Metalaxyl effect on nitrogenase activity (acetylene reduction) and yield of mungbean (Vigna radiata (L.) wilzek).

In an experiment, application of different levels of metalaxyl to a sandy loam soil significantly affected the nodulation and nitrogenase activity of mungbean. In both the compost amended and unamended soils, 0.5 mg kg(-1) of metalaxyl enhanced acetylene reduction activity and yield of mungbean, where as higher concentrations (1 mg and 2.5 mg kg(-1) of fungicide) inhibited the nodulation traits as well as economic traits of mungbean.

Effect of lead on nitrogenase and enzymes of nitrogen assimilation in a cyanobacterium Nostoc muscorum.

Lead decreased the growth rates, total cell mass, heterocyst frequency, total cell protein, nitrogenase activity, glutamine synthetase (GS) and glutamate synthase (GOGAT) activities in N:muscorum. However, lead at 0.01 and 10 micrograms ml-1 conc. enhanced nitrogenase as well as GS activity of the cells. On transfer to excess lead (100 micrograms ml-1), nitrogenase and GS activities ceased almost after 24 hr in the cyanobacterium. It is deduced that lead has a two step effect on stimulation and inhibition of metabolic activity at 0.01 and 10 micrograms ml-1 concentration and 0.1 and 100 micrograms ml-1 concentration respectively indicating a close interaction between nitrogen fixation and GS activity. However, GOGAT activity is an exception to this two step stimulation and inhibition process.

Interactive effects of molybdenum and vanadium on the nitrogenase and nitrate reductase activities of aulosira fertilissima

The effects of molybdenum and vanadium interactions on the nitrogenase and nitrate reductase enzymatic systems in the cyano-bacterium Aulosira fertilissima were investigated at different time intervals. Addition.of Va to + Mo cultures up to 0.015 ppm increased both dry weight gain and pigment biosynthesis. Beyond this concentration significant inactivation of such enzymes was observed at all growth periods. Nitrogenase and nitrate reductase activities were significantly increased by addition of Va at different levels to the cultures augmented with Mo, a phenomenon that was reversed by increasing Va concentrations. Maximum nitrogenase activity was recorded after 48 hr of incubation, whereas the highest enzymatic potential was maintained after 96 hr incubation period. Nitrogenase and nitrate reductase activities in + Mo cultures were significantly higher than in -Mo cultures. Addition of Va to + Mo Aulosira cultures resulted in a marked elevation in heterocyst frequency particularly after 48 hr incubation