A new light-induced absorbance change having a maximum at 561 nm was discovered in the thalli, as well as in isolated chloroplasts of a green alga,Bryopsis maximaOkamura.Another simultaneous change also occurred at 515 nm. The magnitude of the 561 nm change was several-fold larger than that at 515 nm and much larger than could be explained by an oxidation-reduction change in cytochromes contained in chloroplasts. There was no absorbance change in the Soret region that may be correlated to the 561 nm change. Both 561 and 515 nm changes showed a spike-like time course pattern, both having a half-rise time of about 20 msec. Effects of inhibitors and uncouplers such as DCMU, Cl-CCP and gramicidin J on the absorbance change were also similar at 561 and at 515 nm.We inferred that the 561 nm change is related to photophosphorylation and possibly to the membrane potential in a way similar to the 515 nm change.
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