The movement of water from the soil into plant roots and subsequently into the upper portions of the plant is a vital process known as water uptake and transport in plants. This process primarily involves two mechanisms: absorption by roots and transport through the plant’s vascular system.

1. Absorption by Roots: Plant roots have specialized structures called root hairs, which increase the surface area for water absorption. These root hairs are in close contact with the soil particles. The process of water uptake by roots occurs as follows: a. Root Pressure: The root cells actively transport mineral ions from the soil into their cytoplasm, creating a concentration gradient. This leads to the accumulation of solutes in the root cells, increasing the osmotic potential. b. Osmosis: Due to the higher solute concentration in the root cells, water from the soil moves into the root cells by osmosis. This creates a water potential gradient, with water moving from an area of lower solute concentration (soil) to an area of higher solute concentration (root cells).
2. Transport through the Vascular System: Once water is absorbed by the root cells, it moves upward through the plant via two types of vascular tissues: xylem and phloem. a. Xylem Transport: The primary pathway for water movement is the xylem, a specialized tissue that transports water and minerals from the roots to the upper parts of the plant. Water is pulled upward through the xylem due to transpiration, which is the loss of water vapor from the leaves through stomata. As water evaporates from the leaves, it creates a negative pressure gradient, known as tension, which pulls water up from the roots. b. Cohesion-Tension Theory: According to the cohesion-tension theory, water molecules are cohesive (stick together) due to hydrogen bonding. As water evaporates from the leaves, it pulls on the adjacent water molecules, creating a continuous column of water from the roots to the leaves. This cohesion, combined with the tension generated by transpiration, enables the upward movement of water in the xylem.
3. Water Distribution in the Plant: Once water reaches the leaves, it is used for various plant processes such as photosynthesis and cell expansion. Water molecules are continually evaporating from the leaf surfaces through stomata, creating a constant flow of water from the roots to the leaves. This process is called transpiration.

In summary, water is absorbed by the roots through osmosis, driven by the higher solute concentration in the root cells. The water then moves upward through the plant’s xylem tissue, primarily due to transpiration and the cohesive properties of water. This allows for the distribution of water and minerals to the upper portions of the plant, ensuring its growth, metabolism, and overall functioning.