Influence of Environmental Stress on the Germination of Anabaena vaginicola Akinetes

Abstract

Germination of akinetes of Anabeana vaginicola v. fertilissima Prasad in response to environmental stress was studied. Addition of nitrate to the medium induced early and maximum germination (96 per cent), whereas less than half of the akinetes germinated when either nitrate or phosphate was omitted from the medium. The pH range over which germination occurred was 7 0-9 0. The desiccated akinetes after rehydration germinated after a certain lag period, depending upon the dehydration state. The temperature optimum for germination and vegetative growth was the same (25 °C) and germination did not occur at 5 °C or above 35 °C. The limit of heat shock tolerated was 55 °C for 4 min. In addition to white light, only the red part of the visible spectrum induced germination. Ultraviolet radiation reduced germination rate presumably by inducing thymine dimers in DNA. The photoreactivating system(s) in akinetes is certainly non-photosynthetic. LD50 photon flux densities were 300 J m~2 for akinetes and 240 J m~2 for vegetative cells.