Exogenous nitric oxide pretreatment protects Brassica napus L. seedlings from paraquat toxicity through the modulation of antioxidant defense and glyoxalase systems

To investigate the physiological and biochemical mechanisms of nitric oxide (NO)-induced paraquat (PQ) tolerance in plants, we pretreated a set of 10-day-old Brassica napus seedlings with 500 μM sodium nitroprusside (SNP - a NO donor) for 24 h. Then, three doses of PQ (62.5, 125 and 250 μM) were applied separately, as well as to SNP-pretreated seedlings, and the seedlings were allowed to grow for an additional 48 h. The seedlings treated with PQ showed clear, dose-dependent signs of oxidative stress, with elevated levels of lipid peroxidation (MDA, malondialdehyde), H 2 O 2 and O 2 - generation, and lipoxygenase (LOX) activity. Paraquat treatment disrupted pools of water-soluble antioxidants (ascorbate-AsA and reduced glutathione-GSH). Paraquat had different effects on the activities…