How are water and minerals transported in plants?

Water and minerals are primarily transported in plants through the xylem tissue, which is part of the plant’s vascular system. The movement of water and minerals occurs from the roots, where they are absorbed from the soil, to the other parts of the plant, such as the stems, leaves, and even reproductive structures. This process is known as transpiration and is driven by several factors:

1. Root Uptake:

» Water and minerals are absorbed by the plant’s roots from the soil through a process called osmosis. Root hairs, which are tiny extensions of root epidermal cells, increase the surface area for absorption.

2. Capillary Action:

» Capillary action, or capillarity, helps in the movement of water through the narrow tubes of the xylem. This is due to the cohesive and adhesive properties of water molecules. Cohesion allows water molecules to stick together, and adhesion allows water to adhere to the walls of the xylem vessels.

3. Transpiration:

» Transpiration is the loss of water vapor from the aerial parts of the plant, primarily through small pores called stomata present in the leaves. As water molecules evaporate from the stomata, a negative pressure (tension) is created in the xylem, pulling water from the roots.

4. Root Pressure:

» In some plants, there is a phenomenon known as root pressure, where active transport of minerals into the roots causes water to move into the root xylem. This pressure can force water upward, but it is not the main mechanism for long-distance water transport in most plants.

5. Cohesion-Tension Theory:

» The cohesion-tension theory is the widely accepted explanation for the movement of water in plants. It relies on the cohesion of water molecules and the tension created by transpiration. As water molecules evaporate from the leaves, they create a negative pressure that pulls water upward from the roots. Cohesion between water molecules allows the entire column of water in the xylem to be pulled upward.

The combined effect of root uptake, capillary action, transpiration, and cohesion-tension theory allows for a continuous flow of water and dissolved minerals from the roots to the rest of the plant. This process is crucial for the transport of nutrients, maintenance of turgor pressure, and support of various physiological functions within the plant.