Interplay of Calcium and Nitric Oxide in improvement of Growth and Arsenic-induced Toxicity in Mustard Seedlings

In this study, Ca(2+) mediated NO signalling was studied in response to metalloid (As) stress in Brassica seedlings. Arsenic toxicity strongly suppressed the growth (fresh weight, root and shoot length), photosynthetic pigments, Chl a fluorescence indices (Kinetic traits: F(v), F(m), F(v)/F(o), F(m)/F(o), ФP(o) or F(v)/F(m), Ψ(o), ФE(o), PI(ABS), Area and N and redox status (AsA/DHA and GSH/GSSG ratios) of the cell; whereas energy flux traits: ABS/RC, TR(o)/RC, ET(o)/RC and DI(o)/RC along with F(o), F(o)/F(v), F(o)/F(m), ФD(o) and S(m)) were enhanced. Further, addition of EGTA (Ca(2+) scavenger) and LaCl(3) (plasma membrane Ca(2+) channel blocker) to As + Ca; while c‒PTIO (NO scavenger) and l‒NAME (NO synthase inhibitor) to As + SNP treated seedlings, siezed recovery on above parameters caused due to Ca(2+) and NO supplementation, respectively to As stressed seedlings thereby indicating their signalling behaviour. Further, to investigate the link between Ca(2+) and NO, when c‒PTIO and l‒NAME individually as well as in combination were supplemented to As + Ca treated seedlings; a sharp inhibition in above mentioned traits was observed even in presence of Ca(2+), thereby signifying that NO plays crucial role in Ca(2+) mediated signalling. In addition, As accumulation, ROS and their indices, antioxidant system, NO accumulation and thiol compounds were also studied that showed varied results.