A comprehensive guide on plant hormones

Phytohormones or better known as the plant hormones are those substances in the plants which control the growth and regulate it accordingly. These hormones are organic substances and there is a wide range of plant hormones produced in a plant. Some of the commonly known phytohormones in biology are cytokinins, auxins, salicylic acid etc.

What Are Plant Hormones?

Basically, plant hormones are the molecules which are produced inside the plant in very minute concentrations and functions to impart signals. Sunlight, water, carbon dioxide etc. are all the external factors which helps the plant to function and work but the phytohormones are the internal factor which are an intricate part of plant growth and development.These phytohormones are the controlling element in the plants which keeps complete check on the growth, the development of a plant beginning from the formation of embryo to the developing of organs, to the defence from the pathogens, to those stress tolerating, till the reproductive process ongoing in the plant.

Moreover, the speciality of the phytohormones are these are produced by each and every cell in the plant unlike in animals where a particular gland produces the particular hormone and the production is somewhat restricted. 

The basic function of the plant hormones are:

• Affect the growth of a plant
• Influence the development in plants
• Promote processes of cell division
• Initiate formation of tissues
• Helps to promote processes like germination, vernalisation, phototropism etc.

These phytohormones are basically the chemicals produced in the plants which through passive ways move into all parts of the plants. 

Hormones in plants

Plants grow, bear fruits, produce oxygen and therefore develop and all this takes place due to production of the phytohormones. There are many types of phytohormones in a plant and each serves their own role accordingly. Phytohormones tend to play two kinds of role. One is to promote and the other is to regulate and the therefore on the basis of the working of these plant hormones they are categorised into two, which are:

• Plant growth promoters
• Plant growth inhibitors

More about plant growth promoters

Plant growth promoters are those plant hormones which help the plants to grow and develop. There three main plant growth promoters which are:

• Auxins

Auxin is a phytohormone which helps the plant to grow. The term auxin itself means “to grow”. Auxins is a much required and in demand plant hormone in agriculture and horticulture. Auxins are mostly found in the tips of the stems and roots of the plant and from there they travel to various parts of the plants. Tips of stem and root are the portions in the plants from where the plant grows and hence auxins are mostly present here. The basic functions of these auxins is to elongate the cells in stems as well as roots, avoiding the premature falling of flowers, leaves, which promotes the rooting process in grafting. Additionally auxins also lead to the differentiation of the xylem.

• Gibberellins

Another important phytohormone categorised under growth promoters is ‘Gibberellin’. Basically acidic in nature, these chemicals lead to growth of stems, reduce dwarfism and break the seed dormancy process. Gibberellins are available in more than 100 kinds and function to induce the parthenocarpy and even delay the senescence.

• Cytokinins 

One of the important growth promoters in a plant is the cytokinin. This phytohormone is named after the process cytokinesis where this plant hormone is the key element. A naturally produced chemical, this cytokinin is produced in those parts of the plant where the cell division occurs.

Cytokinins are known for influencing the shoot growth and promoting the growth of chloroplast. Additionally, this phytohormone functions to overcome the apical dominance and lead the nutrient mobilisation.

More about Plant Growth Regulators

The chemicals produced in the plants which tend to regulate the growth of plants are said to be plant growth inhibitors. These phytohormones inhibit or regulate the development and growth of the plants. One of the basic plant growth inhibitors is Abscisic Acid.

Abscisic Acid: abscisic acid is one of the phytohormones but this works oppositedly as compared to auxin. This phytohormone is a growth regulator. The basic work of Abscisic acid is to inhibit the metabolism in plants and stop dormancy. This hormone is also known as the stress hormone, increasing the tolerance capability of the plant.

Conclusion

Plant hormones are a key in the growth of plants. Hence there are 5 basic plant hormones which are the Auxin, gibberellins, cytokinin, abscisic acid and the last is ethylene plant hormone whose basic function is to ripen the fruits.