Brief irradiation with red or blue light induces orientational movement of chloroplasts in dark-adapted prothallial cells of the fernAdiantum

Abstract

Orientational movement of chloroplasts was induced by a brief irradiation with red light (R) or blue light (B) in dark-adapted prothallial cells ofAdiantum, whose chloroplasts had gathered along the cell dividing wall (i.e., the anticlinal wall). When the whole dark-adapted prothallia were irradiated from a horizontal direction (i.e., from their lobes) with horizontally vibrating polarized R (H pol. R) for 10 or 3 min, the chloroplast left the anticlinal walls and spread over the prothallial surface (i.e., the periclinal walls) within 1–2 hr after the onset of irradiation, returning to the anticlinal wall (dark-position) within 10 hr. However, vertically vibrating polarized R (V pol. R) for 10 min did not induce the movement towards periclinal walls. The R effect was cancelled by non-polarized far-red light (FR) irradiation just after the R irradiation. Irradiation with H pol. B for 10 or 3 min but not with V pol. B could also induce a similar movement of chloroplasts, although the chloroplasts returned within 4 hr. The effect of H pol. B, however, was not cancelled by the subsequent FR irradiation.

When a part of the dark-adapted cell at the prothallial surface was irradiated from above with a microbeam of R or B for 1 min, chloroplasts of the cell in the dark-position moved towards the irradiated locus in subsequent darkness. However, in the neighboring cells, orientational movement was not induced by either R or B microbeams.

These results show that in dark-adapted prothallial cells, both brief irradiation with R and B can induce chloroplast photo-orientation and that the photoreceptors are phytochrome and blue light-absorbing pigment, respectively. It is also clear that effects of both R and B irradiation do not transfer to neighboring cells.