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The Light Requirement for Different Steps in the Development of Chloroplasts in Excised Wheat Roots
Author(s) -
Björn L. O.
Publication year - 1967
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/j.1399-3054.1967.tb07189.x
Subject(s) - phytochrome , blue light , action spectrum , chloroplast , red light , pigment , biophysics , photosynthesis , chemistry , botany , biology , photochemistry , optics , biochemistry , physics , organic chemistry , gene
For the formation of chloroplasts in excised wheat roots blue light is necessary, but red light enhances the blue light effect. Intensity‐response relationships and action spectra have been determined for the specific blue light effect as well as for the effect of red light when given before or after blue light. The longest wave length giving a blue light effect is about 500 nm. The spectrum shows a peak at about 450 nm, and a considerable effect extends down to 368 nm, the shortest wave length tested. The photoreceptor mechanism for the “blue reaction” is thought to be related to that of certain phototropisms and chloroplast movements, and to that involved in carotenoid synthesis in certain fungi. The active pigment is thought to be either a carotenoid or a flavoprotein, probably the latter. The effect of red light shows similar action spectra whether the red light is given before or after the blue, and they are consistent with protochlorophyll absorption. However, much less light is needed to produce a detectable response when the red light is given before the blue light than after. Because of the similarity of the spectra phytochrome may also be involved in the response to red light when given before blue. Far‐red reversal has not been tested. The results are discussed in relation to the development of chloroplasts in leaves.