Explain roots, stems and leaves in plants.

Essay by head141High School, 12th grade January 2003

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Primary Growth of Roots: Growth in Length

A major part of the root is the root cap; the root cap is the covering on the end that protects the growing root. Cells in the root cap are aware of the direction of gravity and direct the root growth accordingly. As the root grows the outer cells of the root cap gradually get scraped off, as to be expected when growing in the rough soil particles. Another function of the root cap is to support the apical meristem. The apical meristem is the site where cells divide and produce new cells for both the root and root cap. Above the apical meristem is the zone of elongation. In the zone of elongation cells divide more slowly and grow long pushing the root cap and apical meristem through the soil. Above the zone of elongation is the zone of maturation. As the name might suggest, cells have reached their full size and they develop into specialized cells.

Primary Structure of Roots

The structure of roots is made up of primary tissues, the epidermis, root hairs, the cortex, the endodermis and the pericycle. Primary tissues are formed from cells laid down by the apical meristem's activity. The epidermis is the outermost layer; it's one cell thick and it's located around the root. Root hairs are extensions that grow out among the soil particles. The function of the root hairs is to anchor the plant into the soil and d increase surface area to absorb water and minerals. The cortex is most of the root's main tissue; it's a thick layer of ground tissue just inside the epidermis. The cortex is made up of parenchyma cells which contain amyloplasts that store starch. The endodermis is a single layer of cells at the inner...