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NITRATE REDUCTASE ACTIVITY OF AMPHIDINIUM CARTERI AND CACHONINA NIEI (DINOPHYCEAE) IN BATCH CULTURE: DIEL PERIODICITY AND EFFECTS OF LIGHT INTENSITY AND AMMONIA 1, 2
Author(s) -
Hersey Ronald L.,
Swift Elijah
Publication year - 1976
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.1529-8817.1976.tb02823.x
Subject(s) - nitrate reductase , enzyme assay , diel vertical migration , biology , enzyme , light intensity , reductase , dinophyceae , nitrate , ammonium , ammonia , biochemistry , botany , nuclear chemistry , chemistry , ecology , nutrient , physics , phytoplankton , optics , organic chemistry
SUMMARY The activity of extracted NADH‐NO 3 − reductase was measured in the marine dinoflagellates Amphidinium carteri Hulburt and Cachonina niei Loeblich. Its activity showed a diel periodicity and was ca. twice as great at midday as at midnight. The enzyme activity was unstable, with an in vitro half‐life of 2–3 h. Values of enzyme activity were low or undetectable during lag phase but paralleled the instantaneous growth rate value during log phase. Nitrate reductase activity was not found in the stationary phase of growth, but additions of NO 3 − resulted in enzyme activity after 24h. When A. carteri was exposed to a series of light intensities for several weeks, the division rate and enzyme activity increased with increasing light intensity up to saturating intensities. In 6 h exposures, enzyme activity decreased with decreasing light intensities below light intensities saturating division rate. Additions of NH 4 + (0.5–50 μm) to A. carteri cultures decreased the amount of extractable enzyme. The in vitro activity was not inhibited by similar NH + 4 concentrations.