How do xylem cells transport water?

Xylem cells transport water through a process called transpiration, which involves the movement of water from roots to leaves.

Xylem cells are specialised cells found in plants, primarily responsible for the transportation of water and nutrients from the roots to the rest of the plant. This process is known as transpiration. The xylem cells form long, continuous tubes that run from the roots, through the stem, and into the leaves.

Transpiration begins in the roots, where water is absorbed from the soil. This water then moves into the xylem cells, where it begins its journey upwards. The driving force behind this upward movement is the evaporation of water from the leaves, also known as transpiration. As water evaporates from the leaves, it creates a kind of suction that pulls more water up through the xylem cells.

The structure of the xylem cells themselves also aids in this process. They are long and narrow, which helps to create a capillary action. This is a phenomenon where liquid spontaneously rises in a narrow space due to the forces of cohesion (attraction between similar molecules) and adhesion (attraction between different molecules). In the case of the xylem, the water molecules (cohesion) stick to the cellulose in the xylem cell walls (adhesion), and also to each other, helping to pull the water column upwards.

Furthermore, the walls of the xylem cells are thickened with a substance called lignin. This makes them strong and prevents them from collapsing under the pressure of the transpiration pull. It also ensures that the cells are waterproof, so water can't escape from the sides of the xylem tubes.

In summary, xylem cells transport water through a combination of transpiration, capillary action, and the physical properties of their structure. This process is vital for the survival of the plant, as it allows water and nutrients to reach all parts, from the roots to the leaves.