What is the function of plant roots?

Plant roots, as the name suggests, are the roots of plants. They refer to the part of the plant underground. Most plants have roots. The role of plant roots is also very important. They can not only fix their position but also provide nutrients to the plants, allowing them to grow better.

Absorbs water and inorganic salts

The most active part of the root system that absorbs water from the soil is the root hair area at the root tip. The water absorption phenomenon usually caused only by root activity is called active water absorption, while the water absorption process caused by transpiration of the above-ground part is called passive water absorption. The absorption of minerals by roots from the soil is an active physiological process, which is relatively independent of the absorption of water. The most active areas of roots absorbing mineral elements are the root cap and apical meristem, as well as the root hair development zone. Various ions in the soil are first adsorbed on the root surface, and then enter the cells through the cell membrane through energy conversion and action, and then enter the xylem vessels of the vascular column through ion exchange between cells.

The absorption function of the root system: One is the active "interception" of soil nutrients by the roots. The second is that under the influence of plant growth and metabolic activities (such as transpiration and absorption), nutrients in the soil migrate to the root epidermis, which becomes "mass flow and diffusion".

"Intercepted" nutrients are absorbed directly from the soil that the new roots come into contact with as the roots continue to grow.

"Mass flow" is the process in which the water potential at the root zone decreases due to plant transpiration, and the nutrients dissolved in the soil migrate to the root surface of the plant along with the soil water.

"Diffusion" refers to the process by which nutrients migrate to the root surface by diffusion (free flow), which is slow and short distance.

Fixation and support

The root system firmly anchors the above-ground parts of the plant to the soil.

Synthesis ability

The roots can carry out the synthesis and transformation of a series of organic compounds. These include amino acids that make up proteins, such as glutamic acid, aspartic acid and proline; various plant hormones, such as arginine, acetate, cytokinins, and a small amount of ethylene.

Storage function

The root parenchyma is well developed and serves as a place for storing substances.

Conduction function

The conduction function is performed by the area above the root apex. The water and inorganic salts absorbed by the root hairs and epidermal cells are transported to the stems and leaves through the vascular tissue of the roots. The organic matter produced by the leaves is also sent to the roots through the stems and transported to various parts of the roots by the vascular tissue of the roots, maintaining the growth and life of the roots.

Mycorrhizae and nodules

The roots of many plants establish a symbiotic relationship with microorganisms in the soil, forming mycorrhizae or nodules on the plants. The symbiosis formed by the roots of some seed plants and soil fungi is called mycorrhiza. According to the infection of the host cortical cells by the fungi, it can be divided into two types: ectomycorrhiza, in which the fungi form a sheath, i.e. the hyphae cover, which completely wraps the outside of the young root, and only a few hyphae invade the cell gaps of the root cortex, such as pine and oak trees. In endomycorrhizae, the fungi form an inconspicuous cover, while most of the hyphae invade the cells of the root cortex, such as orchids and strawberries. The hyphae of mycorrhizal fungi act like root hairs, absorbing water and mineral nutrients. It can also convert mineral salts and organic matter in the soil into nutrients that are easily absorbed by the host, and produce vitamins to supply the root system. The sugars, amino acids and other organic substances secreted by the host plant can provide fungi with living materials, so the two have a symbiotic relationship. The symbiosis between leguminous plants and root nodule bacteria is called nodule. The vascular bundles of the nodules are connected to the vascular columns of the roots, and the two can exchange nutrients. On the one hand, the legumes supply water and nutrients to the growth of nodule bacteria; on the other hand, the nodule bacteria also transport the fixed synthesized ammonium nitrogen to the host plant through the conducting tissues.