We know from a very early age that plants obtain water through their roots, though it is not perhaps until our
school biology lessons that we learn of the important role that water plays in the process of photosynthesis. Most of the water absorption is carried out by the younger part of the roots. Just behind the growing tip of a young root is the piliferous region, made up of hundreds of projections of the epidermal tissue, the root hairs.
- STRUCTURE INVOLVED IN WATER ABSORPTION
In higher plants water is absorbed through root hairs which are in contact with soil water and form a root hair zone a little behind the root tips. Root hairs are tubular hair like prolongations of the cells of the epidermal layer (when epidermis bears root hairs it is also known as pilloferous layer of the roots. - The walls of root hairs are permeable and consist of pectic substances and cellulose which are strongly hydrophilic in nature root hairs contain vacuoles filled with cell sap. When roots elongate, the older root hairs die and new root hairs are developed so that they are in contact with fresh supplies of water in the soil. Lateral Movement of water is achieved through root. This can described as follows:
ROOTS
- Often roots are overlooked, probably because they are less visible than the rest of the plant. However, it’s
important to understand plant root systems because they have a pronounced effect on a plant’s size and
vigor, method of propagation, adaptation to soil types, and response to cultural practices and irrigation. - Roots typically originate from the lower portion of a plant or cutting. They have a root cap, but lack nodes and never bear leaves or flowers directly. Their principal functions are to absorb nutrients and moisture, anchor the plant in the soil, support the stem, and store food. In some plants, they can be used for propagation.
STRUCTURE OF ROOTS
- The meristem is at the tip and manufactures new cells; it is an area of cell division and growth.
- Behind the meristem is the zone of elongation. In this area, cells increase in size through food and water
absorption. As they grow, they push the root through the soil. - The zone of maturation is directly beneath the stem. Here, cells become specific tissues such as
epidermis, cortex, or vascular tissue. - A root’s epidermis is its outermost layer of cells. These cells are responsible for absorbing water and
minerals dissolved in water. Cortex cells are involved in moving water from the epidermis to the vascular tissue (xylem and phloem) and in storing food. Vascular tissue is located in the center of the root and conducts food and water.
- Externally, there are two areas of importance: the root cap and the root hairs. The root cap is the root’s outermost tip. It consists of cells that are sloughed off as the root grows through the soil. Its function is to protect the root meristem.
- Root hairs are delicate, elongated epidermal cells that occur in a small zone just behind the root’s growing tip. They generally appear as fine down to the naked eye. Their function is to increase the root’s surface area and absorptive capacity. Root hairs usually live 1 or 2 days. When a plant is transplanted, they are easily torn off or may dry out in the sun.
