Plant Growth Promoters, Hormones, Regulators

Plant growth promoters

Today, we discuss the topic of plant growth promoters, plant growth inhibitors, plant growth hormones, and plant growth regulators.

What is mean by Plant growth promoters? The Plant growth promoters are the substances that develop the overall health and growth of the plants. The main benefits of plant growth promoters can be seen in the crop growth, quality of the final yield and productivity. Recommended for all types of crops, these are known as soil conditioners due to their positive effects on the soil quality. We have a wide stock of plant growth promoters among which, amino acids have the main share in the market.

Growth promoter is a natural or herbal fertilizer, specially designed for the overall growth of the plants. These Plant growth promoters are intended to accelerate the rate of growth and maturation of crops or plants, without disturbing their natural physiological actions. These premium quality plant growth promoters increase the yield as well as control the pests and pathogens. A highly efficient and safe biological tonic, this Plant growth promoter boosts an all round growth of the crops by regulating their metabolic activities from the root to the leaves. The product is obtainable in different packaging specifications, which can be tailored to specific needs.

Plant Growth Promoters are substances which develop the overall healthy growth and development of plants. These substances can be either synthetically produced or obtained from Biological derivatives. Plant growth promoters (PGP) are efficient in improving the crop, quality, and productivity significantly. Plant growth promoters, particularly biological derivatives are more effective and safe. They could be recommended for all crops or plants. Among the Plant growth promoters, the Amino acids are obtained biological sources like fish waste, animal waste, Plant protein like Soya bean, maize, groundnut, etc. The PGP’s promote cell division, cell enlargement, flowering, fruiting, and seed formation. Examples of Plant growth promoters are auxins, gibberellins, and cytokinins.

Plant Growth Regulators.
Plant Growth Regulators.

Read: Goat Fattening Techniques.

Based on their action, plant growth regulators are generally classified into two major groups: Plant growth promoters and Plant growth inhibitors.

Plant growth promoters are Auxins, Gibberellins, and Cytokinins and Plant growth inhibitors are Abscisic acid and Ethylene.

The top three plant growth promoters are:

  • Auxins
  • Gibberellins and
  • Cytokinins


Auxins are the best-known plant growth promoters. Auxins promote the growth of stem sections and decapitated means apex removed, coleoptiles, but in the same concentration are incapable of causing the development in intact plants.

What is meant by Auxins? Auxins are called as “An organic compound is explained by its capacity in low concentration to induce elongation in shoot cells and inhibition of elongation of root cells. They resemble Indoleacetic acid (IAA) in physiological action. They may and normally do affect other processes besides elongation but the elongation of shoot cells is considered as critical. These are weak organic acids. The major naturally occurring auxin is Indole-3-acetic acid (IAA).”

There are two main types of auxins:

  1. Natural auxins and
  2. Synthetic auxins.
  3. Natural auxins:

These are naturally occurring auxins in plant parts and, hence, regarded as phytohormones. The major universally present naturally auxin is Indole-3-acetic acid. And other natural occurring auxins are hidole-3-pyruvic acid, Indole-3-ethanol, Indole-3-acetaldehyde, etc. The natural auxins could occur in plants in the form of free auxins and bound auxins.

  1. Synthetic auxins:

These are the chemicals synthesized by chemists that cause various physiological actions similar to Indoleacetic acid. They are not treated as phytohormones but they are considered as plant growth regulators. Some examples of the synthetic auxins are Indole-3-butyric acid (IBA), Indole-3- propionic acid (IPA), α- and β-naphthalene acetic acid (NAA), 2, 4- dichlorophenoxy acetic acid (2, 4-D), benzoic acids, etc.

Effects of Auxins
  • Auxins promote flowering in plants like pineapple.
  • Help to initiate rooting in plant stem cuttings.
  • It prevents the dropping of fruits and leaves too early.
  • Promote natural detachment or abscission of older leaves and fruits.
  • It controls xylem differentiation and helps in cell division.
Functions of Auxins
  • Auxins used in the process of plant propagation.
  • Used by gardeners to keep lawns free from weeds.
  • Auxins are broadly used as herbicides to kill dicot weeds.
  • Auxins are used for the production of fruit without preceding fertilization.
  • Apical dominance could occur in which the growth of lateral buds is inhibited by the growth of apical buds. In such cases, the shoot caps could be removed.

Read: Cattle Fattening Methods.


Gibberellins are growth hormones that stimulate cell elongation and source plants to grow taller. Gibberellins have a role in other plant processes, such as stem elongation, germination, flowering, and fruit ripening.

Once a plant releases gibberellins, its cells begin a method of elongation. Because, plants are composed of single cells stacked on top of one another, this elongation of thousands of individual cells effects on the overall growth of the plant.

Gibberellins (GAs) are plant hormones or Plant growth promoters that regulate different developmental processes, including stem elongation, dormancy, flower development, and leaf and fruit senescence. Gibberellins, like auxins, are chemicals which have the capacity to influence both growth and expansion of plants. The first effort on the gibberellins resulted from Japanese investigations into the Bakanae disease of rice. Bakanae was for the first time statement by Konishi in the year 1809. At that time it was considered that the giant rice plants were one of the varieties of rice.


There exist more than 100 gibberellins get from a variety of organisms from fungi to higher plants. They are all acidic and are denoted as follows GA1, GA2, GA3, etc. GA3 (Gibberellic acid) is mainly noteworthy since it was the first to be discovered and is the most studied.

  • It affects increase the axis length in plants such as grape stalks.
  • Delay senescence i.e. ageing in fruits. As an effect, their market period is extended.
  • Help fruits like apples to elongate and develop their shape.
Functions of Gibberellins
  • Involved in leaf expansion.
  • Break bud and seed dormancy.
  • Promote bolting in cabbages and beet.
  • Used by the brewing industry for increasing the speed of the malting procedure.
  • Gibberellins are used as the spraying agent to increase sugarcane yield by lengthening of the stem.
  • Used to fasten the maturity stage in young conifers and promote early seed production
  • Helps in increasing the crop yield by increasing the height in plants such as sugar cane and raise the axis length in plants such as grape stalks.


The next type of plant hormone, the cytokinins stimulate the growth of cells in tissue culture or organ culture and have a marked increasing effect on cell division. The existence of specific substances which can control cell division in plants was suspected several years before such substances were finally discovered.


Cytokinins hormone was discovered as kinetin. Kinetin does not occur naturally, however, scientists later discovered several natural (an example is a zeatin) and synthetic cytokinins. Natural cytokinins exist in root apices and rising shoot buds areas where rapid cell division takes place.

Functions of Cytokinins
  • Break bud and seed dormancy.
  • Promotes the growth of the lateral bud.
  • Promotes cell division and apical dominance.
  • They are used to maintain flowers fresh for a longer time.
  • Cytokinins are used in tissue culture to induce cell partition in mature tissues.
  • Promote lateral shoot development and adventitious shoot formation.
  • Cytokinins promote nutrient mobilization which in turn helps delay leaf senescence.
  • Helps in delaying the procedure of aging (senescence) in fresh leaf crops like cabbage and lettuce.

Read: How to Keep Farm Records.

Plant Growth Inhibitors

Abscisic Acid

It is a plant hormone. Abscisic Acid functions in many plant developmental processes, including seed and bud dormancy and the control of organ size and stomatal closure. What is the main function of Abscisic acid in plants? Abscisic acid owes its names to its function in the abscission of plant leaves. In preparation for winter, Abscisic acid is formed in terminal buds. This slows plant growth and directs leaf primordial to increase scales to protect the dormant buds during the cold season.


  • Regulate abscission and dormancy.
  • Inhibit plant growth, metabolism and seed germination.
  • Stimulates closure of stomata in the epidermis.
  • It increases the tolerance of plants to different types of stress and is, therefore, called ‘stress hormone’.
  • Important for seed development and maturation.
  • Abscisic acid induces dormancy in seeds and helps them withstand desiccation and other unfavorable growth factors.


It serves as a hormone in plants. The first support of ethylene as a promoter of leaf senescence was observed in leaves and stems treated with ethylene. In particular, leaves exposed to ethylene could show yellowing, necrosis (death), and shattering. The first onsets of ethylene-induced senescence in plant leaves are the photosynthesis and chlorophyll reduction. However, the ethylene response is variable and depends on the species, because all plants or part of a plant has different sensitivity to this hormone.

Ethylene is the simplest unsaturated hydrocarbon, regulates several diverse metabolic and developmental processes in plants.

Effects of Ethylene

  • Ethylene affects horizontal growth of seedlings and swelling of the axis in dicot seedlings.
  • Promotes abscission and senescence, particularly of leaves and flowers.
  • Enhances respiration rate through the ripening of fruits. This phenomenon is called a ‘respiratory climactic’.
  • It increases root growth and root hair formation, therefore helping plants to increase their absorption surface area.

Read: How to Build A Greenhouse at Home.


  1. Sir, Please name a few Plant Growth Promoters / Regulators for apple plants, for proper growth of apple Plants alongwith there source of procurement and the method of use on plants


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