Some Physiological Responses of Nostoc sp. JAH 109 to the Combination Effects of Limited Irradiance, pH and DIC Availability

Growth, pigment compositions, nitrogenase activity, photosynthesis and heterosyct frequency fluctuations of dominant species Nostoc sp. JAH 109, isolated from rice field, were evaluated in combination of limited irradiance (2 uE.m-2.s-1), different pHs (5,7,9) and inorganic carbon availability. Nostoc sp. JAH 109, can be considered as an alkalophilic organism. Optimal growth rate were observed at pH 9. Size of phycobilisomes and relationship between photosystem II and photosystem I increased in pH 9 and DIC available condition. This strain could not grow well in acidic condition, but neutral and alkaline condition cause active carbon dioxide concentration mechanism system. The pattern of nitrogenase activity seems more or less regular and linear at the first days after inoculation both in neutral and alkaline conditions. With respect to nitrogenase activity, the highest rate was in pH 9 and DIC availability. This seems true for heterocyst frequency fluctuations too. The higher photosynthetic capacity (Pmax) per unit of chlorophyll was resulted in higher DIC concentration at alkaline condition.