The phytohormone, also called plant hormones , are chemicals used by plants to generate physiological responses to long distances.
In this sense, they are similar to animal hormones, but the main difference is that plant hormones are generated in specific body tissues (such as insulin in the pancreas, for example), while phytohormones are generated by any plant tissue.
Another difference is that phytohormones affect the tissue that synthesizes them or other parts of the plant, while animal hormones do not affect the tissue that generates them.
While animal hormones are transported through the circulatory system of the blood, phytohormones travel through plants using xylem (a system of conductive vessels that carry water from roots to leaves) or phloem (which carries sap with nutrients from the leaves to the rest of the plant).
Phytohormones are responsible for a wide range of physiological processes in plants , such as root and stem growth, flowering, fruit ripening or leaf drop.
Some of these processes involve a single phytohormone, while others require the presence of several. There are also antagonistic plant hormones, which mutually block each other by acting on opposite processes. This is the case, for example, of gibberellins and abscisic acid.
Main phytohormones
Auxins
Auxins are perhaps the best known phytohormones, involved in cell growth and elongation processes . They are synthesized in the apical stems and transported to the rest of the plant, producing a concentration gradient.
They are present in plants, fungi, algae and bacteria, always associated with growth phenomena. The most widespread auxin in nature is indoleacetic acid. They are used in agriculture to promote crop growth.
Gibberellins
These plant hormones fulfill a complementary function to that of auxins. While auxins promote longitudinal stem growth, gibberellins promote lateral stem growth.
Both phytohormones are combined so that the plants grow properly, avoiding stems that are too thin or too short. A deficit of gibberellins in crops causes the plants to suffer a “lodging”, that is, they fall with the wind. Another function of gibberellins is to interrupt the dormancy period of the seeds so that they begin their germination.
Abscisic acid
Abscisic acid is a plant hormone antagonist to gibberellins in the role of seed germination, as it causes them to go into dormancy . It receives its name since it intervenes in the process of abscission of organs in plants, that is, the fall of leaves and fruits.
Ethylene
Ethylene is a gas that is used in industrial processes, for which it is artificially synthesized. In plants it intervenes in fruit ripening processes and is the main responsible for the fall of the leaves .
It is a volatile compound, so the ethylene generated by a plant affects nearby plants. A striking example that is present in many homes occurs when citrus fruits ripen and a green or white cottony layer forms.
These are molds of the genus Penicillium (from which penicillin was first obtained, hence the name), which emit a large amount of ethylene. This causes nearby fruits to ripen in a short time, favoring them to be infested by mold.
For this reason, it is important to get rid of fruits that are beginning to be covered by mold. Ethylene has applications in agriculture as it allows to harvest the fruits that are still green and make them artificially ripen by applying ethylene when they are going to be sold.
Cytokinins
These plant hormones are involved in cell division processes, promoting the growth of different organs (particularly fruits) and plants . Cytokinins have industrial applications similar to those of auxins, being used to promote growth. They have the advantage that the amount required for a response to occur is very low.
Jasmonic acid
Jasmonic acid is a volatile phytohormone that intervenes in defensive processes against herbivores or pathogens . Its presence induces responses in plants such as the generation of toxic compounds or lignin, a compound that lines plant cells and is very difficult to digest.
Applications of vegetable hormones lasa
The discovery of phytohormones is relatively recent, and all the compounds involved in plant physiological processes and the complete metabolic pathways of some already discovered phytohormones are not yet known.
It is an extremely interesting field for agriculture, as it allows a better use of crops.
For example, the use of ethylene to coordinate the ripening of the fruits and to be able to carry out the entire harvest on a desired date allows reducing costs in production. Likewise, improving plant growth through phytohormones allows it to occur more quickly and yield greater.
It also allows optimizing times during the transport of vegetables, avoiding combinations that may make certain vegetables ripen during the transport of goods, for example, in containers.
