Question

Force developed in the cortex of root, which pushes water into the xylem of root from soil:
(A) Diffusion
(B) Osmotic pressure
(C) Turgor pressure
(D) Root pressure

Answer 1

Hint: The above pressure is related to water transport in the plant. The plant is related to water in a way that the plants control the hydration of their cell, including the collection of water from the soil, its transport within the plants, and its loss by the evaporation from the leaves.

Complete answer: Root pressure is the transverse osmotic pressure within the cells of a root system that causes sap to rise through a plant stem to the leaves. Root pressure is studied by removing the shoot of a plant near the soil level. It is caused by the distribution of mineral nutrient ions into the root xylem. Root pressure is caused by the accumulation of water in the xylem pushing on the rigid cells.
Root pressure is positive. The different ions from the soil are actively transported into the vascular tissues of the root. It is primarily generated by osmotic pressure in the cells of the roots and can be demonstrated by the exudation of fluid when the stem is cut off just above the ground. The root pressure is partially responsible for the rise of water in vascular plants. It explains guttation in some plants and this is also a possible factor that explains transpiration streams in plants where water rises against gravity to move to areas that have less amount of water. The exudation of water is also caused by the root pressure. Diffusion is the process in which the movement of a substance from an area of high concentration to an area of low concentration. Turgor pressure(TP) is the pressure exerted by protoplasm on the wall and wall pressure(WP) is the pressure exerted by the wall on to the protoplasm.
Hence, the correct answer is option (D), i.e., Root pressure.

Note: Priestley has put forward the theory of root pressure. It is a positive pressure that develops in the xylem sap of the root of some plants. The root pressure is partially responsible for the rise of water in vascular plants.