Abstract:

To understand the regulative effect of exogenous nitric oxide on physiological response of naked oat (Avena nuda) seedlings under alkali stress, through nutrient solution cultivating in greenhouse, the naked oat cultivar, Dingyou No.6', was selected as the plant material and sodium nitroprusside (SNP) was used as nitric oxide donor to investigate the effects of Ca²⁺ on growth, reactive oxygen metabolism and osmotica accumulation of naked oat seedlings induced by exogenous nitric oxide under NaHCO₃ stress. The results showed that 25 μmol·L^-1 SNP or 6.5 mmol·L^-1 CaCl₂ could alleviate the inhibition of 75 mmol·L^-1 NaHCO₃ stress to the seedlings growth significantly, and the activities of superoxide dismutase, catalase, peroxidase, ascorbate peroxidase and plasma membrane H⁺-ATPase in leaves were enhanced, the contents of O₂^·-, H₂O₂, malondialdehyde were decreased, and the contents of ascorbic acid, soluble sugar, soluble protein and proline as well as K⁺/Na⁺ ratio were also increased significantly, in respectively. The effect of SNP was decreased after treatment of blocker of plasma membrane Ca²⁺ channel La³⁺ or extracellular Ca²⁺ chelant EGTA. The above results indicated that Ca²⁺ might play an important role in reactive oxygen metabolism, osmotica accumulation and balance of Na⁺ and K⁺ induced by exogenous nitric oxide in naked oat under alkali stress. The effect of nitric oxide here de pends on the content of Ca²⁺ in cytoplasm.

Key words: nitric oxide, Avena nuda, alkali stress, reactive oxygen metabolism, osmotica