Question

Guttation is a result of
A. Diffusion
B. Transpiration
C. Osmosis
D. Root pressure

Answer 1

Hint: The soil is moist at night. The rate of transpiration is low at that time. So the release of water is by means other than transpiration.

Complete step by step solution:
Starting with the definition- what guttation means? Guttation is the exudation from the xylem sap in some vascular plants, such as grass, in the form of drops. This usually happens at night. During the day, the excess water present in the plant or root is exudated from the plant through transpiration. But at night when the transpiration rate is low, guttation helps to release the excessive water. Now let us see which out of the four options can be the cause of guttation.

> Option A- Diffusion: Diffusion is simply the movement of molecules from higher concentration to the lower concentration. During the day, the concentration of oxygen and water is high in leaves so they move out by the transpiration.
> Option b- Transpiration: Transpiration is the loss of water from the plants. At night, stomata are partially open to conduct the transpiration process but the rate is very low to remove the excess water in the form of drops on the leaves.
> Option c – Osmosis: osmosis is the diffusion of water from a dilute to a more concentrated medium through a semipermeable membrane.
> Option D - Root pressure: It is the transverse osmotic pressure which is created in the root system when the soil is very moist. This will cause the sap to move towards the leaves. At night as the transpiration rate is low, there is no transpirational pull so the excessive water is exudated just by the guttation process under the root pressure.

So our answer is the option D- Root pressure.

Note: Drops by guttation are not to be confused by the dew in the morning. Dew is condensed water from the atmosphere on the leaf surface whereas guttation drops are oozing of water drops from the unwounded edges of the leaves.