Nitric oxide induced Cd tolerance and phytoremediation potential ofB. junceaby the modulation of antioxidant defense system and ROS detoxification

The present study designed to illustrate correlation between cadmium induced stress and plant growth, photosynthetic pigments, morphological and physiological attributes. To study these parameters 2 weeks old seedling ofB. junceawere subjected to 50 mu M Cd, 100 mu M Cd and 100 mu M SNP separately and in combination with SNP. After 96 h, the treated plant were harvested to analyze the cellular homeostasis and metal tolerance mechanism via examining growth, stress parameters, enzymatic and non enzymatic antioxidants and expression level of NR. Higher level of Cd (100 mu M) significantly increased accumulation of reactive oxygen species and malonaldehyde content in comparison to 50 mu M Cd. Exogenous supplementation of SNP (100 mu M) to 50 mu M Cd treated plant had an additive effect on plant growth by improving the level of proline, photosynthetic pigments and activities of enzymatic antioxidants which was confirmed by histochemical staining for NADPH-d and NO fluorescence from DAF-DA staining in roots ofB. juncea. Applying SNP to 50 mu M Cd exposedB. juncearoots enhanced NR activity by 1.36 folds and increased NO production by 1.12 folds than individual Cd treated roots. In addition, semi quantitative RT-PCR study revealed the induction ofBjNRwas more pronounced in 50 mu M Cd treated roots in comparison to 100 mu M Cd treated roots. The present finding revealed NO confers increasedB. junceatolerance to Cd stress by stimulation of antioxidants and reestablishment of cellular redox status. Different biochemical analysis showed that plant growth, photosynthetic pigment and antioxidants were positively correlated with NO and it's negatively correlated with oxidative stress biomarkers. Therefore, NO is gaseous signalling molecule with potential role in Cd detoxification mechanism inB. juncea.

Automated summary

The present study illustrated the correlation between cadmium-induced stress and plant growth, photosynthetic pigments, and physiological attributes. The results showed that nitric oxide (NO) enhanced the tolerance of B. juncea to Cd stress by stimulating antioxidants and restoring cellular redox status. Plant growth, photosynthetic pigment levels, and antioxidants were positively correlated with NO, while they were negatively correlated with oxidative stress biomarkers. This suggests that NO plays a potential role in the detoxification mechanism of Cd in B. juncea.