Protective role of nitric oxide (NO) on seed germination and growth was studied in mung bean seeds
(Vigna radiata) subjected to lead (Pb) stress. Germination percentage was increased up to 50 μM sodium
nitroprusside (SNP) and then steady declined. Under lead stress, and absence of SNP, percentage of
germination, fresh biomass, succulent value and the activity of α-amylase and protease as well as HATPase
were significantly decreased. This was accompanied with a significant increase of hydrogen
peroxide and malondialdhyde accumulation, catalase and guiacol peroxidase activities. Furthermore, total
phenolic compounds as well as some individual phenolic acids were increased in a dose-dependent
manner of lead. The protein pattern showed appearance of stress protein with M. M. of 110, 97 and 21
KDa at various lead stresses. Moreover, supplementation of SNP, as source of NO, increased fresh
biomass, succulent values and enhanced the activities of H-ATPase, α- amylase, protease, catalase and
guiacol peroxidase in lead stressed germinating bean seeds, whereas reduced the lead-induced increase in
lead, hydrogen peroxide, malondialdhyde and phenolics accumulation. A new stress protein with M.M.
65 KDa was appeared in all lead stressed seedlings in presence of SNP. Taken together these results
suggest that SNP could increase antioxidant capability in mung bean seeds leading to an improvement in
the plasma membrane integrity and enhancement of the activities of hydrolytic enzymes and hence, an
ameliorating role against the inhibitory impact of this toxicant on the germination and growth of mung
bean seeds under lead stress