NEET BIOLOGY

Detailed explanation-1: -Cohesion and adhesion work together to pull water molecules from the roots, through xylem vessels of the stem, and out of the plant through the stomata on the leaf. This is often referred to as the cohesion–adhesion, or cohesion–tension theory of water transport.

Detailed explanation-2: -The cohesion-tension theory (C-T theory) by Boehm (1893) and Dixon and Joly (1894) postulates that the water ascent in trees is exclusively due to the transpirational pull from continuous water columns in the xylem conduit running from the roots to the leafs.

Detailed explanation-3: -Cohesion-When two similar substances or molecules experience the force of attraction then this force is known as the cohesion force. Adhesion-When two dissimilar substances or molecules experience the force of attraction then this force is known as the adhesion force.

Detailed explanation-4: -The cohesion – tension theory of sap ascent explains how how water is pulled up from the roots to the top of the plant. Evaporation from mesophyll cells in the leaves produces a negative water potential gradient that causes water and minerals to move upwards from the roots through the xylem.

Detailed explanation-5: -According to the cohesion-tension theory, transpiration is the main driver of water movement in the xylem. It creates negative pressure (tension) equivalent to –2 MPa at the leaf surface. Water from the roots is ultimately pulled up by this tension.