Here we are going to discuss “Plant Hormones: Growth Regulators – Promoters and Inhibitors in Details” Functions of plant growth promoters and plant growth inhibitors.
Plant Hormones are special class of chemical substances which controls growth and development of plants. Hormones are needed in small quantity at very low concentrations. Hormones are really effective at the site of their synthesis.
Starling used the term “Hormone” for the first time in 1906. Starling called it stimulatory substance.
The plant growth hormones are also known as phytohormones. Phytohormone term is coined by Thimann in 1948. Growth hormones or phytohormones are the organic substances which are synthesized in minute quantities.
Plant Hormones transported from their origin to another part where they influence specific physiological process a group of plant hormones including auxins gibberellins cytokinins ethylene and Abscisic acid are growth regulators
Plant Hormones: Plant Growth Promoters
Auxin, Gibberelline and cytokinin are considered as growth promoters. Plant growth promotors stimulate the growth in stem, leaves and fruits by different types of effects.
1. Auxins
Auxins control several types of plant growth processes which are very important to survive any plant. These are some important plant growth processes which are controlled by auxins.
- Cell Elongation- helps to promote elongation due to which growth of stems and roots occurs. Enlargement of many fruits occurs by stimulating elongation of cells in all the directions.
- Auxins, Solubilized carbohydrates, loosening of microfibrils, synthesis of more wall material increased membrane permeability and respiration these all the processes auxins and enlarge the cell.
- Apical Dominance -Auxins Promote the growth of apical bud and suppressed the growth of lateral buds, this nature is called apical dominance. Apical dominance is the process of faster growth of apical bud as compared to lateral Buds.
- Control of abscission layer-abscission layer promotes the fall of leaves and fruits. Do not allow the formation of the abscission layer. Abscission layer is produced when the amount of oxygen in the plant falls below a minimum.
- Weed control- auxins also helps to control weeds in the agricultural field. The weeds are unnecessary plants which grow with the crop and affects the agriculture crop negatively.
- Root Differentiation- those plants which are usually propagated by stem cutting auxins promote the root to stabilize the plant.
- Parthenocarpy- Auxines promotes the formation of seedless fruits.
- Flowering- Auxins also helps to promote flowering in pineapple.
Read Also- Plants Growth and Developments – All Important points
2. Gibberellins
- Stem elongation- gibberellins induce elongation of the internodes that’s why is time get elongated. Stem elongation results due to Rapid cell division and cell elongation induced by gibberellins
- Flowering- can initiate the flowering of a plant. This is common vernalised and long-day plants.
- Leave expansion- When leaves are treated with gibberellins they become broader and elongated.
- Reversal of dwarfism- this is the unique effect of gibberellins. Gibberellins can elongate genetic dwarf plants.
- Bolting effect- gibberellins can induce stem elongation in rosette plants this effect is called bolting effect.
- Along with these effects of gibberellins, enzyme formation, breaking of dormancy, parthenocarpy, sex expression, substitution for vernalization, malt yield, delayed ripening of fruits, seed germination is some other effects of gibberellins.
Read Also- Parthenocarpy: Definition, Types, Hormones, Advantages and Disadvantages
3. Cytokinins
- Cell division- cytokinins are very important for cytokinesis which is the step of cell division.
- Cell enlargement and differentiation- and hence the expansion of leaf cells under some conditions. Cytokinins play a very important role in morphogenesis and differentiation.
- Delay in senescence- cytokinin delivers the ageing of leaves and other organs by controlling protein synthesis process. Cytokinins also control the mobilization of resources.
- Lateral bud dominance- cytokinins promote the growth of lateral buds in plants whereas auxins promote apical dominance.
- Breaking of dormancy- cytokinins helps in the germination of seeds by breaking their dormancy.
- Besides these effects these are some other effects of cytokinin, Accumulation and translocation of solutes, sex expressions, enzyme activities, parthenocarpy, pomalin, initiation of interfascicular cambium, nucleic acid metabolism, protein synthesis, promotes flowering in some short-day plants.
4. Ethylene
- Ethylene is a gaseous hormone. Ethylene stimulates transverse growth of plants but retards the longitudinal growth.
- Ethylene promotes fruit ripening and its growth.
- Leaf bending is controlled by ethylene in many plants.
- Ethylene Stimulates the formation of the abscission layer.
- Ethylene inhibits the growth of lateral buds and promotes apical dominance.
Read Also – Embryo Development in Plants: Embryogenesis in Plants | Embryogeny
Plant Hormones: Plant Growth Inhibitors
Abscisic acid
Abscisic Acid is a growth inhibitor. This is a mildly acidic growth hormone. Abscisic Acid works as an anti gibberellic in nature because growth is primarily controlled by gibberellins. Abscisic Acid inhibits growth.
- Abscisic Acid acts as a growth inhibitor and induces dormancy of buds. The main cause of dormancy of seeds is abscisic acid. Abscisic Acid promotes the abscission of leaves flowers and fruits by forming an abscission layer.
- Abscisic Acid causes destruction of chlorophyll by which it stimulates the senescence of leaves. Abscisic Acid inhibits the synthesis of protein and RNA.
- Abscisic Acid can be used as it antitranspirant. Abscisic Acid partially closes the stomata and reduces the rate of transpiration.
Here we have discussed “Plant Hormones: Growth Regulators – Promoters and Inhibitors in Details” we hope you like this article. if you have any query or suggestion, please leave a comment on the email. or contact us from contact us page.
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