Regulation of growth by light. Properties of phytochrome

you are: Regulation of growth by light

The phytochrome Molecule consists of two parts: concerning small hromofora, absorbing light, and much larger colourless fiber. Hromofor, similarly hromoforu fikotsianina and other pigments of seaweed, represents tetrapirrol with not closed chain. after absorption by phytochrome of light with certain length of a wave the form hromofora changes, and it in turn changes the form of an albuminous component. Fiber, apparently, consists from 4 subedinits, located in the form of a double dumbbell, with the general a pier. In weight nearby 240 000; it is moderately large fiber consisting approximately from 2000 amino acids.

Prevrashchenie Fk in Fdk at short-term influence of red light influences biochemical reactions in a plant within several next hours darkness. This amazing firmness of effect of so short irradiation depends that Fdk, being ' active ' the phytochrome form, is rather stable in the dark. at 25 °s the period of a semilife of Fdk in etiolirovannoj usually makes fabrics nearby 2 ch (i.e. For 2 ch the maintenance of Fdk decreases to half of its initial quantity), and in a fabric growing on light, this period, possibly, reaches 8-12 ch. In some experiences with fabrics growing on light activity of Fdk can be found out after more 72 ch after an irradiation red light. Unlike it the activated forms of other vegetative pigments are very astable; at the raised chlorophyll, for example, the semilife period makes only some milliseconds.

Slow decrease in level of Fdk in the dark after an irradiation red light is caused by two processes-reversiej and destruction. In one fabrics of Fdk in the dark slowly turns in Fk; in other fabrics after transformation of Fk into Fdk the general maintenance of phytochrome decreases (i.e. The pigment collapses). In certain cases both processes occur simultaneously. destruction of phytochrome and reversija Fdk in Fk are accelerated at heats, and speeds of these processes vary in different plants and in the same plant at growth in different conditions. As we will see in gl. 12, in seeds thermal reversija Fdk in Fk plays the important role in germination regulation.