Influence of light, temperature and nitrogen on morphogenesis of Desmotrichum undulatum (J. Agardh) Reinke (Phaeophyta, Punctariaceae)

Abstract

The initial filamentous system produced by spores from plurilocular sporangia of Desmotrichum may bear erect blades, colourless hairs and plurilocular sporangia. Production of each of these organs is influenced by environmental factors. In the present study, Desmotrichum undulatum from Massachusetts was grown under fifteen temperature/photo-period combinations, and in continuous white, blue and red light in various culture media. Plants formed plurilocular sporangia at 20, 15 and 10°C in all photoperiods, and even at 5°C in long-day conditions. Erect blades were formed at 5, 10 and 15°C in all photoperiods. At 20°C, no blades were formed in short-day, but 100% of the plants formed blades in long-day. Blade formation in long-day at 20°C is not interpreted as a true photoperiodic response, since insertion of a light break in the middle of the long dark period did not reverse the inhibitory effect of short-day. Morphogenetic effects of light quality also are found in Desmotrichum. Release of spores from the plurilocular sporangia requires blue light. Light quality also affects hair formation in Desmotrichum, but only when ammonium is present in the culture medium.