Plant growth regulators: How to benefit from them

Plant growth regulators refer to the chemicals that can be used to influence the growth of a plant. These voluntary changes may include modifications like increasing return bloom, taller stem, increasing branching, suppressing shoot growth etc. The influence of PGRs is also dependent on a number of factors like absorption rate, weather condition, plant age and condition, what cultivar it is, and many more. PGRs are synthetic or natural depending on their function and can help modify the plant’s behaviour as needed.

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There are mainly five different classes of compounds pertaining to Auxins, gibberellins and their inhibitors of gibberellin biosynthesis, cytokinins, abscisic acid and compounds affecting the behaviour of ethylene. There are also products that block and reverse the action of these compounds just in case something goes wrong.

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See Also: What is seed propagation? What are its advantages?

Plant growth regulators: Five groups

Auxins: Auxins are a group of substances that are mainly growth-promoting. Although, at higher concentrations, they also can hinder the growth of lateral buds. Apart from being used as a plant growth regulator, auxins are also used as herbicides.

For instance, in the production of apples, a synthetic auxin known as naphthalene acetic acid (NAA) is used for thinning of fruit and for preventing fruit drop during a brief period before harvest.

Gibberellins: Gibberellins, also known as GA, is a plant growth regulator that promotes intracellular modifications, especially cell elongation, shoot growth, and regulation of dormancy. Compounds like promalin or perlan containing GA4+7 compound 6-benzyl adenine, have been used to alter factors like fruit size and reduce russeting in apple fruits.

Compounds like ProGibb 40sb and falgro that contain GA3 are used to make alterations like delayed ripening, improving fruit texture and firmness, and extending the harvest period in fruits like sweet cherries. Gibberellins are also used to manage flower saturation and overproduction in tart cherries.

Cytokinins: Cytokinins are a group of PGRs that promote cell division. They are involved in stimulating and branching bud initiation. Cytokinins are also used as fruit thinners in apples.
Abscisic acid: Abscisic acid is a plant growth regulator compound that helps steer the dormancy of buds and seeds. It also halts shoot growth and is involved in controlling water loss in plants.
Ethylene: Ethylene helps in regulating and promoting the abscission of leaves and fruits in plants. This plant growth regulator also helps inhibit shoot elongation and lateral bud development. Ethylene also plays a role in the development and maturation of plants.

Ethephon, which is a chemical compound, is a synthetic compound that releases ethylene upon application. Retention interferes with ethylene biosynthesis and lengthens a fruit’s storage life, and increases the duration for which it hangs onto trees.

Plant growth regulators: Benefits

When used in the right amount, PGRs can be super helpful for plants. They have a ton of benefits which can vary through different PGRs but have a positive impact on the plant’s overall growth. Some of these benefits include:

Uniform shape and size.
Improved flowering.
Improved foliage.
More water retention.
Compatible with a range of crops.

Plant growth regulators: Application

Application for PGRs is very simple but can get quite tedious in some cases. You should know that most plants absorb through the roots or stems.

As a general rule of thumb, apply 5-40 ml every ten litres for the first ten times with three-day intervals, 40-100 ml per ten litres for the next four times with seven-day intervals, and then 100-250 ml per ten litres for a single time. Other than that, follow basic guidelines on the packaging of whatever PGR product you use.