Determination of generation time and growth curve of Nostoc muscorum and Nostoc ellipsosporum by measuring of chlorophyll in modified Allen's medium

Diazotrophic cyanobacteria, which are nearly found everywhere, have important role in N fixation and play a vital role in improving and establishing the soils. Little studies have been carried out on the life cycle of heterocystous cyanobacteria in paddy fields of Iran. Sampling, purification and identification of cyanobacteria from paddy fields of Golestan province was carried out and showed that Nostoc ellipsosporum and N.muscorum are the most abundant species of the sites. To draw the growth curves of the species each was grown on Allen culture medium separately and their growth curves were drawn according to their chlorophyll amounts. Doubling time of each species was also calculated based on the chlorophyll data. The results showed that N.ellipsosporum has longer doubling time and logarithmic phase than N.muscorum. Hence, it can have longer activity and fix more N in the ecosystem.