NEET BIOLOGY

Detailed explanation-1: -Transpiration is ultimately the main driver of water movement in xylem. The cohesion-tension model works like this: Transpiration (evaporation) occurs because stomata are open to allow gas exchange for photosynthesis.

Detailed explanation-2: -Stomata are open to let carbon dioxide in for photosynthesis; however, this also causes the water in the mesophyll tissue in leaves to evaporate if the air outside is drier due to factors like high temperature.

Detailed explanation-3: -1-Water is passively transported into the roots and then into the xylem. 2-The forces of cohesion and adhesion cause the water molecules to form a column in the xylem. 3-Water moves from the xylem into the mesophyll cells, evaporates from their surfaces and leaves the plant by diffusion through the stomata.

Detailed explanation-4: -The regulation of water flow through xylem depends on many different factors. The main factor is the evaporation of water from the leaves, which creates a missing gradient in the leaves. This exerts a negative pressure from The roots which will pull water into the roots and up through the xylem back up to the leaves.

Detailed explanation-5: -Once water is in the xylem, it travels upwards-against the force of gravity-towards the rest of the plant. Water is able to move against gravity due to two forces: tension and cohesion. Tension is a ‘sucking force’ which is created when water evaporates from leaves (transpiration), pulling more water into the leaf.