Photosynthetic activity and RAPD profile of polyethylene glycol treated B. juncea L. under nitric oxide and abscisic acid application.

The involvement of two extremely important signalling molecules, nitric oxide (NO) and abscisic acid (ABA) has been employed by plants to facilitate the adaptive/tolerate response during stressful conditions. However, the interactive role of exogenously applied NO and ABA is very less studied at physiological, biochemical and molecular levels. The present study therefore, evaluated the effects of individual and simultaneous addition of exogenous NO donor SNP (100μM) and ABA (10μM) on photosynthesis, Calvin-Benson cycle enzymes, S-assimilation enzymes, oxidative stress components, and genotoxicity in Brassica juncea cv. Varuna, exposed to polyethylene glycol (PEG)-induced drought stress. Results showed that a loss induced by PEG was significantly surpassed by the application of NO or/and ABA with PEG for chlorophyll content, net photosynthestic rate (Pn), internal CO concentration (Ci), stomatal conductance (gs), transpiration rate (Tr), maximum photosystem II (PSII) efficiency (Fv/Fm), actual PSII efficiency (ΦPSII), intrinsic PSII efficiency (Fv´/ Fm´), photochemical quenching (qP), non-photochemical quenching (NPQ), electron transport chain (ETC), ribulose 1,5-bisphosphate carboxylase/oxygenase (RuBisCo), glyceraldehyde-3-phosphate dehydrogenase (GapDH), phosphoribulokinase (PRK), ATP-sulfurylase (ATP-S), and serine acetyltransferase (SAT) activities. The genomic template stability (GTS) (measured as changes in RAPD profiles) was significantly affected and showed varying degrees of DNA polymorphism, highest in PEG and lowest in PEG + NO and PEG + NO + ABA. Furthermore, the changes in RAPD profiles showed consistent results when compared with various photosynthetic and oxidative parameters. Altogether, this study concluded that supplementation of individual NO and together with ABA was more effective than individual ABA in alleviating PEG-induced drought stress in B. juncea L. seedlings.