Difference Between Auxin and Gibberellin

Auxins and their role in plant growth were initially described in the 1920s by Dutch biologist Frits Warmolt Went. Kenneth V. Thimann was the first to isolate and characterise one of these phytohormones, identifying it as indole-3-acetic acid (IAA). In 1937, Went and Thimann co-authored Phytohormones, a treatise on plant hormones.

Auxin:

 Auxins (plural of auxin /ksn/) are a group of plant hormones (or plant growth regulators) that resemble morphogens. Auxins are important for plant body development and play a critical role in the coordination of various growth and behavioural processes in plant life cycles.

The discovery of auxins was the first of the primary plant hormones. Their name comes from the Greek word v (auxein, which means “to grow/increase”). Auxin can be found in all regions of a plant, although in varying amounts. Because the concentration in each site contains important developmental information, it is tightly regulated by metabolism and transport. As a result, auxin produces “patterns” of auxin concentration maxima and minima in the plant body, which regulate the development of individual cells and, eventually, the entire plant.

Auxin Functions:- Auxin hormones have a wide range of applications in plants. Auxin molecules can be present in all of a plant’s tissues. They are concentrated, however, in the meristems, the growth centres at the vanguard of growth. Auxin molecules are released from these centres and transferred to the roots. The plant can thus coordinate its size, as well as the growth and development of different tissues, based on the auxin concentration gradient.

Auxin has an impact on a variety of cellular functions. Auxin molecules can impact cytoplasmic streaming, fluid mobility within a cell, and even the functioning of numerous enzymes at the molecular level. As a result, auxin has complete control over the growth, development, and proliferation of individual plant cells. Flower initiation, fruit development, and even tuber and bulb formation are all influenced by the auxin gradient. Auxin levels affect processes like phototropism, which allows the plant to follow the sun and gain the maximum energy, even on a daily basis. Auxin regulates this process by concentrating on the plant’s side away from the sun. This induces cell modifications, causing the plant to bend toward the light.

Structure of Auxin:-

The amino acid tryptophan is used to make native auxin molecules. A six-sided carbon ring is connected to a five-sided carbon ring in this amino acid. A group is attached to this 5-sided ring. The sole distinction between most auxin molecules and tryptophan is the ring to which they are connected. The auxin IAA is a common auxin that may be observed below.

Two enzymes that act on tryptophan are required to make this compound. An amino-transferase removes a nitrogen and a hydrogen from the 5-sided ring’s side-chain first. The carboxyl group is then removed by a decarboxylase enzyme, leaving only COOH. IAA is formed when a chloride ion connects to the six-sided ring. The majority of auxins are derived from this molecule.

Gibberellin:-

 gibberellin is a hormone found in seeds, young leaves, and roots. Gibberella fujikuroi is a hormone-producing fungus belonging to the phylum Ascomycota that promotes excessive rice plant growth and yield. Gibberellins appear to encourage the growth of major stems, especially when administered to the entire plant, according to evidence. They also play a role in the bolting (elongation) of rosette plants (such as lettuce) when they are exposed to specific environmental stimuli, such as long periods of daylight.

Gibberellic acid, a gibberellin found in both higher plants and fungi, is offered commercially for horticultural and home gardening purposes. Bush beans may be transformed into pole beans, and dwarf corn can be transformed into regular corn with a few simple treatments. The most common application has been in the production of grapes. Gibberellin is commonly used in the culture of the ‘Thompson Seedless’ (‘Sultanina’) grape cultivar to increase fruit size, and it is also used to induce seedlessness in several other grape varieties.

Gibberellin Functions:-

Gibberellins have a role in breaking dormancy and other elements of germination in the natural world. The stored energy reserves of starch sustain the seedling until the photosynthetic machinery develops adequately in the early stages of germination. The degradation of starch to glucose in the endosperm usually occurs immediately after the seed is exposed to water during germination. Gibberellins in the seed embryo are thought to signal starch hydrolysis in aleurone cells by promoting the creation of the enzyme -amylase. Gibberellins (denoted by GA) produced in the scutellum diffuse to the aleurone cells, where they stimulate the secretion of -amylase, as shown in the model for gibberellin-induced synthesis of -amylase.

When a plant is subjected to cold temperatures, it produces a bigger amount of gibberellins. Cell elongation, breaking and blossoming, seedless fruits, and seed germination are all stimulated by these compounds. Seed germination is triggered by gibberellins, which function as a chemical messenger and break the seed’s dormancy. Its hormone attaches to a receptor, calcium activates the protein calmodulin, and the complex binds to DNA, resulting in the production of an enzyme that promotes embryo growth.

Structure of Gibberellin:- Gibberellin molecules of various sorts are produced in various sections of the plant. There are currently about 100 gibberellin molecules that can be identified. These chemicals are produced in a variety of plant cells, but they are concentrated in the roots. Auxin, on the other hand, tends to concentrate at the apex.  Gibberellin is a diterpenoid, which is a well-known and widely used biochemical substance. It is the building block of compounds such as Vitamin A and Vitamin E. Gibberellin A1, the first gibberellin discovered, is shown below.

Difference between auxin and gibberellin:-

Conclusion:- 

 Auxins (plural of auxin /ksn/) are a group of plant hormones (or plant growth regulators) that resemble morphogens. Auxins are important for plant body development and play a critical role in the coordination of various growth and behavioural processes in plant life cycles.Gibberellins have a role in breaking dormancy and other elements of germination in the natural world. The stored energy reserves of starch sustain the seedling until the photosynthetic machinery develops adequately in the early stages of germination. Gibberellin is a hormone found in seeds, young leaves, and roots. Gibberella fujikuroi is a hormone-producing fungus belonging to the phylum Ascomycota that promotes excessive rice plant growth and yield.