Growth and special structures production of Nostoc paludosum (Nostocaceae, Cyanobacteria) under nutrient starvation and different light intensities

Crescimento e produção de estruturas especiais em Nostoc palusodum (Nostocaceae, Cyanobacteria) sob limitação nutricional e diferentes intensidades luminosas

Abstract

The effects of the absence of nitrogen and phosphorus on AA media and three different light intensities (100% Light, 60.0 ± 2.7 μmol m^-2 s^-1, 50% Light, 30.0 ± 2.7 μmol m^-2 s^-1, and 13.5% Light, 8.1 ± 2.7 μmol m^-2 s^-1) on cell production and synthesis of heterocytes and akinetes were determined in a strain of Nostoc paludosum. In the experiment concerning the absence of nutrients, significant variations were observed between the control group and the groups with absence of nutrients, especially in cell numbers and in synthesis of heterocytes and akinetes. The absence of nitrogen boosted the formation of heterocytes and the absence of phosphorus produced the most akinetes. As for the different light conditions, the growth curves determined for each treatment showed that cell synthesis is slightly affected by the reduction of illuminance. The different light intensities are capable of reducing the maximum growth rates of Nostoc paludosum, with 13.5% light restriction being the most effective on limiting the cell growth rate and inducing the formation of akinetes. The synthesis of heterocyte does not seem directly correlated to light intensity, being better explained by nutritional factors. The data found contributes to the understanding of some of the factors involving growth and synthesis of special structures in Nostoc paludosum.

Keywords:
Limnology; microbiology; nostocales.