Plant hormones are also recognised as phytohormones. They are organic compounds that control the growth and development of plants. Auxins, gibberellins (GA), abscisic acid (ABA), cytokinins (CK), salicylic acid (SA), ethylene (ET), jasmonates (JA), brassinosteroids (BR), and peptides are all hormones produced by plants. A wide range of synthetic chemical molecules is used to improve the development of cultivated plants, grasses, cultured cells, greenhouse conditions, and cell organelles. These synthetic compounds are known as plant growth regulators (PGRs).

Plant Hormones:

Plants require natural light, water, oxygen, and nutrients to enhance and evolve. These are outside influences. Aside from these, a few inherent factors control plant growth and productivity. These are referred to as plant hormones or “Phytohormones.”

Plant hormone secretion compounds are found in plants in very small quantities. Hormones like indole (auxins), terpene (Gibberellins), adenine (Cytokinins), carotenoids (Abscisic acid), and gas derivatives (Ethylene) are released in nearly every plant part and are transferred to other portions of the plant.

They can work together or independently. Different hormones’ roles can be supplementary or antagonistic. Hormones and external factors play a significant role in processes such as vernalisation, phototropism, seedling growth, hibernation, and so on.

Exogenous application synthesised plant hormones are used to regulate crop production. Charles Darwin discovered phototropism in canary grass coleoptiles, and FW Went isolated auxin from oat seedling coleoptiles.

Rooting hormone is a combo of phytohormones that enhances a plant to produce root cells rather than green cells from leaf and stem material.

Primary functions of plant hormones:

Plant hormones regulate all aspects of progress and development in plants, including cellular division, augmentation, inflorescence, seed forming, hibernation, and abscission. Plant hormones are classified into two types based on how they work:

  • Plant Growth Enhancers.
  • Plant Growth Regulators.

Hormone Auxin.

The word auxin implies “to grow.” They are applied to crops and horticulture. They are found in the developing roots and stems before moving to other plant parts to carry out their functions.

 Indole-3-acetic acid (IAA), Indole butyric acid (IBA) are both natural (IBA). NAA, 2,4-D (2,4-Dichlorophenoxyacetic acid), and 2,4-D (2,4-Dichlorophenoxyacetic acid) are synthetic (Naphthalene acetic acid).

Functions of Hormone Auxin:

  • Helps in Stem and root cell elongation.
  • Parthenocarpy, or the growth of fruit without fertilisation, is induced, for example, in tomatoes.
  • Prevents premature leaf, flower, and fruit fall.
  • It is useful in stem cuttings and transplantation because it promotes rooting.
  • Promotes flowering, for example in pineapple.
  • 2,4-D is extensively used as a weedkiller to kill noxious weeds of dicot plants while causing no harm to monocot plants.
  • Contributes to cell division and xylem differentiation.

Hormone Gibberellins.

There are over 100 known gibberellins like GA1, GA2, GA3., and so on. They have an acidic pH. These can be observed at higher plants as well as microbes.

Functions of Hormone Gibberellins:

  • Bolting, or the rapid elongation of internodes well before flower initiation in rosette plants such as cabbage and beets, is encouraged.
  • Senescence is postponed.
  • Parthenocarpy is induced.
  • Dwarfism is inverted by stem lengthening.
  • Certain plants, such as cannabis, are induced to become male.

Hormone Cytokinins.

Cytokinins play an essential part in the process of cytokinesis. Cytokinins are naturally produced in plants in areas of quick cell division, such as root axils, shoot buds, and young fruits. Cytokinins move in a basipetal and polar fashion.

  • Natural: Isopentenyladenine, zeatin (corn kernels, coconut milk).
  • Synthetic: Kinetin, benzyladenine, diphenylurea, and thidiazuron are examples of synthetic compounds.

Functions of Hormone Cytokinins:

  • It encourages lateral shoot growth, which is used in culture to initiate shoot growth.
  • Aids in the removal of apical dominance caused by auxins.
  • Boost the creation of chloroplasts in leaves.
  • Increases nutrient deployment and slows leaf senescence.

Abscisic Acid Hormone.

It is a hormone that inhibits growth. ABAs neutralise gas. It suppresses plant metabolism and controls abscission and stunted growth. It is also acknowledged as a stress hormone in plants because it increases plant tolerance.

Functions of Abscisic Acid Hormone:

  • Causes leaf and fruit abscission.
  • Seed germination is inhibited.
  • Induces leaf senescence
  • Encourages dormancy in seeds, which is useful for storage.
  • Stimulates stomatal closure to avoid transpiration during water stress.

Plant Hormone Ethylene.

It is both a growth proponent and an inhibitor. Occurs as a gaseous state. It is produced in ripening fruits and tissue samples that are approaching senescence. It is one of the most extensively used hormones in agriculture and governs many physiological functions.

Functions of Plant Hormone Ethylene:

  • It accelerates fruit ripening.
  • Controls leaf epinasty.
  • Breaks the dormancy of seeds and buds.
  • Accelerates the elongation of petioles and internodes.
  • Promotes leaf and flower senescence and abscission.

Conclusion 

We discussed plant hormones, cytokinin, rooting hormone, and other related topics through the study material note on plant hormones. We also discussed the functions of Plant Hormones to give you proper knowledge. 

 Plant hormones are signal compounds generated within plants and occur in relatively low concentrations. Plant hormones regulate all components of plant development, from embryo development to organ size regulatory frameworks, pathogen defensive performance, stress resistance, and fertility progression.