phytochrome


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Related to phytochrome: Cryptochrome
Phytochromeclick for a larger image
Fig. 252 Phytochrome . The photoconversion of the two forms.

phytochrome

a type of plant pigment that occurs in two forms, P660 (Pr) which absorbs red light (600–700 nm) and P725 (Pfr) which absorbs far-red light (700–760 nm). P72 5 is biologically active in that it stimulates enzymic reactions, whereas P660 is biologically inert. The conversion of one form into the other occurs simultaneously. See Fig. 252 .

Daylight contains a mixture of red and far-red light, with a predominance of red light. During the day the proportion of P725 builds up relative to P660, whereas during the night there is a gradual conversion of P725 to P660. Thus phytochrome provides the plant with a method of detecting day and night, with P72 5 predominant when it is day, and P660 predominant when it is night. This mechanism is the basis of PHOTOPERIODISM.

References in periodicals archive ?
Burial induced red-light requirement for germination, resulted in a shift from low fluence response (LFR) to very low fluence response (VLFR) of the phytochrome in A.
Phytochrome plays significant roles in germination, shoot development and branching, flowering, leaf development and other various growth and development parameters of the plants (Padem and Ozdamar, 2002).
The explanation for the shorter seedling length in the dark is the permanence of phytochrome A throughout seedling development, which inhibits etiolation, a phenomenon that only occurs in the presence of phytochrome B (Carvalho & Peres, 2013).
Red light-induced phytochrome relocation into the nucleus in Adiantum capillus-veneris.
1985), positive photoblastic seeds could be characterized by requiring a high threshold of phytochrome far-red (Pfr), to germinate, existing within the seed Pfr in an insufficient amount to start the germination process.
Rao LVM, Neeraj M, Datta M, Sudhir K, Influence of cytokinin and phytochrome on nitrate reductase activity in etiolated leaves of maize.
Natural bacterial phytochrome photoreceptors (BphPs) utilize low molecular weight biliverdin as a chromophore and provide many advantages over other chromophore binding proteins.
Potassium Channels in Samanea saman Protoplasts Controlled by Phytochrome and the Biological Clock.
Increased phytochrome B alleviates density effects on tuber yield of field potato crops, Plant Physiology, 133, 1539-1546.
The plant photoreceptor phytochrome can sense the ratio of red (660 nm) and far-red light (730 nm) in its environment.