Section 6
Chapter 5,987

Nitrogen fixation by nodularia spumigena cyanobacteriaceae 2. laboratory studies

Huber, A.L.

Hydrobiologia 133(3): 193-202


ISSN/ISBN: 0018-8158
DOI: 10.1007/bf00005590
Accession: 005986475

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The effects of changes in diurnal light patterns, salinity, and phosphorus on nitrogen fixation (as measured by acetylene reduction) by Nodularia spumigena Mertens were examined. As well, the effects of added inorganic nitrogen on growth, nitrogen fixation and heterocyt frequencies, and changes in nitrogen fixation and heterocyst frequencies during the growth cycle of Nodularia in cultures were determined. The diurnal pattern of nitrogenase activity in Nodularia was primarily light-induced, though dark activity did occur. Nitrogenase activity following a period of darkness exceeded the normal light rate (>90 compared to 50 nmol .cntdot. C2H2 reduced .cntdot. ml-1 .cntdot. h-1). Nitrogen fixation was reduced by high and very low salinities (5 to 10.permill. was the optimum range), and added phosphorus stimulated nitrogenase in P-starved cells. Added nitrogen (ammonium or nitrate) had no effect on the growth of Nodularia, but in short term studies, ammonium completely inhibited nitrogenase activity. Heterocyst frequencies were greatest in the log phase of growth (to 40 per mm). During stationary phase, nitrogenase activity was negligible.

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