Name: Transport Mechanism in Plants
Uploaded: 2019-07-19
Duration: 5 min
Description: Plants contain a vast network of conduits which consist of the xylem and phloem. This is more like the circulatory system. Learn more.

Question

What is significance of transpiration? Explain root pressure theory and its limitations.

Accepted Answer

Significance of Transpiration:

This process is significant as:

It gives a cooling effect to the plants.

It removes excess water absorbed by the roots.

It helps in ascent of sap through the xylem due to the creation of DPD and transpiration pull.

It maintains turgor pressure of the cells.

It helps in the passive absorption of water and minerals from soil by the roots.

Root pressure:

The physiological activities of the root cells are suggested to be responsible for the ascent of sap. It is shown that when a herbaceous potted plant is cut by a sharp knife above the ground, xylem sap comes out. This proves the presence of root pressure. Root pressure is a positive hydrostatic pressure developed in the living cortical cells of the roots. Due to root pressure ascent of sap take place in the plants. The value of root pressure is +1 to +2 bars which is enough to pump water to a height of 10 to 20 meters.

However:

Root pressure value is almost nearly zero in taller gymnosperm trees.

Plant which has excessive transpiration rate will have negative root pressure.

What is significance of transpiration? Explain root pressure theory and its limitations.

Important Questions on Plant Water Relation

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