Competing interactions with other members of vegetative community. fitoaleksiny

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Fitoaleksiny are the antimushroom connections formed in a plant in reply to its infection by a mushroom. The name ' fitoaleksiny ', meaning in a translation from Greek ' averting substances ', was fixed in a science when researchers incorrectly believed, as if in similar substances the immune answer of a plant, equivalent to the immune answer of animals is shown. Actually in these substances not so specific answer on mushroom invaziju, and a certain general answer - on any damage is shown.

Now from a wide range of plants variety of connections of this type is allocated. On the chemical structure they have appeared very various. Each of them, apparently, is specific to that plant in which it is formed, the formation way depends by nature given fitoaleksina. So, for formation pizatina (fig. 15.8), peas developed in plants, is not required special changes in a metabolism of vegetative fabrics, because from representatives of family Leguminosae to which peas, widespread izoflavonoidy, on the structure close to pizatinu belong. Obviously, pizatin it is formed of amino acid fenilalanina which thus at first dezaminiruetsja under action fenilalanin-ammiakliazy with formation of cinnamon acid, and is a way, the general for all flavonoidov.

Whether Can given fitoaleksin to inform a plant stability, it depends on many factors. Extremely important, how fast the plant is distinguished by the infectious agent and reacts to it. Quite often fitoaleksin it starts to be developed after infection too late when the mushroom already has had time to extend on a fabric. In other cases it appears that the mushroom possesses ability to decompose given fitoaleksin and thanks to it also extends. Mushroom Botrytis cinerea is sensitive to fitoaleksinu horse beans (Vicia faba) and consequently is limited in the distribution by an infection place so on leaves it causes only occurrence of small brown specks (whence and the name of this illness - ' chocolate pjatnistost '). The related kind of a mushroom, Botrytis fabae, destroys this fitoaleksin that allows it to extend on all sheet.

On an example antraknoza (Phaseolus vulgaris) which activator is mushroom Cotletotrichum lindemuthianum, it is possible to show to a string bean the interrelations existing between a plant-owner, a mushroom infection and formation fitoaleksinov. Stability or a susceptibility of various grades of a string bean to this illness do not manage to be connected with the strengthened formation fitoaleksina fazeolina (fig. 15.8 see) which is observed at them later 24 ch after artificial infection of plants. Plants of a steady grade answer introduction of a mushroom by immediate  destruction of a cage-owner so rostkovaja the tube of the mushroom which has formed on a surface of a cage spherical apressory, to get is deeper cannot any more. The mushroom in plants of susceptible grades otherwise behaves: rostkovaja the tube sprouts here through a wall of a cage-owner and continues to grow between this cellular wall and a protolayer, without causing a cage of essential damages. Thus mushroom floccuses grow throughout several days, extending from a cage to a cage, still without special traces of damage. Then typical symptoms antrak-noza are suddenly shown: poburenie, nekrozy and  destruction of fabrics. At a steady plant fast formation fazeolina begins for the second day after infection, simultaneously with the advent of the small brown specks testifying to supersensitivity. At a susceptible plant fazeolin it is not developed until on leaves will not appear typical antraknoznye defeats, and at this time fitoaleksin to help cannot any more! We see, in such a manner that though this fitoaleksin, apparently, and is capable to serve its purpose in the illness prevention, essential distinction between steady and susceptible grades is defined by their ability to distinguish patogena and in appropriate way to react. And on the contrary, specificity of illness, obviously, can depend on, whether the given race is capable patogena to avoid damage of cages (i.e. Not to provoke leaders to it processes or to suppress them) and such way to avoid plant response - formations fitoaleksinov. Probably, hence, that supersensitivity reaction is one of the main reactions, providing to a plant stability to mushroom invazii. At supersensitivity the infected fabric quickly dies off, and is frequent and sites of a fabric adjoining it so a mushroom, it having appeared in isolation among dead cages to infect other cages of a plant cannot any more. Now this most interesting phenomenon is strenuously studied.