Flavin-Mediated Weak-Light Chloroplast Movement in Mougeotia

Abstract

In Mougeotia the two types of chloroplast movement depend in a different way on the wavelength of the orienting light: The high-fluence-rate response (face-to-profile orientation) can be induced exclusively by blue light, and this is an effect of an interaction of phytochrome and a blue-light-absorbing pigment (cf. [10]). In contrast, the low- fluence-rate response (profile-to-face orientation) has its maximum in red light with a typical red/far-red reversibility; thus, phytochrome has been accepted as the main photoreceptor pigment involved ([4], cf. also [5]). There was, however, some controversy, whether or not the lower effect of the blue light region could be explained on the basis of phytochrome alone (e.g. [3], cf. also [5]). Only recently a strong argument in favor of a separate blue-light photoreceptor pigment has been derived from a new experimental approach [2]. These results will be summarized briefly, and additional experiments will be reported.