The indoleacetic acid is an organic compound whose molecular formula is C8H6NCHtwoCOOH. It is a monocarboxylic acid that has an important role as a plant growth hormone, which is why it belongs to the group of phytohormones called auxins..
It is also known as 3-indoleacetic acid and indole-3-acetic acid. It is the most important auxin in plants. It is produced in these in the parts where there is growth, such as the shoots, young growing leaves and reproductive organs.
In addition to plants, some microorganisms also biosynthesize it, especially those called "growth promoters." Generally, these microbes are found in the rhizosphere or area adjacent to the roots of plants, favoring their growth and branching..
Indoleacetic acid biosynthesis occurs in several ways, most notably tryptophan, an amino acid present in plants.
In people with chronic kidney disease, the presence of high levels of indoleacetic acid can cause damage to the cardiovascular system and dementia. Various ways of using indoleacetic acid-producing fungi and bacteria are being studied to promote plant crops in an environmentally friendly way..
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Indoleacetic acid has a benzene ring in its molecular structure and attached to this a pyrrole ring in the 3 position of which a -CH group is attached.two-COOH.
- Indoleacetic acid
- Indole-3-acetic acid
- 3-indoleacetic acid
- Indolylacetic acid
- Skatole-ω-carboxylic acid
Colorless to white solid flake
175.18 g / mol
168.5 ºC
Very slightly soluble in cold water: 1.5 g / L
Soluble in ethyl alcohol, acetone and ethyl ether. Insoluble in chloroform.
Indoleacetic acid is the most important phytohormone or auxin of plants, which produce it mainly in places of the plant where there is growth.
The common way in which plants store indoleacetic acid is conjugated or reversibly linked to some amino acids, peptides and sugars.
It can be transported actively from cell to cell or passively by following phloem sap over long distances.
In addition to its production in plants, several types of microorganisms also synthesize it. Among those species of microbes are Azospirillum, Alcaligenes, Acinetobacter, Bacillus, Bradyrhizobium, Erwinia, Flavobacterium, Pseudomonas Y Rhizobium.
Most plant stimulating bacteria and fungi, including those that form symbiosis with them, produce indoleacetic acid. These microorganisms are said to be "growth promoters".
Indoleacetic acid biosynthesized by plant-associated bacteria or fungi in the rhizosphere plays an important role in root development.
However, microbes do not require indoleacetic acid for their physiological processes..
The explanation is that as plants grow, they release many water-soluble compounds such as sugars, organic acids and amino acids, which are transported to the roots..
In this way, the rhizobacteria obtain an abundant supply of material that is used in the production of metabolites such as indoleacetic acid, which is then used by the plant..
As can be deduced, this is an example of a partnership for mutual aid.
Indoleacetic acid is involved in various aspects of plant growth and development, from embryogenesis to flower development.
It is essential for many processes, such as seed germination, embryo growth, root initiation and development, leaf formation and shedding, phototropism, geotropism, fruit development, etc..
Regulates cell elongation and division, as well as their differentiation.
Increases xylem and root growth speed. It helps in the improvement of the length of the root by increasing the number of branches of the root, the root hairs and lateral roots that help in the taking of nutrients from the surroundings..
It accumulates in the basal part of the root favoring their gravitropism or geotropism, thus initiating the curvature of the root downwards. In some species it stimulates the formation of random roots from the stems or leaves.
It accumulates at the site where the leaves will originate, controlling its location on the plant. A high content of indoleacetic acid stimulates the elongation in the shoots and their phototropism. Regulates leaf expansion and vascular differentiation.
Together with cytokinins, it stimulates the proliferation of cells in the cambial zone. Contributes to the differentiation of vascular tissues: xylem and phloem. It influences the diameter of the stem.
Ripe seeds release indoleacetic acid which accumulates in the part that surrounds the pericarp of the fruit. When the concentration of indoleacetic acid decreases in that place, the detachment of the fruit is generated.
Indoleacetic acid is biosynthesized in actively dividing plant organs such as shoots, root tips, meristems, vascular tissues, young growing leaves, terminal buds, and reproductive organs..
It is synthesized by plants and microorganisms through several interrelated pathways. There are pathways that are dependent on tryptophan (an amino acid present in plants) and others that are independent of this.
One of the biosynthesis starting from tryptophan is described below..
Tryptophan through the enzyme aminotransferase loses an amino group and becomes indole-3-pyruvic acid.
The latter loses a carboxyl and indole-3-acetaldehyde is formed thanks to the enzyme pyruvate decarboxylase.
Finally, indole-3-acetaldehyde is oxidized by the enzyme aldehyde-oxidase to obtain indole-3-acetic acid..
Indoleacetic acid in the human body comes from the metabolism of tryptophan (amino acid contained in various foods).
Indoleacetic acid is elevated in patients with liver disease and in people with chronic kidney disease..
In the case of chronic kidney disease, high levels of indoleacetic acid in blood serum have been correlated with cardiovascular events and mortality, turning out to be significant predictors of them.
It is estimated that it acts as a promoter of oxidative stress, inflammation, atherosclerosis and endothelial dysfunction with a procoagulant effect..
High levels of indoleacetic acid in the blood serum of patients receiving hemodialysis have also been associated with decreased cognitive function..
There are several ways to obtain it in the laboratory, for example from indole or from glutamic acid.
New strategies are being studied that allow the use of indoleacetic acid to increase the productivity of crops with minimal impacts on the natural environment, avoiding the environmental effects of chemical fertilizers and pesticides..
Certain researchers isolated some endophytic fungi associated with medicinal plants from arid environments.
They found that these fungi favor the germination of wild-type and mutant seeds, and after certain analyzes it was deduced that the indoleacetic acid biosynthesized by such fungi is responsible for the beneficial effect..
This means that thanks to the indoleacetic acid that these endophytic fungi produce, their application can generate great benefits to crops that grow on marginalized lands..
Other scientists managed to devise a genetic manipulation mechanism that favors the synthesis of indoleacetic acid by a type of rhizobacteria, this being normally not a promoter of plant growth.
The implementation of this mechanism led these bacteria to synthesize indoleacetic acid in a self-regulated way. And the inoculation of these rhizobacteria to the roots of plants of Arabidopsis thaliana improved root growth.
It has been possible to synthesize a compound conjugated or formed by the union of indoleacetic acid and carbendazim (a fungicide) that, when inoculated in the roots of legume seedlings, exhibits both fungicidal properties and effects that promote plant growth and development. This compound still needs to be studied in greater depth..
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