Question

answer the two questions....
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Answer 1

Answer:

Root pressure, in plants, force that helps to drive fluids upward into the water-conducting vessels (xylem). It is primarily generated by osmotic pressure in the cells of the roots and can be demonstrated by exudation of fluid when the stem is cut off just aboveground.

Water is constantly being absorbed by the roots due to the negative water potential in the root cells. This movement of water into the roots can cause the water pressure inside the roots to become high, resulting in a force that 'pushes' water up the stem xylem.

Answer 2

9)

Root pressure can also be called as osmotic pressure that occurs within the cells of a root system. It causes the sap to rise through a plant stem to the leaves. It occurs in the xylem of some vascular plants when the soil moisture level is high.

DEMONSTRATION:

Aim : To demonstrate root pressure.

Material required : A potted plant, knife, rubber tube, glass tube, coloured water.

Procedure: Water the herbaceous plants and keep it for some time. Then cut off the upper part of the stem and attach a narrow glass tube on it. Fill the glass tube with coloured water. Mark the level of water and connect a manometer to the glass tube. Record your observations after some time.

Observations: The colour water rises in level and the manometer shows the root pressure by the increase in mercury level.

Conclusion: The water level increases as a result of root presure. The root pressure is of a small magnitude as shown by the manometer.

10)

• In higher plants, water is absorbed through root hairs from the soil water. The walls of root hairs are permeable to water and are hydrophilic in nature.
• They contain vacuoles filled with cell sap. Absorption of water by roots takes place by two mechanism namely, active absorption and passive absorption.
• During active absorption, the root cells absorb water using metabolic energy released through respi­ration.
• Active absorption could be either osmotic absorption or non-osmotic absorption. In osmotic absorption, water is absorbed from the soil into the xylem of the roots in the osmotic gradient. In non-osmotic absorption, water is absorbed against the osmotic gradient.
• In passive absorption, water absorption is due to transpiration. In this, absorption of water into the root is due to conditions originate in the top of the plant and the root cells play a passive role.
• Osmotic concentration of the root cells is due to the presence of soluble metabolic products synthesized in the aerial parts of the plants and later translocated downwards to the root cells.