Phytohormones: Function & Diseases

Phytohormones, also called plant growth substances, growth regulators, or plant hormones, are biochemical signaling substances. They control the development of plants from germination to seed maturity. Unlike true hormones, which are produced in specific tissues and travel to their target site via the bloodstream, phytohormones transport their chemical messengers within the plant from the site of origin to the target site.

What are phytohormones?

When it comes to phytohormones, two different approaches are mentioned. Botany knows plant hormones as growth substances. Pharmacy understands phytohormones as ingredients that produce hormonal effects in humans. As a result, phytohormones have come to the attention of science because an alternative to hormone replacement therapy during menopause was sought. The artificial hormones that were supposed to help women against menopausal symptoms increasingly fell into disrepute because of their carcinogenic effects. Plant hormones, it was assumed, were more harmless because of their lower hormone concentration. This is only partly true. This is because plant hormones are also hormones that alter hormone metabolism. Phytohormones also differ significantly from real hormones. Plant hormones are primarily growth regulators. What they have in common with hormones is the ability to send signals over a long distance and to be highly effective even at low concentrations. Phytohormones are found in all cormophytes, the higher plants that have leaves, shoot axes, and roots.

Function, action and targets of phytohormones.

The hormone concept, which was originally developed for animal organisms, cannot be transferred one hundred percent to phytohormones. This is because plants do not have hormone glands, i.e., no fixed production sites. On the contrary, certain structures are only stimulated to create hormones by external influences. Thus, the site of formation and the site of action are not subject to strict separation. Phytohormones can both produce and exert an effect in the same tissue structures. Moreover, a phytohormone is capable of triggering completely opposite reactions in different organs. On the one hand, a plant hormone can promote flower growth, while at the same time inhibiting root growth. Phytohormones are divided into five groups. Three of them are growth-promoting plant hormones such as cytokinins, gibberellins and auxins. The other two are the inhibitory plant hormones ethylene and abscisic acid. In addition, there is the peptide hormone systemin. Salicylates, brassinosteroids and jasmonates also have an important function, and recently the chemical group of strigolactones has also been recognized as a plant hormone. Among other things, these are responsible for seed germination. As signaling molecules, phytohormones not only control plant growth, but also act as coordinators. Plant hormones are transported from the site of their formation to a target site. This occurs either from cell to cell, across the space between cells, or via specific pathways. The hormone action itself is caused by the activation of specific genes, which are controlled by certain hormone-sensitive initiators. The effectiveness of a hormone is determined by its concentration and the sensitivity of the cell responding to the phytohormone. It is not uncommon for several plant hormones to be involved in the regulation of a particular physiological process. In this case, it is not the concentration of the individual phytohormone that is decisive, but the interaction of all of them and their relationship to each other. The developmental process in a plant is based on a finely tuned, reciprocal interplay. The growth of leaves, shoots and roots can be inhibited, promoted or triggered. Phytohormones also control dormancy, plant movement, and light agility.

Application and characteristics of phytohormones.

Humans take in a certain percentage of phytohormones every day through their food, but it is in the milligram range. This gave scientists the idea of replacing the artificially produced hormones against menopausal symptoms with phytohormones. Isoflavones from red clover, prenylnaringenin from hops, or lignans from flaxseed act similarly to sex hormones and influence hormonal processes. This has brought various plants into focus.Black cohosh stimulates estrogen formation, but at the same time inhibits the progestin. The isoflavones in red clover can normalize excessive estrogen formation. These isoflavones are said to have a stronger effect than those from the soy plant. Monk’s pepper, with its iridoid glycosides such as agnuside and aucubin, is able to boost the body’s own progesterone production. However, the mechanism of action is not yet completely clear. Hops were long known only for their sleep-inducing effect until their estrogenic effect was discovered. This effect is mainly due to the estrogenic flavonoid hopein (8-prenylnariingenin). This substance activates the estrogen receptor. The estrogen-like effect also repeatedly leads to discussions about men who drink a lot of beer and develop a slight feminization in the form of a breast attachment. This also highlights another side of phytohormones. Not everything herbal is harmless. For example, some isoflavones, such as genistein from the soy plant, have been found to cause a change in genetic material. Admittedly, such results come from the laboratory and are only harmful above a certain concentration. Nevertheless, medical experts warn against taking phytohormones in an uncontrolled manner. Especially since it is known that plant hormones also promote the growth of tumor cells. Overall, the effect of phytohormones on the human organism is not yet fully understood. Despite minor side effects, they should not be taken for longer than three months. In particular, patients suffering from cancer should use phytohormones only after medical consultation. In case of pain, cramps, fever or bleeding, a doctor must be consulted immediately.