Question

How is water taken up by roots and transported throughout a plant? What are the pathways and mechanisms used?

Answer 1

Ans.

Water is taken up by roots and transported throughout a plant in the following way:

• Water that is found in spaces between the soil particles enters through wall and cell membranes of the root hair cell by the process of osmosis.Root hairs have thin walls that speeds up the intake of water by osmosis and the large vacuoles it contains absorbs the water quickly and transport it to the next cell.
• Some of the water molecules moves across the parenchyma cells of the cortex through osmosis,while most of the other water molecules travels in the between the parenchyma cell walls by simple diffusion.
• Water passes through the endodermis and enters the xylem.
• Now, water in the xylem is drawn up the stem through transpiration.Due to transpiration there is a constant water loss from the leaves,causing a negative pressure in the leaves.This negative pressure works like a suction force and pulls the water up the stem.
• Now water travels to the leaves via stem through three processes; transpiration,capillary action and root pressure.Like in the previous step,the negative pressure due to transpiration pull the water up the stem and this creates a capillary action to which the stem xylem is structurally adapted,promoting more uptake of water through stem.The third force,root pressure caused by the constant absorption of water by the roots results in the pressure of water inside roots to increase and thus creating a force that pushes the water up the stem xylem.
• Water now moves along the xylem into the leaf where it gets evaporated into air spaces in spongy mesophyll.
• When leaves transpires the water vapor escapes through the stomata.