Growth substances synthetic

In view of the great agricultural importance today of the synthetic plant growth substances in controlling the growth of plants of economic importance, details of the history of this development of investigations on plant hormones are presented. 

HubHtanwH, wlifitnvor tho dinxitinn of tho roflponno. Tho terms "regulator, "hormone, and antiauxiu will not be used for synthetic growth-substances. 

Hamence, J. H. (1946). The determination of auxins in soils, including a note on synthetic growth substances. Analyst 71,111-116. 

C4H,N02,Mr 101.1 l,mp. 229-231 °C. A non-proteinogenic amino acid first known as a synthetic product and later isolated from pears and apples. ACC is formed from methionine via 5-adenosylmethionine with the help of ACC synthase (EC 4.4.1.14) and cleaved by ACC oxidase to the multifunctional plant growth substance ethylene which plays key roles in various plant physiological processes such as ripening of fruit, aging, germination, and response to stress. 

Auxins. Term for naturally occurring or synthetic plant growth substances which resemble the natural plant hormone auxin ( 3-indolylacetic acid) in their activities. In low doses A. have growth stimulating activities and at higher doses herbicidal effects. 

Four main classes of natural and synthetic plant growth substances are distinguished 1) The 3-indolylacetic acid derivatives (lAA) and other C-3 substituted indoles, previously known as auxins, induce a pronounced longitudinal growth, stimulate the formation of roots and flowers, the activity of the cambium, and influence fruit ripening and numerous other developmental processes in the plant. In the literature many compounds with different constitutions are also designated as auxins if they have activities similar to those of lAA. These include, e. g., 2-naphthyloxyacetic acid, benzoic acid, phenoxycarboxylic acid derivatives. 

An adequate supply of the vitamins, then, depends on a succession of events. First, the sparing substance must not be completely absorbed before it can reach the cecum. Second, there must be present the appropriate microorganisms, the growth and synthetic ability of which can be stimulated by the unabsorbed substance. Third, the animal must eat its feces in order to obtain the synthesized vitamins excreted in them. 

In no other sector of biochemistry and physiology has the isolation of an ergon and the elucidation of its structure been followed by such a synthetic activity as when Kogl et al. in 1934 found indoleacetic acid (lAA, I) to be a naturally occurring plant growth substance. Nor has the harvest of active analogues ever been so abundant, resulting in such a diversity of practical applications. ... 

Cell Division and Root Formation. The formation of adventitious and side roots emanates from certain pockets of cell division which, in the case of side root formation, are located in the pericycle. The cell division leading to root formation is stimulated by lAA. For this reason preparations of lAA or synthetic growth substances producing a similar effect are used by plant growers to induce root formation in cuttings. 

A delay of senescence can also be produced in some cases with lAA, synthetic growth substances and gibberellic acid. However, the effect of these other phytohormones is much less pronounced. With the cytokinins the effect is, on the contrary, so striking that a few assay procedures for cytokinins are based on it. 

A large number of synthetic substances is known, some of which function as growth substances, others as inhibitors. In practice they are often preferred to the naturally occurring regulators. A few of them will be mentioned. 

Originally, the term antibiotics referred to substances produced by microorganisms that suppressed the growth of other organisms. Today, the term antibiotics often includes synthetic antimicrobial agents. 

---