increasing the tolerance of canola plant using nitric oxide under lead and drought stress

Lead and drought stress have negative effects on plant growth and decrease crop production. in recent years, many studies have been reported on the role of nitric oxide (no) in reducing these effects. the present study was conducted on brassica napus l. to investigate the interaction of lead, drought, and their combination with no using hyola 401 cultivars. one hundred (100) μmol / l lead with pb (no3)2, drought with 0.5% polyethylene glycol (peg) 6000 (-0.003 mpa), and no with 100 μmol / l sodium nitroprusside (snp) were used. lead and its combined treatment significantly decreased growth while drought stress affected only shoots. no treatment reduced negative effects on plant growth. adding no in the lead treated plants under drought stress caused an increase in soluble sugar contents. plant proline significantly increased by application of no in control, lead treatment, and simultaneous lead and drought treatment. a significant increase in the activity of the enzymes assayed (peroxidase and catalase) was observed in the plant exposed to lead and its combination with drought stress. the use of no caused a significant decrease in the activity of these enzymes. the antioxidant role of no may be the reason for this decrease in activities.