Phytohormoes similarities and antagonistic in all aspect?
In plants, growth, development, and response to the environment is controlled and coordinated by a special class of chemical substances known as phytohormones. There are five major types of phytohormones: auxins, gibberellins, cytokinins, abscisic acid, and ethylene. These phytohormones are either growth promoters such as auxins, gibberellins, cytokinins, and ethylene, or growth inhibitors such as abscisic acid.
When the growing parts of a phototropic plant detect sunlight, auxins (synthesized at the shoot tips) help the cells grow longer. When light falls on one side of the plant, the auxins generally diffuse towards the shaded side of the shoot. This stimulates the cells in the shaded area to grow longer than the corresponding cells of the illuminated region. This results in the curvature of the plant stem tip towards the light.
They are produced in the roots of a plant. They promote stem elongation by promoting cell division in the inter-nodal region.
They promote cell division. Therefore, they are present in greater concentration in those areas of the plants where rapid cell division occurs. For example, tip of the shoot.
- Abscisic acid
It promotes seed dormancy by inhibiting cell growth. It is involved in the opening and closing of stomata. It is also responsible for the shedding of leaves.
It is a gaseous plant hormone. It regulates fruit ripening. It is produced during the ripening of fruits.
|Hormone name||Precursor (made from)||Site of production|
|Cytokinin||Adenine derivative||Shoot and root tips|
|GA||Isoprenoid derived/pathway||Internodal region|
|ABA||Mevalonic acid derived||Synthesized in plastids|
|Ethylene||Methionine||Produced at ripening|
* More details of these hormones along with other phytohormones such as NO (Nitrc oxide, Brassinosteroids, Jasmonic acid, Salicylic acid). You will learn them in your subsequent higher classes.
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