Question

Explain in your own words with suitable examples. 

Describe the transportation system in plants.

Answer 1

Transportation in plants occurs due to the two processes of root pressure and transpiration. Due to this pressure, food is transported as per the requirement of the plant and this process is transferred through sap vessels. In plants, water and food are transported through the vascular system, for which there are water vessels and sap vessels.

1. Root pressure: Root cells are in contact with water and minerals in the soil. Water and minerals enter the cells on the root surface due to differences in concentration. As a result, these cells become turgid. These turgid cells exert pressure on the adjacent cells. This is called ‘root pressure’. Under the effect of this pressure, water and minerals reach the xylem of the roots and to reduce this difference in concentration they are continuously pushed forward. As a result of this continuous movement, a water column is formed, which is continuously pushed ahead. This pressure is sufficient to lift the water up in shrubs, small plants and small trees.
2. Transpiration pull: Plants give out water in the form of vapour through the stomata on their leaves. Two cells called guard cells are present around the stomata. These cells control the opening and closing of stomata. Transpiration occurs through these stomata. Water is released into the atmosphere by leaves through the process of evaporation. As a result, water level in the epidermal layer of the leaf decreases. Water is brought up to the leaves through the xylem so as to compensate for the lost water. Transpiration helps in absorption of water and minerals and distribution to all parts of the plant whereas root pressure performs the important role of pushing the water up during the night time.