Question

what is plant hormones ? ​

Answer 1

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The control and coordination in plants is done by plant hormones (or phytohormones). The plant hormones coordinate the activities of the plant by controlling one or the other aspect of the growth of the plant. So, the plant hormones are also known as plant growth substances. The growth of a plant can be divided into three stages : cell division, cell enlargement and cell differentiation (or cell specialisation), and these stages have particular locations in a plant. These three stages of plant growth as well as promotion of dormancy, breaking of dormancy, stomata control, falling of leaves, fruit growth, ripening of fruits and ageing in plants are controlled by the various plant hormones.

There are four major types of plant hormones (or phytohormones) which are involved in the control and coordination in plants. These are:

• Auxins,
• Giberellins,
• Cytokinins, and
• Abscisic acid (ABA).

Auxins, gibberellins and cytokinins are the plant hormones which promote growth of plants. On the other hand, abscisic acid is a plant hormone which inhibits (or prevents) the growth. Functions of the various plant hormones are given below:

• Promote cell enlargement and cell differentiation in plants. Auxins also promote fruit growth.
• Promote cell enlargement and cell differentiation in the presence of auxins. Gibberellins help in breaking the dormancy in seeds and buds.
• Promotes cell division in plants. Cytokinins also help in breaking the dormancy of seeds and buds. They delay the ageing in leaves. Cytokinins promote the opening of stomata. They also promote fruit growth.
• Abscisic acid promotes the dormancy in seeds and buds. It also promotes the closing of stomata. Abscisic acid promotes the wilting and falling of leaves.

Answer 2

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• The organic chemical substances produced in plants which control growth, development and response in plants, are called plant hormones.
• The example of plant hormones are : Auxins, gibberellins , cytokinins and Abscisic acid.