is bent at the right angles.
How it works : Potometer measures the rate of water intake from a plant. It is almost impossible to measure the accurate transpiration so we consider water uptake to indicate the rate of transpiration. As it is already proved that water uptake is directly proportional to the rate of transpiration. Take a sample of a plant which must be cut from a plant which is underwater. This has to be done to prevent air being entered in xylem and to break the water column. Potometer is filled with water and all the air bubbles are removed. The sample plant is then attached to the potometer by using rubber seal or petroleum jelly. One air bubble is added to equipment. Here the transpiration pull is created, making the bubble to move. The distance that it takes to move toward the plant is recorded. This is how it works. The principle on which a potometer works is that the amount of water absorbed is equal to the amount of water transpired.

So the correct answer is B amount of water absorbed is equal to the amount of water transpired.

Note: The rate of transpiration is calculated as amount of water loss. Water losses through the stomata on the leaf. In order to arrive at the rate of transpiration it is necessary to calculate the surface area of the leaf. As mostly stomata are present at the lower epidermis so we need to calculate that surface area.