Name phytohormones and write their functions

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 control and coordination  in plants.These are : 1)Auxins 2)Gibberellins 3)Cutokinins 4)Abcisic acid 1)Auxins are the plant hormones which promote cell enlargement and cell differentiation. Auxins also promote fruit growth. Auxin hormone is responsible for phototropic and geotropic responses of plants. 2) Gibberellins are plant hormones which promote cell enlargement and cell differentiation in the presence of auxins. Gibberellins help in breaking the dormancy in seeds and buds. They  also promote fruit growth. Gibberellins stimulates elongation of shoots of various plants 3) Cytokinins are plant hormones which promote cell division in plants.They also help in breaking 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. Abscisic acid promotes the dormancy in seeds and buds [ this is the opposite of breaking the dormancy]. It also promotes closing of stomata. 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:

1. Auxins promote cell enlargement and cell differentiadon. They also promote growth.
2. Gibberellins 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.
3. Cytokinins 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.
4. Abscisic 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.
5. Ethylene promotes the falling of leaves, ripening of fruits and helps in breaking bud dormancy.