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

In this study, Ca2+ 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, ?P-o or F-v/F-m, Psi (o), ?E-o, PIABS, Area and N and redox status (AsA/DHA and GSH/GSSG ratios) of the cell; whereas energy flux traits: ABS/RC, TRo/RC, ETo/RC and DIo/RC along with F-o, F-o/F-v, F-o/F-m, ?D-o and S-m) were enhanced. Further, addition of EGTA (Ca2+ scavenger) and LaCl3 (plasma membrane Ca2+ channel blocker) to As+Ca; while cPTIO (NO scavenger) and lNAME (NO synthase inhibitor) to As+SNP treated seedlings, siezed recovery on above parameters caused due to Ca2+ and NO supplementation, respectively to As stressed seedlings thereby indicating their signalling behaviour. Further, to investigate the link between Ca2+ and NO, when cPTIO and lNAME 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 Ca2+, thereby signifying that NO plays crucial role in Ca2+ mediated signalling. In addition, As accumulation, ROS and their indices, antioxidant system, NO accumulation and thiol compounds were also studied that showed varied results.