THE LIGHT PROMOTED GERMINATION OF THE SEEDS OF CHENOPODIUM ALBUM L. IV. EFFECTS OF RED, FAR-RED AND WHITE LIGHT ON NON-PHOTOBLASTIC SEEDS INCUBATED IN MANNITOL

Abstract

The effects of red, far-red and white fluorescent light on the germination of dark germinating seeds of Chenopodium album, incubated in a range of mannitol concentrations, have shown that the far-red absorbing form of phytochrome (Pfr) is present in these seeds. The requirement of the germination processes for Pfr increased, when the osmotic concentration of the incubation medium was increased. It is concluded that this requirement for Pfr depends on the position of a balance between promotive and inhibitory factors. Pfr influences this balance in a positive direction. It was shown that osmotic stress, a thick seed-coat and (RS)-abscisic acid can function as inhibitory factors. In its influence on the last stage of the visible germination phenomena (the protrusion through the inner seed-coat layer) white light resembles in lower osmotic concentrations red light, in higher concentrations it resembles far-red light. The earlier stages (elongation inside the seed) are influenced, in all tested concentrations, similar by red and white light. It is assumed that during the last phase of the germination process “seedling phytochrome” instead of “seed phytochrome” has a regulatory function.