Conclusion
From the present study, the conclusion could be drawn that Ni2+ inhibits overall growth of nitrogen fixingAnabaena cells; while SA, CaCl2 and SNP addition significantly recovered the growth and growth regulating processes (Fig. 8). However, upon supplementation of NO (c-PTIO) or/ and Ca2+ (EGTA) scavenger to Ni+SA+Ca, Ni+SA+NO or Ni+SA stressed Anabaena cells, the improvement in growth caused by SA, Ca2+ and NO was further arrested, which suggests that Ca2+ and NO both are the part of SA induced signaling event. But the steep decline in growth and growth regulating attributes: EPS secretion, pigments, photosynthetic rate, nitrogen metabolism status and antioxidants system was mainly observed under Ni+SA+Ca+c-PTIO than that of Ni+SA+NO+EGTA treatment even in presence of SA, thereby suggesting that SA induced positive impact on physiological and biochemical traits of Anabaena cells are mostly regulated by Ca2+ mediated NO signaling (Fig. 8).