NEET BIOLOGY

Detailed explanation-1: -Xylem conducts minerals and water only in the upward direction i.e. from roots towards the stem. Q. Xylem can conduct substances only in one direction, whereas, phloem can transport substances in both directions.

Detailed explanation-2: -The main function of the xylem vessels is to transport water in one direction, upward from the roots, through the stem, and to the leaves. Xylem vessels are very long tubelike structures made of individual cells that are stacked end to end.

Detailed explanation-3: -As transpiration occurs, it deepens the meniscus of water in the leaf, creating negative pressure (also called tension or suction). The tension created by transpiration “pulls” water in the plant xylem, drawing the water upward in much the same way that you draw water upward when you suck on a straw.

Detailed explanation-4: -Unlike in the phloem, where substances can move both up and down the plant, the xylem only transports water and mineral ions up the plant from the roots to the leaves and flowers and any other organs that might require them.

Detailed explanation-5: -There are two main reasons due to which the xylem is unidirectional, namely positive root pressure and transpiration pull. Positive root pressure means it is against the gravitational pull, and the transpiration pull acts as a suction pump for the xylem tube. Thus, the water rises upwards.