What is the role of lignin in xylem vessels?

Lignin in xylem vessels provides structural support and helps in water conduction.

Lignin is a complex organic polymer that is deposited in the cell walls of xylem vessels, contributing to their rigidity and strength. This structural support is crucial for the plant's upright growth and resistance against various environmental stresses. The presence of lignin makes the xylem vessels hard and woody, enabling them to withstand the negative pressures created during the process of water transport.

Moreover, lignin plays a significant role in water conduction. It is hydrophobic, meaning it repels water, which aids in the efficient movement of water and dissolved minerals from the roots to the rest of the plant. This hydrophobic property of lignin prevents water from seeping out of the xylem vessels, ensuring that the water column remains unbroken and continuous. This is particularly important in tall plants and trees, where water needs to be transported to great heights against the force of gravity.

In addition, lignin in xylem vessels also serves as a barrier against pathogens. Its complex, irregular structure makes it difficult for most organisms to degrade, thus providing a form of defence against microbial attacks. This protective function is particularly important in the xylem, which, due to its role in water transport, could otherwise provide an easy route for the spread of pathogens throughout the plant.

In summary, lignin in xylem vessels plays a multifaceted role. It provides structural support, aids in water conduction, and offers protection against pathogens. Its presence is vital for the survival and growth of plants, particularly those that need to transport water to great heights.