Growth and development of some plants are regulated by the activity of plant hormones. Hormones are the biochemical substances that are produced in one part of a plant and are moved to a different part where they exert a particular effect. Examples of a plant hormone are substance known as auxins (group of plant growth regulating substances or hormones).
The length of most plant cells are increase by auxins and thereby contribute to the growth and elongation of the plant.
Another plant hormone is the abscisic acid (hormone that inhabits growth), which is produced in mature leaves and inhibits growth in developing leaves and germinating seeds, Ethylene (colourless gaseous unsaturated hydrocarbon) is also a plant hormone which encourages ripening and the dropping of leaves and fruits from the trees. Slight pressure permits the fruit to break loose from the stem.
The two important growth regulating hormones are the gibberellins (acids of complex nature) and the cytokinins. Gibberellins affect plants by the stimulating of their growth through rapid stem elongation. Cytokinins induces the plant cells to undergo mitosis, therefore, they encourage increased growth in the roots and stems of plants. They also promote flowering and stimulation of some seeds to enhance germination.
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| Plant Hormones |
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