the Hormonal control of speed and a growth direction. Gibberelliny

you are: the Hormonal control of speed and a growth direction

One more group important rostovyh hormones of the plants, opened thanks to a number of casual circumstances and thin supervision, make gibberelliny. Last decade the last century Japanese risovody have found out on the checks occurrence of extremely extended sprouts. They began to observe attentively of these sprouts as the good farmer usually considers any large plant as a possible material for selection of a grade for the purpose of improvement of its general efficiency. however these high sprouts never lived before maturing and only occasionally blossomed. Illness has been named bakanae (illness ' bad sprouts '). In 1926 Japanese botanik Kurosawa has found out that these sprouts have been infected by a mushroom named later Gibberella fujikuroi (the representative kl. Ascomycetes, or marsupials of mushrooms). If mushroom support to transfer from the infected sprout on a healthy plant the last falls ill also its growth becomes abnormal.

At mushroom cultivation in a flask on the artificial environment in it any substance which, being collects is transferred on a plant-receptor, causes in it excessive growth - one of the symptoms typical for illness ' of bad sprouts '. This substance has been named gibberellinom (derivative from Gibberella).

In the thirties the Japanese physiologists and chemists managed to allocate from the environment on which grew up mushroom Gibber ella, some substances, ingibirujushchih and stimulating growth. The structural formula of a growth factor offered by them as a result gibberellina was not absolutely true. Nevertheless these scientists have correctly defined the general nature of substance and have received crystals at which drawing on examinees of a plant were observed typical for illness bakanae symptoms of very strong lengthening of a stalk. This information has been published in Japan in many articles till 1939, but, unfortunately, the Second World War has interrupted the begun work and has distracted attention of the majority of scientists to researches for the military purposes. The exciting history of opening gibberellina remained the unknown person in the West approximately till 1950 when some groups of researchers to England and the USA have found out old articles about gibberelline and again have started the decision of this problem.

By 1955 English scientists have confirmed the initial supervision made in Japan, and also have allocated substance which they named gibberellovoj acid (fig. 9.19). It differs from a material allocated with Japanese a little. Soon many other connections with the same basic structure were revealed both in mushrooms, and in not infected fabrics of the higher plants. It became clear that gibberelliny represent the whole family of molecules numbering now over 50 connections. All of them possess the basic tetratsiklicheskim gibberellanovym a skeleton, but each of them has various updatings and chemical groups (for example,-) in different parts of a molecule. Gibberellovaja acid at drawing on some plants causes excessive lengthening of a stalk, and in some cases and reduction of a sheet surface. The brightest display of its action is, perhaps, fast stimulation of lengthening of a pedicel (strelkovanie) and in many cases - flowering stimulation dlinnodnevnyh plants (see gl. 11 and 12; fig. 9.20). Gibberellin promotes arrow ejection, increasing as number of cellular divisions in certain zones, and a stretching of the cages formed by such divisions (fig. 9.21). When small amounts gibberellina are put only, the exit in an arrow occurs, but rudiments tsvetkov can and not be differentiated. Higher doses gibberellina usually cause not only strelkovanie, but also flowering. There is some data in favour of the statement that at dlinnodnevnyh plants the induction stimulates formation gibberellina in the long afternoon that in turn causes morfogeneticheskie reactions. In other cases activity gibberellina in apeksah plants decreases during their exit in an arrow that testifies to possible use gibberellina during this period. Gibberellin it is not capable to cause flowering at korotkodnevnyh plants and actually renders, apparently, opposite effect. While it is precisely not known, what hormones supervise flowering at korotkodnevnyh plants or at those dlinnodnevnyh plants which are extended, but do not blossom in reply to influence gibberellovoj acid. Probably that in the latter case acid is involved in a flowering induction, and any another gibberellin not gibberellovaja.

However not all plants react on gibberellin. Analyzing results of numerous tests, physiologists have found out correlation between the initial size of a plant and degree of its reactance in the relation gibberellina. If to compare, for example, dwarfish peas or dwarfish corn to their tall forms it is found out that drawing gibberellina on dwarfish plants causes their strengthened growth whereas at similar processing of tall forms the effect is insignificant or it is not present absolutely (fig. 9.22). As in many cases distinction between karlikovostju n vysokoroslostju is defined only by one gene, the attractive hypothesis According to which karlikovost it is actually caused by inability of a plant to produce enough gibberellina for satisfaction of the basic needs is offered. Hence, drawing gibberellina on some genetic dwarfs gives tall forms. Such dwarfish plants which have become high thanks to processing gibberellinom, of course, all the same will have dwarfish genotypes at reproduction will give dwarfish posterity.

The Organisms, which phenotypes are changed by means of chemical or physical processing so that they become similar to organisms with other genotype, are called fenokopijami.

It is established that some tall plants really contain more total gibberellina, than dwarfish plants, though it and not always so. However at hromatograficheskom division gibberelliny tall and dwarfish plants often find out some qualitative distinctions. In such cases karlikovost can be caused presence gibberellinov, less active in growth stimulation. But it is clear that karlikovost it is not always connected with anomalies in gibberellinah.

Gibberellin can induce also formation partenokarpicheskih fruits, operating independently or together with auksinom. As an example the apple can serve. Numerous attempts to achieve it partenokarpicheskogo developments by means of one auksina have not crowned success. Now spraying of plants by a mix auksina and gibberellina brings desirable results. Increase of the maintenance natural gibberellina in apple seeds correlates also with the period of their maximum growth that testifies to possible regulation gibberellinom seed and wall developments zavjazi. Last aspect of functioning gibberellina has found application in agriculture at cultivation beskostochkovogo grapes.

Gibberelliny play a part, possibly, not only in development of seeds, but also and in their germination. Thus they operate with two ways. First, they, apparently, promote an exit of seeds from a rest condition that it is possible to show easily, having put gibberellovuju acid on based seeds which after that sprout. Gibberellin replaces also light or low temperatures when for interruption of rest of seeds these are required razdrazhiteli. In the nature rest, possibly, interrupts at increase of the maintenance natural gibberellina (fig. 9.23). Secondly, in seeds of cereals gibberellin is that substance which supervises mobilisation of a spare nutritious material in endosperme. Seeds of many cereals, for example barley, contain the spare starch capable quickly to be hydrolyzed in the beginning of germination. After soaking of grains of the barley containing germs, fast hydrolysis of starch begins. If before soaking to remove germs in seeds tidroliza starch does not occur. At drawing gibberellina on such seeds deprived of germs starch begins gidrolizovateja (fig. 9.24).

Thus in a germ soon after swelling of seeds in norm, obviously, are formed gibberelliny, making active process of hydrolysis of starch by means of the special mechanism which will be considered in more details in following section. Two described effects gibberellina, seeds shown at germination, completely differ among themselves in the respect that rest interruption occurs in a germ before mobilisation of spare nutrients. Last process begins as a result of action gibberellina on alejronovyj a layer surrounding endosperm (fig. 9.25.)

Apparently, there are two ways of the control gibberellinom specific physiological processes. The first way it is simple synthesis gibberellina a plant and the subsequent initsiatsija gibberellin dependent process. The second way is more combined. Recollect that exist nearby 50 gibberellinov, differing on the relative activity depending on that process which they influence. As all gibberelliny have similar molecular structure, any of them can be transformed into another, only slightly having modified its molecule, for example having attached to it - IT-group in one or more positions from several possible. Thus, the plant can operate that or other internal process, transforming during a metabolism inactive gibberellin in active or on the contrary.

Similarly karotinoidnym to pigments, steroids and rubber, gibberelliny represent izoprenoidnye the connections formed from Acetyl-soa pridyhatelnom a metabolism (see gl. 5). The metabolic way of biosynthesis gibberellinov, found out with the help mechennyh 14С connections, is displayed by the following scheme;

Identification diterpenov as intermediate connections in biosynthesis gibberellinov proves to be true also that fact that retardant growth АМО-1618, operating as the antagonist gibberellinov, interferes with formation diterpena from its predecessor.

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