How do cohesion and adhesion help plants transport water?

Cohesion and adhesion are two important properties of water that play a crucial role in the transport of water within plants, a process known as capillary action. These properties contribute to the movement of water from the roots to the leaves through a complex network of cells called xylem vessels. Here's how cohesion and adhesion work together to facilitate water transport in plants:

Cohesion: Cohesion refers to the attraction between water molecules due to their hydrogen bonding. Water molecules tend to stick together, creating a continuous column of water. This property is especially strong in narrow tubes like the xylem vessels found in plants. As water evaporates from the leaves through tiny pores called stomata in a process called transpiration, it creates a negative pressure or tension in the xylem vessels. This tension pulls water upwards from the roots.

Adhesion: Adhesion refers to the attraction between water molecules and the walls of the xylem vessels. Water molecules are attracted to the hydrophilic (water-attracting) surfaces of the vessel walls. This adhesion counteracts the force of gravity and helps water to "stick" to the sides of the vessels. Adhesion, along with cohesion, helps prevent the water column from breaking under the tension created by transpiration.

The combined effects of cohesion and adhesion create a continuous pathway for water movement from the roots to the leaves. As water is pulled up through the xylem vessels due to transpiration, the cohesive forces between water molecules ensure that a continuous column of water is maintained. Adhesion ensures that water adheres to the xylem vessel walls, helping to counteract the force of gravity and preventing the water column from collapsing.

It's worth noting that this process is often referred to as the cohesion-tension theory, and it's a crucial mechanism for the transport of water and nutrients in plants. This mechanism enables plants to maintain their water balance, support their structure, and facilitate the movement of nutrients from the soil to various parts of the plant.