Abstsizovaja stress acid-hormone. Rest and germination of seeds

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Rest of seeds, as well as winter rest of kidneys listopadnyh trees, obviously matters for a plant survival. Really, if seeds sprouted right after their maturing in the autumn the gentle sprout could get under the first frosts. Presence in enough seed ingibitora, such as ABK, guarantees absence in it metabolic activity during a winter season. With germination of many seeds interfere ingibitory, found out or in a cover of seeds, or in the remained bodies of a flower, or in fabrics of the fruit surrounding a seed. Often germination can be induced by careful vysolazhivanija seeds in flowing water. Though it is obvious that the plant can use many various kinds ingibitorov for rest achievement, ABK, probably, is one of the most important. For example, at an ash-tree (Fra-xinus americana) ABK is present at all fabrics, but the highest concentration are found out in a seed and okoloplodnike based fruits.

In the nature rest of seeds usually interrupts at storm rains, on light or under the influence of low temperature. At deserted plants the rest induced ingibitorami, interrupts, when seeds get under a storm rain. The system usually participates in the light control of germination fitohromnaja (see gl. 11). For seeds at which rest interrupts under the influence of a cold, low temperatures (2 5°С) within 4-6 weeks are necessary (see gl. 12). As at cooling seeds gradually leave a rest condition, the maintenance in them ABK falls, whereas the maintenance of hormones activating growth, such as gibberelliny, increases or during all cold period, or at once after its termination.

After interruption of rest seeds can sprout. Under favorable conditions in the spring - warm weather and sufficient maintenance with water and oxygen - speed of a metabolism raises. If to add water to the dry seeds which have left a condition of rest it is frequent already through 15 mines in a germ fiber synthesis begins. There can be also a synthesis mrnk, coding some of these fibers. But in some cases, for example in cotton seeds, fiber synthesis precedes synthesis new mrnk. It can be caused that present at based seeds mrnk, formed during seed development during the previous vegetative period, remains in a germ for a long time when in seeds not enough water contains. Such mrnk it is ready to translation at once after hydration of seeds. These long-living mrnk usually code enzymes, such, as proteaza and izotsitrataza in the cotton fabrics, participating in splitting of stocks of nutrients. At a cotton mrnk which synthesis is necessary on an interval of time making first 60% of the period of development of a germ, it is directly broadcast with formation of the fiber necessary for development of a germ. Throughout the others of 40% of the period of development of a germ the considerable part synthesised mrnk is postponed in a stock and not broadcast before germination.

We needed to find out, how metabolism RNK in a cotton germ changes in process of its development and that interferes with immediate translation long-living RNK after their formation. One key to a solution is given by experiences in which it is shown that washing of seeds eliminates inhibition of translation based mrnk whereas addition to seeds of washing water or ABK leads again to translation blocking. The unripe seeds of a cotton contain ABK which, probably, interferes with translation mrnk with formation of the enzymes necessary at germination. ABK appears in zavjazi a cotton only after zavjaz reaches 60% of its final size (fig. 10.13) that coincides with rupture of the vessels connecting zavjaz with other parts of a plant. Before other substance arriving from a plant probably hormone, for example tsitokinin, supports cellular division in zavjazi and activates a transcription of that part of DNA on which it is formed mrnk for germination enzymes. after rupture of vessels receipt of this substance stops. Formation ABK as a result begins, synthesis of DNA and cellular division stop, and mrnk for germination enzymes is transcribed, but not broadcast. When cotton seeds ripen, ABK is not formed any more and its level eventually decreases thanks to numerous vysolazhivaniju seeds in the rain, and also, probably, and owing to it fermentativnogo splittings. Therefore present at a seed mrnk it appears ready to translation as soon as the mature seed will absorb water from soil that it is possible to consider as the first stage of germination.