Nitrogen fixation by Aulosira fertilissima in rice fields

Abstract

Mats of Aulosira fertilissima in rice fields of Varanasi showed a diurnal pattern of acetylene reduction. In situ short term assays gave high amounts of acetylene reduction activity in daylight and reduced rates in the dark. This dark fixation rate was about 31% of the total acetylene reduced. Cultures of A. fertilissima when exposed to the same natural conditions gave acetylene reduction rates less than of mats. Combined nitrogen sources present in the rice field soil and no inhibitory effects on acetylene reduction rates when supplied in same amounts to laboratory grown A. fertilissima cultures. Substantial acetylene reduction activity at 24 hrs suggests that the organisms is capable of reducing acetylene during the night hours.