Plant growth hormones are set of biochemical secretions inside the plant and its parts which regulate the growth, enlargement, multiplication of the tissue, and cells.
They control the rate and extent of plant growth starting from seed germination, after growth, flowering, fruit formation, ripening, wilting, falling of leaves, etc.
Based on these facts modern scientists have developed synthetic plant growth hormones.
These synthetics hormones are used to increase the growth, flowering, fruit ripening etc in agriculture, horticulture, gardening.
Lack of these hormones can cause deficiency diseases. To rectify these synthetic hormones are used.
Plant growth regulators & plant growth hormones
- Abscisic acid.
Auxin; They have a prominent role in the entire growth of plants. They guide the seedling during the germination of plants from the seed stage in such a way that roots go into the soil while stem moves up towards the sun. So auxin does it by phototropism (moving to light for stem) and geotropism (moving towards soil for roots) mechanism.
Further, they promote plant elongation towards the sky and also towards the ground deeper by stem and roots respectively. This auxin is highly active in the tips of the shoot (stem) and also root tip.
They induce cell elongation, inhibit falling of leaves, and accelerate flower formation.
Gibberellin: These have a different role in promoting growth. They especially focus on elongating the nodes and also forming internodes. Nodes are those ridges or ring-like structure seen on the stem of bamboo, sugarcane, etc. These gibberellins enhance elongation of a node and when the node is long enough they form an internode in between. Thus promote the growth of the plant.
They induce stem elongation, promote flowering, leaf expansion, seed germination, etc.
Cytokines: The name comes from its ability to divide the cells. These participate in the growth of the plant by enhancing the cell multiplication. They increase the rate of cell division and mitosis in growing parts of the plant. Thus promote profuse tissue formation necessary for growth. It has anti-auxin, anti-gibberellin property. Helps in the conservation of water in plants during water deficiency.
Abscisic acid: This hormone is a natural growth inhibitor. It has a role in some stage of plant growth like the ripening of raw fruits etc. Thus they are involved in the growth of plants to a certain extent.
Ethylene: Ethylene is a gaseous phytohormone. It is also a growth inhibitor like abscisic acid. It is mainly involved in fruit maturation and ripening.
It also shows cell enlargement, geotropism i.e growing towards earth, fruit ripening, etc.
Tips to enhance plant growth hormones:
Plant growth hormones as shown above have diverse roles and some of them benefit yield in agriculture, flowering, fruiting, etc. But the internal levels of hormones are always spontaneously controlled and depend on the season, fertility of the soil, climate, genes, and stages of growth. So to enhance these hormones scientists go for
♦Biotechnological modification of genes related to these hormones.
♦External application of synthetic hormones.