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.

Collins Dictionary of Biology, 3rd ed. © W. G. Hale, V. A. Saunders, J. P. Margham 2005
References in periodicals archive ?
stans also presents phytochrome B (PhyB), which has been associated with the detection of forest gaps through changes in the R:FR ratio (Smith, 1995).
Cryptochrome, phytochrome, and anthocyanin production.
Previous studies have confirmed that the seeds depend on phytochrome, perceiving the surrounding environment and respond through the optical signal pathway (Dooley et al., 2013).
Abe, "Genetic redundancy in soybean photoresponses associated with duplication of the phytochrome A gene," Genetics, vol.
There are reports indicating the role of light detector Phytochrome B and HDA6 in regulating light-controlled chromatin of Nuclear Organization Regions (NORs) [23].
Phylogeny of the parasitic family Orobanchaceae inferred from phytochrome A.
Control of mitosis by phytochrome and a blue-light receptor in fern spores.