Question

Which of the following is responsible for passive guttation?
(a) Tension-cohesion of water molecules.
(b) Activity of epithem tissue.
(c) Root pressure.
(d) Secretion of fluid by mesophyll cells.

Answer 1

This is a force that helps to drive fluids upward into the xylem vessels. Primarily it is generated by osmotic pressure in the cells of the roots. It can be demonstrated by showing the flow of fluid when the stem is cut off just above the ground.

Complete answer:
Root pressure is responsible for passive guttation. Guttation is caused due to root pressure and also it causes permanent loss of water. It is not dew. Dew is fluid that condenses onto the plant surface from the atmosphere.
-Guttation is mainly the loss of water in the form of water droplets from hydathodes present on the leaf margin of the small herbaceous plants.
-Guttation can also be explained as the process of secretion of drops of xylem sap from hydathodes on the tips or edges of leaves of some vascular plants, such as grasses, and several fungi. It generally happens at night and early morning.
-In rare cases, during guttation bacteria can grow on droplets and may be pulled back to the leaf when the sun comes up, resulting in disease infection.
-Plants release the excess absorbed water by guttation and transpiration so, in this way, it cools the plant and the surrounding atmosphere as well. When the surrounding atmosphere becomes hot, this cooling takes place.

Note:
-Hydathodes are a kind of pore that secrete water and are present on leaf margins. They are commonly found in angiosperms.
-It is an important process by which removal of extra water from plants is done and in this way plants balance the amount of water they absorb.
-In the condition when the soil moisture level is high either at night or during the daytime when transpiration is low there occurs a process in the xylem tissues of some vascular plants this process is known as root pressure.