Photoreversible and photoirreversible absorbance changes in the red and far-red spectral regions inZeaprimary roots

摘要

When 2-mm apical segments of the primary roots ofZea maysL. (cv. Golden Cross Bantam 70) were irradiated successively with red and far-red light, a photoirreversible absorbance decrease was separated from the red far-red reversible absorbance change typical of phytochrome. The difference spectrum of the reversible change showed maximum absorbance changes at 666 and 730 nm, while the photoirreversible change induced by red light showed a maximum decrease at 640 nm. The photoreversible absorbance change was linearly proportional to the fluence of red light between 1 and 6 J m−2, while the photoirreversible absorbance change was proportional to its logarithm. Red light of approximately 6 J m−2induced 50of the maximum photoirreversible absorbance change at 640 nm but only about 25of the maximum photoreversible absorbance change. Moreover, no effect of ascorbate on the two absorbance changes was obser