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Name phytohormones and write their functions |
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Answer» The plants do not have a nervous system and sense organs like ear ,nose ,mouth,etc like the animals , but they can still sense things.The plants coordinate their behavior against environmental changes by using hormones.The functions of control and coordination in plants is performed by certain chemical substances.These chemical substances are called plant hormones or phytohormones.There are four major types of plant hormones [phytohormones] . which are involved in the\xa0control and coordination in plants.These are :1)Auxins2)Gibberellins3)Cutokinins4)Abcisic acid1)Auxins are the plant hormones which promote cell enlargement and cell\xa0differentiation.\xa0Auxins also promote fruit growth.\xa0Auxin hormone is responsible for phototropic and geotropic responses of plants.2) Gibberellins are plant hormones which\xa0promote cell enlargement and cell\xa0differentiation in the presence of auxins.\xa0Gibberellins help in breaking the dormancy in seeds and buds. They also promote fruit growth.\xa0Gibberellins stimulates elongation of shoots of various plants3) Cytokinins\xa0are plant hormones which promote cell division in plants.They also help in\xa0breaking the dormancy in seeds and buds. The delay the ageing of leaves.Cytokinins promote opening of stomata .4)Abscisic acid (ABA) is a plant hormone which functions mainly as a growth inhibitor.\xa0Abscisic acid promotes the dormancy in seeds and buds [ this is the opposite of breaking the dormancy]. It\xa0also\xa0promotes closing of\xa0stomata. Abscisic acid promotes falling of leaves. Plants need sunlight, water, oxygen, minerals for their growth and development. These are external factors. Apart from these, there are some intrinsic factors that regulate the growth and development of plants. These are called plant hormones or “Phytohormones”.The various functions performed by the plant hormones are:\tAuxins promote cell enlargement and cell differentiadon. They also promote growth.\tGibberellins promote cell enlargement and cell differentiation in the presence of auxin. It also help in breaking the dormancy in seeds and buds. It promote the growth in fruits.\tCytokinins promote cell division and help in breaking the dormancy of seeds and buds. It delay the ageing in leaves. It promotes the opening of stomata and also fruit growth.\tAbscisic acid promotes the dormancy in seeds and buds. It promotes the closing of stomata and falling of leaves. Inhibits growth, reverses the growth promoting effects of auxins and gibberellins. Its effects include wilting of leaves.\tEthylene promotes the falling of leaves, ripening of fruits and helps in breaking bud dormancy. |
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