Growth and formoobrazovanie at plants. The general review. The summary

you are: Growth and formoobrazovanie at plants. The general review

The Mature plant develops from a germ as a result of a number koordinirovannyh the events which general course is programmed in genes, and the real embodiment depends on an environment. Growth at length is connected, first, with formation of new cages in the centres of cellular division (meristemah), the stalks located on tops, roots and kidneys, and, secondly, with lengthening of these cages. In the same way and growth at thickness occurs by formation and the subsequent stretching of the new cages generated in this case lateralnoj (lateral) meristemoj, or kambiem, lying down (usually in the form of the single-row cylinder) between wood and a bark. Differentiation name process in which result formed meristemoj identical cages eventually become different and get specific characteristics.

The Seed consists of a germ, a stock of nutrients in endosperme or in fleshy cotyledons of a germ and from a seed cover. Germination comes after the seed will absorb enough of water and in it processes of cellular division and a stretching will begin. Growth rate happens in the beginning small (log-phase), then logarithmic dependence of growth rate on time (broad gull-phase), and later growth is supported again slowed down and at last stops in general. Life expectancy at different kinds of plants varies from several weeks till 3000 years and more. However on artificial nutrient mediums it is possible to grow up long beyond all bounds, by resowings, a fabric even those plants which in norm quickly finish the life cycle. The fabrics cultivated thus, remain usually not differentiated, but by means of corresponding chemical substances including hormones, in them it is possible to cause differentiation.

Young roots are covered epidermisom, consisting of the flat cages which are carrying out protective function, and the root hairs adapted for vsasyvanija of water and dissolved in it of mineral substances. The central part of a root occupies ksilema with its water spending fabric consisting from traheid and vessels, parenhimnsmi cages and fibres. Around ksilemy settles down floema, consisting of sitovidnyh tubes, cages-companions and parenhimnyh cages; on floeme the water solution of organic substances moves. Knaruzhi from floemy the pericycle - an educational fabric in which the lateral roots, punching to themselves a way outside through external fabrics arise lies. All this central cylinder, or stela, is surrounded endodermoj in which cages there are water-proof corbels of Kaspari. Thereof the current of the dissolved substances moving earlier on damp cellular walls, changes here the way and moves further already through membranes. Between the central cylinder and epidermisom the primary bark often playing a role of the reserving fabric settles down consisting of parenhimatoznyh cages. when kamby, lying between ksilemoj and floemoj, it is activated, epidermis and a part of a primary bark under the pressure of an internal gain rastreskivajutsja and are dumped. Cracks are tightened thanks to activity new meristemy - pith kambija, forming a new protective fabric - peridermu. Stalks on the structure are similar to a root though differ from it a number of signs: as a rule, they have consisting of parenhimnyh cages a core, endoderma in them generally is absent, and lateral runaways are formed endogenno, instead of put in depth, as lateral roots.

Owing to unequal activity kambija at various times year are formed unequal on size traheidy and vessels. There is the characteristic pattern, allowing to distinguish an annual gain of wood, - year rings. Them use sometimes for dating of those or other wooden subjects, and also for reception of the information on a climate during for a long time last times and about archaeological events.

The Sheet is usually flat body. Its the basic, photosynthesizing, the fabric (mefozill) is penetrated by strongly branched out veins consisting from ksilemy and floemy. The sheet is surrounded epidermisom, covered voskoobraznoj kutikuloj. Numerous ustitsa, otverstost which it is regulated turgorom closing cages, provide gas exchange between internal space of sheet and atmosphere.

Reproductive bodies (tsvetki) are not an indispensable accessory of a plant throughout all its life cycle; usually they develop in reply to defined - time-dependent year - signals of environment, such, as length of day or temperature change. In a flower man's and female bodies (stamens and plodolistiki) form the cages undergoing mejoz. Gaploidnye microdisputes develop in man's gametofity (pollen grains) in which are formed spermin; gaploidnye megadisputes in development turn in female gametofity (germinal bags), giving rise jajtsekletkam. As a result of merge spermija and jajtsekletki (fertilisations) there is a zygote and is restored diploidnoe number of chromosomes (the sexless generation - sporofit is formed). At ferns and, most likely, also at floral plants a number of stages of a reproductive cycle is under the control special chemical ' intermediaries ', or hormones.