How do plants transport water and nutrients?
The Correct Answer and Explanation is :
Plants transport water and nutrients through specialized vascular tissues: the xylem and phloem. The xylem is responsible for moving water and dissolved minerals from the roots to the leaves, while the phloem distributes the products of photosynthesis, primarily sugars, from the leaves to other parts of the plant.
Water and Nutrient Transport via Xylem:
Water absorption begins in the roots, where root hairs increase surface area to efficiently take up water and minerals from the soil. This water enters the xylem vessels, which are hollow tubes formed by dead, lignified cells. The movement of water through the xylem is driven by a combination of capillary action, root pressure, and the cohesion-tension mechanism.
The cohesion-tension theory explains that as water evaporates from the leaves through small openings called stomata—a process known as transpiration—it creates a negative pressure that pulls more water upward from the roots through the xylem. This continuous column of water is maintained due to the cohesive properties of water molecules, which stick together, and the adhesive properties, which allow them to stick to the walls of the xylem vessels. This mechanism efficiently transports water and dissolved minerals to all parts of the plant. citeturn0search13
Nutrient Transport via Phloem:
The phloem consists of living cells that transport the products of photosynthesis, primarily sugars, from the leaves (the source) to other parts of the plant (the sinks), such as roots, stems, and fruits. This movement occurs through a process called translocation, which relies on a pressure-flow mechanism.
In the source leaves, sugars are actively loaded into the phloem sieve tubes, increasing the osmotic pressure and drawing water into the phloem from the surrounding tissues. This influx of water creates a high-pressure area that pushes the phloem sap toward the sinks, where sugars are actively unloaded and utilized or stored. The pressure difference between the source and sink regions drives the flow of nutrients throughout the plant. citeturn0search0
In summary, plants utilize the xylem and phloem to transport water, minerals, and nutrients efficiently. The xylem relies on physical forces like capillary action and transpiration to move water upward, while the phloem uses osmotic pressure gradients to distribute sugars and other nutrients to various parts of the plant.