Vegetative survival, akinete formation and germination in three blue-green algae and one green alga in relation to light intensity, temperature, heat shock and UV exposure.

The mere vegetative survival was not sufficient but suitable growth conditions were required for akinete formation to occur in the blue-green algae Anabaena iyengarii, Westiellopsis prolifica, Nostochopsis lobatus and in the green alga Pithophora oedogonia. In all algae, akinetes were neither formed nor germinated in darkness, and while dim light of 300 lx was sufficient for most of akinetes to germinate and also to maintain vegetative survival, it was not adequate for optimum akinete formation. Although akinetes of all algae could germinate at 35 degrees C, both the vegetative survival and akinete formation were markedly suppressed at this temperature. Heat or UV shock of any level, whether ineffective or effecting vegetative survival, did not promote akinete formation or germination in any alga tested. Akinetes of all algae under study were relatively tolerant to heat and also to some extent to UV. Both wet and dried akinetes of all algae were equally UV tolerant. In all algae, the viability of both wet and dried akinetes decreased more or less equally with storage time, but the decrease was more drastic when storage temperature was progressively lowered from 20 to 0 degree C. Hence the akinetes can tolerate dryness but not frost.