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A correlation between intracellular calcium and incident irradiance in Nostoc 6720
Author(s) -
SMITH R. J.,
WILKINS A.
Publication year - 1988
Publication title -
new phytologist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.742
H-Index - 244
eISSN - 1469-8137
pISSN - 0028-646X
DOI - 10.1111/j.1469-8137.1988.tb03703.x
Subject(s) - heterocyst , intracellular , biophysics , extracellular , nostoc , biology , nitrogenase , calcium , irradiance , cyanobacteria , botany , chemistry , biochemistry , anabaena , optics , bacteria , genetics , physics , nitrogen fixation , organic chemistry
SUMMARY Recent reports of Ca 2+ dependency in cyanobacterial processes, which include photosystem II, nitrogenase activity, heterocyst differentiation and trichome motility, question whether Ca 2+ ‐mediated regulation is present in these phototrophic prokaryoles. Such regulation would require that the intracellular concentration of Ca 2+ varies within an appropriate range. Several of these Ca 2+ ‐dependent processes respond to treatments which artificially alter the intracellular Ca 21+ content, but a physiological or environmental effect has not been demonstated. The effect of changes in the incident irradiance upon the proportion of heterocysts and the intracellular content of Ca 2+ in Nostoc 6720 have been investigated. Both the proportion of heterocysts (heterocyst frequency) and the cellular content of Ca 2+ (assessed by 45 Ca 24 incorporation in long labelled cultures) were negatively correlated with incident irradiance. The efflux of Ca 2+ from darkened cultures was decreased suggesting that the accumulation of intracellular Ca 2+ at low incident irradiance might result from decreased efflux. Orthovanadate, a non specific inhibitor of Ca 2+ in Anabaena variabilis , enhanced both the cellular content of Ca 24 and heterocyst frequency which suggests that direct inhibition of Ca 2+ efflux is able to mimic the effects observed on decreasing irradiance.