Regulation of growth by light. How phytochrome operates?

you are: Regulation of growth by light

As in vegetative cages it is a little phytochrome and the small quantities of energy absorbed by this pigment, can cause the big physiological shifts, it is obvious that primary absorption of photons should be connected with cellular reaction by any mechanism of strengthening. Such mechanism could include management of function of genes, activity of enzymes, properties of membranes or the maintenance of such substances as the hormones, which are effective in minute quantities. All these processes, probably, take place in certain situations, but, judging by the newest data, ' the basic ' process which can result in all the rest, probably, regulation of functions of membranes is.

Ontogenetichesky reactions, such as initsiatsija flowerings, germination of seeds and deetioljatsija, undoubtedly, are connected with radical shifts in himizme, structure and function of vegetative cages. These shifts in turn depend on change of activity of many enzymes, and also from synthesis of new enzymes. As enzymes represent fibers and their synthesis is defined by translation and transcription processes, the condition fi-_ tohroma should influence or on any one of these processes, or on both. We do not know, how phytochrome carries out this influence. It could contact nuclear hromatinom, having thus direct influence on synthesis RNK and the squirrel; its influence could be and more thin, probably, connected with changes in kompartmentatsii ions in a cage and as consequence - in fiber synthesis. However the control of albuminous synthesis - not a unique way of action of phytochrome as many processes regulated by phytochrome do not depend on synthesis of fiber and are carried out too quickly.

As it is known, vegetative hormones quickly move on a plant and are effective in very small quantities. Consequences of transformations of phytochrome could be connected with synthesis or destruction of hormones or with their liberation or linkage. Apparently, any of these processes could occur quickly enough that it has allowed to explain even almost instant action of phytochrome. Synthesis or hormone splitting could be result direct fermentativnogo actions of Fdk or influence of Fdk on activity synthetic or gidroliticheskih the enzymes existing to an irradiation in a kind ' profermentov '. Linkage or liberation of hormones in places of their functioning or storage could result from updating of such places phytolame Fdk.

The Maintenance of four various hormones (gibberellinov, tsitokininov, etilena and auksina) in fabrics of the plants which have been grown up in the dark, quickly changes after a short irradiation red light whereas level of the fifth (abstsizovoj acids) changes at long influence of red light. As on gibberelliny, tsitokininy and etilen it is possible to remove influence of red light distant red light, a photoreceptor for these effects, undoubtedly, phytochrome serves. Fdk raises level gibberellinov and tsitokininov and reduces the maintenance auksina and etilena. Changes in the maintenance gibberellinov are most in details studied on etioplastah (plastidy from the fabrics which have been grown up in the dark), allocated of barley leaves. Short influence by red light after allocation causes a fast exit gibberellina from plastidy and slower increase of level of the hormone, connected, probably, with its synthesis. Fast effects, possibly, are caused by change of permeability of a membrane etioplasta. Red light or gibberellin causes in barley raskruchivanie leaves.

Numerous other fast effects of transformation of phytochrome too most likely are connected with changes in structure and function of membranes. To these effects in ' an attraction ' tips of roots of barley or masha changes concern negatively charged surface (fig. 11.17), changes in transmembrannom electric potential of cages and in ' sleepy movements ' leaves of some plants (fig. 11.18) which in turn depend on changes in movement of ions. As all these processes quickly react to a short irradiation red and distant red light, they, undoubtedly, can be result of changes of properties of membranes.

The Hypothesis that phytochrome operates ' and level of membranes, is supported also with direct demonstration of inclusion of phytochrome and its functioning in artificial lipidnyh membranes (see gl. 2). The irradiation of such membranes red and distant red light causes the big changes in their electric resistance (rice 11.19). It speaks well for that.

That konformatsionnye changes hromofora phytochrome can change simultaneously and membrane structure. Other, slower and remote effects of phytochrome, such as activation of genes and ontogeneticheskie changes, possibly, can be a consequence of this initiating event; but it is possible that phytochrome operates at once not in one direction. As we will see in the following chapter, not all reactions supervised by phytochrome are localised within one cage; in certain cases the irradiation of one part of a plant influences development of the bodies which are on some distance. The certain reactions of this kind supervised by phytochrome, occur in etiolirovannyh fabrics, but the vivid examples concern a photoperiodic induction of flowering, klubneobrazovanija and rest (see gl. 12). Any hypothesis about the mechanism of action of phytochrome should explain not only local, but also spatially remote reactions.