Growth and Development Regulators

Phytohormones - plant growth and development regulators - not only affect external manifestations( actual growth, flowering, etc.), but also to resistance to drought, the need for light and temperature, in short, everythingonly you can influence the plant.

The word "hormone" comes from the Greek hormaein - "exciting."In fact, at first it was stimulating hormones that attracted the attention of researchers, and only later it was discovered that hormones can both initiate and stimulate certain reactions, and inhibit them( there is nothing bad in this, sometimes the body needs to stop in time), so phytohormones, like all hormones, are rather regulators of growth and development in the broadest sense. And "phyto-", as already mentioned, means "plant" or "plant".

The first of the phytohormones was auxin, which gave the name to a whole class of phytohormones. Some of their varieties can be purchased in stores. Most often sold heteroauxin( IAA), produced in tablets of 100 mg, which must be diluted in water( 1 tablet per liter of water).Apply it traditionally to stimulate the rooting of petioles in slowly rooted species. Cuttings are immersed in the solution with cuts and kept in it for 8 to 24 hours, depending on the degree of lignification. Sometimes a powder mixture is used: up to 30 g auxin per 1 g of filler.

There are also available in the sale and its analogues: naphthylacetic acid( NAA), indolyl-butyric acid( IMC) and others. However, not all chemical relatives of auxin have the same properties. For example, herbicide 2,4-D - a substance designed to destroy plants! Is also a synthetic auxin. In general, many auxins( phenoxyauxins) have long been used precisely as herbicides. The fact is that stimulation of growth of accessory roots in petioles is not the main and not the only action of auxins, this is only the most frequent practical application of it.

First, auxins are responsible for differentiating the conductive tissue of plants( that is, forming it from the original almost identical mass of cells), the same vascular tissue, but which moves nutrients and metabolic products: for the plant it is an analogue of both the circulatory system anddigestive, and some others. There is no conductive tissue on the site - everything above it dies. Therefore, auxins in the laboratory are used as a medicine for some plant wounds.

Secondly, in woody plants auxins contribute to the formation and growth of xylem( in other words, growth in breadth: what is called wood in everyday life is called "secondary xylem" in scientific language).

Thirdly, auxin accelerates the growth of fruits, besides it does not just accelerate: under its influence, fruits can develop from dust-free and unfertilized flowers. For vegetable growing is not bad: with its help you can grow seedless cucumbers, tomatoes and eggplants. But if your goal is to get the seeds( and the flower grower usually needs them), work with the auxin cautiously, so that its drops do not accidentally fall on the flowers.

Fourthly, auxins are able to delay the loss of leaves( which is directly related to its first action: the leaf is retained on the plant due to vascular tissue).

Finally, recently in research laboratories work is under way to study the effect of auxin as an anti-stress factor, and although it is too early to talk about this role of this phytohormone, as official conclusions are not yet obtained, it can already be considered proven that auxin increases the resistance of the plantat least to drought and heat stress.

So how can such an amazingly useful substance serve simultaneously as a herbicide? Let us recall the remarkable medical aphorism: "There are no poisons or medicines, only different doses".Auxins in high concentrations are very toxic, and the most poisonous ones are chosen for the role of herbicides.

With auxins( as well as the majority of physiologically active substances) it is necessary to be treated very cautiously: with the wrong technology they can cause damage not only to the plant, but also to the person. In no case, when working with substances of this class, do not bring the contaminated hands to your face and be sure to wash them later.

Although for the sake of preserving trade secrets, the composition, as a rule, is not indicated in the specially produced "rooting stimulants", it is not difficult to guess that the auxin's relatives did not do without them. These drugs include Juka, Seradix, Rhiposon and others.

Auxins in a number of plants cause enhanced formation of another physiologically active substance - ethylene. Determination of the sex of flowers in monoecious plants occurs not without its participation: treatment with ethylene( as well as auxin) promotes the formation of female flowers, which can be used for breeding. The remaining manifestations of the action of ethylene are more interesting for gardeners( increasing the sugar content of fruits, accelerating their maturation, etc.).

Another class of phytohormones - cytokinins - is also actively used in plant growing and in flower cultivation in particular. Cytokinins( the most known of them kinetic) inhibit the aging of leaves, increase the bushiness of plants, with their help, you can achieve the emergence of a large number of female flowers.

In nature, they act together with auxins, also influencing the differentiation of cells, but also have a special function: they prevent the genes from "turning off", that is, stopping their active functioning( due to which, according to the latest scientific data, the plant is aging).It is known that the place of natural formation of cytokine in plants is the developing fetus, but not only it: according to one of the hypotheses, this physiologically active substance is synthesized by the plant in the roots, according to another hypothesis, its synthesis occurs in the region of rapid cell stretching near the shoot tip.

Gibberellins are not less interesting. The name of this class of phytohormones was received on behalf of the parasitic fungus, which causes "disease of rabid seedlings."The rice plants infected by it were incredibly fast stretched out in length, but were pale, frail and quickly lodged, so that the substance that caused this effect was at first recognized as harmful. Then it was found out that gibberellins are contained in all normal healthy plants, and the pathology itself caused their excess.

Gibberellins stimulate cell lengthening and thus ensure plant growth in height. Gibberellin-treated dwarf forms of plants can not be distinguished from normal, non-mutant forms. These hormones can also accelerate and germinate the seeds.

With the help of gibberellin you can suspend the rest period. The application of gibberellin induces the illumination and flowering of plants without the influence of a long day, it can be used to quickly obtain seeds from biennials. These same phytohormones also stimulate the growth of pollen tubes.

A high level of concentration of gibberellins contributes( in contrast to the action of auxins) to the formation of male flowers. But the development of the root system gibberellins not only do not contribute, but even hinder: this must be borne in mind.

Another known phytohormone is abscisic acid. It increases the resistance of many plants to drought.

There is one more interesting class of regulators of growth and development - retardants. This name has one root with the word retro - "back", "reversed".Retardants do not stimulate growth, but, on the contrary, are capable of inhibiting it, and often contribute to the development of lateral shoots. If you want to get a low, densely leafy plant, use their service.

Many retardants contribute to the development of underground plant organs: roots, tubers or bulbs;some extend the flowering period.

The most famous and affordable retardants are camposai and hydryl.

Warning! All phytohormonal drugs are highly toxic.