Phytohormone up-regulates the biochemical constituent, exopolysaccharide and nitrogen metabolism in paddy-field cyanobacteria exposed to chromium stress

Abstract Current study deals with the assuaging effects of two phytohormones; indole acetic acid (IAA; 290 nM) and kinetin (KN; 10 nM) on growth, phycobiliproteins, status of nitrogen metabolism and biochemical constituents; protein, carbohydrate and exopolysaccharide contents in two diazotrophic cyanobacteria Nostoc muscorum and Anabaena exposed to chromium (CrVI) stress (100 µM and 150 µM). Chromium individually at both the tested doses expressively declined the growth, chlorophyll a to carotenoid ratio and contents of phycobiliproteins; phycocyanin (PC), allophycocyanin (APC), and phycoerythrin (PE). With distinctive impact on status of nitrogen metabolism chromium significantly reduced the nitrate (NO3—) and nitrite (NO2—) uptake rate and foremost decrease in nitrate and ammonia assimilating enzyme; nitrate reductase (NR), nitrite reductase (NiR), glutamine synthetase (GS), glutamate synthase (GOGAT) except glutamate dehydrogenase (GDH). However, beneath alike condition, exogenous application of IAA and KN exhibited noteworthy assuaging effects on growth-regulating parameters in both the paddy field cyanobacteria, which consummately occurred as a result of substantial decrease in Cr uptake and inducing signaling responses and also enhances the growth parameter i.e. nitrogen metabolism as a result of considerable lowering in Cr induced damaging effect on nitrogen metabolism and uptake rate, and the alleviating effect was more pronounced with the lower dose of Cr, efficient in N.muscorum than Anabaena.</jats:p

Phytohormone up-regulates the biochemical constituent, exopolysaccharide and nitrogen metabolism in paddy-field cyanobacteria exposed to chromium stress

Abstract The authors have withdrawn the journal submission associated with this preprint and requested that the preprint also be withdrawn.</jats:p

Phytohormone up-regulates the biochemical constituent, exopolysaccharide and nitrogen metabolism in paddy-field cyanobacteria exposed to chromium stress

Abstract Background Cyanobacteria are well known for their inherent ability to serve as atmospheric nitrogen fixers and as bio-fertilizers; however, increased contaminants in aquatic ecosystem significantly decline the growth and function of these microbes in paddy fields. Plant growth regulators play beneficial role in combating the negative effects induced by heavy metals in photoautotroph. Current study evaluates the potential role of indole acetic acid (IAA; 290 nm) and kinetin (KN; 10 nm) on growth, nitrogen metabolism and biochemical constituents of two paddy field cyanobacteria Nostoc muscorum ATCC 27893 and Anabaena sp. PCC 7120 exposed to two concentrations of chromium (CrVI; 100 μM and 150 μM). Results Both the tested doses of CrVI declined the growth, ratio of chlorophyll a to carotenoids (Chl a/Car), contents of phycobiliproteins; phycocyanin (PC), allophycocyanin (APC), and phycoerythrin (PE), protein and carbohydrate associated with decrease in the inorganic nitrogen (nitrate; NO3— and nitrite; NO2—) uptake rate that results in the decrease in nitrate and ammonia assimilating enzymes; nitrate reductase (NR), nitrite reductase (NiR), glutamine synthetase (GS), glutamate synthase (GOGAT) except glutamate dehydrogenase (GDH). However, exogenous supplementation of IAA and KN exhibited alleviating effects on growth, nitrogen metabolism and exopolysaccharide (EPS) (first protective barrier against metal toxicity) contents in both the cyanobacteria, which probably occurred as a result of a substantial decrease in the Cr uptake that lowers the damaging effects. Conclusion Overall result of the present study signifies affirmative role of the phytohormone in minimizing the toxic effects induced by chromium by stimulating the growth of cyanobacteria thereby enhancing its ability as bio-fertilizer that improved fertility and productivity of soil even in metal contaminated condition. </jats:sec