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GROWTH RESPONSE OF A NITROGEN FIXER ( ANABAENA FLOS‐AQUAE , CYANOPHYCEAE) TO LOW NITRATE 1
Author(s) -
Elder Robert G.,
Parker Michael
Publication year - 1984
Publication title -
journal of phycology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.85
H-Index - 127
eISSN - 1529-8817
pISSN - 0022-3646
DOI - 10.1111/j.0022-3646.1984.00296.x
Subject(s) - biology , dilution , nitrogen fixation , zoology , nitrate , nitrogen , growth rate , cyanobacteria , botany , anabaena , nutrient , nitrogenase , photosynthesis , food science , ecology , chemistry , physics , genetics , geometry , mathematics , organic chemistry , bacteria , thermodynamics
Anabaena flos‐aquae (Lyngb.) Bréb. was grown in varying concentrations of nitrate. Specific growth rates, as estimated in batch culture, were constant and approached the maximum rate at all concentrations of NO 3 − ‐N tested bewteen 0 and 400 μ/L. Steady‐state biomass, as determined in semicontinuous culture, did not vary with NO 3 − at slower dilution rates. However at a faster dilution rate, significantly less biomass occurred in intermediate concentrations of NO 3 − than in either higher or lower concentrations. The results indicate that both growth rate and standing crop are maximized by either N 2 fixation or NO 3 − assimilation, but extracellular NO 3 − reduces the rate of N 2 fixation. Consequently, at very low NO 3 − concentrations, growth is virtually maximized by N 2 fixation alone, and at high concentrations of NO 3 − , N 2 fixation is inhibited but growth is maximized by assimilation of NO 3 − . At intermediate concentrations of NO 3 − , growth becomes a function of NO 3 − assimilation augmented by N 2 fixation. In this case, full growth potential is realized only if hydraulic residence time is sufficiently long to compensate for the reduced rate of N 2 fixation. Growth rate and standing crop are not diminished in response to the large amount of energy allocated to N 2 fixation. Instead, other cellular processes are probably affected negatively during N 2 fixation.