Studies On Culture Of The Terrestrial Blue-green Alga, Nostoc Flagelliforme

In order to develop the technique for cultivation and restoring the endangeredresources of the terrestrial blue-green alga, Nostoc flagelliforme, its colonies and free-living cells were cultured under aquatic conditions. Unicellular and colonial filaments obtained from the aquatic culture were further cultivated under aerated conditions. Morphological changes and growth during the cultures were examined.Under submerged aquatic conditions, the colonial filaments disintegrated with their sheaths ruptured in about 2 days without any desiccating treatments. Periodic desiccation played an important role in preventing the alga from being decomposed, delaying the sheath rupture to later days with higher frequencies of exposure to air for desiccation. Bacteria number in the culture treated with 7 times of desiccation per day was about 50% less compared with the cultures without the treatment. When the bacteria in culture was controlled, the colonial filaments did not disintegrate in short time, and maintained the integrity of their sheath for about 20 days even without the desiccation treatments, indicating the importance of desiccation for N. flagelliforme to keep from being disintegrated by bacteria.On the other hand, free-living cells were obtained by crushing the rehydrated colonial filaments. They were cultured in liquid medium under different light and temperature conditions, and their morphology and growth were investigated. Thefree-living cells developed to unicellular filaments with sheaths, within which multiple filaments were formed later on as a colony. Such colonial filaments were developed at 15, 25 and 30, at either 20 or 60 except 180 umolrrfV, though such a high light level resulted in the highest growth of the cells. A condition of 60 nmolm'V and 25 appeared to result in best colonial development and faster growth of the sheath-held colonies of N. flagelliforme when cultured indoor under aquatic conditions.The unicellular and colonial filaments with sheath resulted from the above cultures were shifted to and cultured on a solid agar medium exposed to air. Watering was conducted with different frequencies, low (2 times day1), intermediate (4 times day1), and high (8 times day1). The watering amount was 160 ul/cm2 every times. The unicells died in three days even under the highest watering frequency due to desiccation. Under moderate watering conditions, the morphological development of the colonial filaments with sheath was better than under low or high watering frequency. The filaments grew to about 2 mm in the first two months. Color of the filaments changed with time in air from blue to yellowish, then to yellow-brown, and later to dark-brown, being close to the natural color of N. flagelliforme. While under high watering frequency condition, the filaments were disintegrated in six days probably due to high bacteria propagation.