The hygroscopic water is held by colloidal soil particles, due to cohesive forces, and is absorbed by plants in a very small quantity Usually, water absorption occurs in plants through roots, which are often extensive and grow rapidly in the soil. The zone of rapid absorption is characterized by the presence of root hairs.
Root hairs develop mainly at the tip, just above the zone of elongation.
Root hairs are thin-walled slender extensions of root epidermal cells that
increase the surface area of root and help in absorption of water from the soil. A root hair is generally delicate and short lived. The cell wall of root hair is composed of two distinct layers
Cytoplasm.
The outer layer, which is composed of pectic substances, helps
Vacuole filled with cell sap to adhere soil particles.
The inner layer is made up of cellulose.
Structure of a single root hair cell wall of the root hair is permeable to both solute and solvent molecules. It surrounds the plasma membrane.
Each root hair has a central vacuole illed with osmotically active cell sap and a peripheral cytoplasm. For long distande
transport, plants have developed a mass or bulk flow system which operates through development of pressure
differences between the source and sink.
In mass or bulk flow, all the substances dissolved or suspended in solution travel at the same pace. Long distance bulk
movement of substances thatoccurs through conducting or vascular tissues of plants is called translocation scular tissues, xylem and phloem. Xylem translocation is mainly from roots to aerial parts. It passes me organic nitrogen and hormones. Phloem translocates organic substances and inorganic
ns. Storage organs re-export organic nutrients There are two va solutes, first from leaves to all other parts of the plant and storage orga to those parts which require the same, as newly formed leaves and fruits Translocation operates either due to positive hydrostatic pressure gradient, as in phioem pressure gradient as in xylem or a negative hydrostati
Pressure gradient as in xylem.
