Polarotropism and Photomovement of Chloroplasts in the Protonemata of the Ferns Pteris and Adiantum: Evidence for the Possible Lack of Dichroic Phytochrome in Pteris

The actions of red and blue light in the photomovement of chloroplastsand the polarotropic response were studied in the protonemataof the homosporous ferns Pteris vittata L. and Adiantum capillus-venerisL. In Pteris, polarotropism could be induced with blue lightbut not with red light, while both colors of light were effectivein Adiantum protonemata. The photomovement of chloroplasts inthe two species studied by both polarized light and microbeamirradiation, also revealed similar responses to red and bluelight as the polarotropism; i.e. both colors of light were effectivein Adiantum but only blue light was active in Pteris. The resultsin Adiantum were consistent with previous results, which ledto the conclusion that both phytochrome and a blue light-absorbingpigment are involved in the two responses (Kadota et al. 1982,1984, Hayami et al. 1986, Yatsuhashi et al. 1985). By contrast,phytochrome is not involved in either polarotropism or chloroplastmovement in Pteris. Since the phytochrome system is evidentlyactive in every other photoresponses so far investigated inPteris as well as in Adiantum, the present study suggests thata phytochrome system specific to polarotropism and to photomovementof chloroplasts is absent in Pteris. Discussions are presentedon the possible involvement of two phytochrome populations ina fern gametophyte cell and on the possible lack of dichroicphytochrome in Pteris. (Received October 7, 1988; Accepted March 8, 1989)