Abstract:

Effects of exogenous sodium nitroprusside (SNP), a nitric oxide (NO) donor, on the salt tolerance of wheat (Triticum aestivum L.) seedlings indicated that NO donor significantly alleviated the growth inhibition, water loss and the decay of chlorophyll in wheat seedlings caused by 150 mmol/L NaCl salt stress, thus led to the promotion of salt tolerance against salt stress. Combined with 1 mg/mL hemoglobin treatment reverted the above SNP actions by restoring the growth of wheat seedlings and chlorophyll content to the level found in untreated wheat seedlings under salt stress. The specific role of NO in regulating the salt tolerance of wheat seedlings under salt stress was confirmed by using NaNO₂ and K₃[Fe(CN)₆] as control. Further investigation showed that the effect of both which might be related to the induction of plasma membrane H⁺-ATPase and H⁺-PPase (H⁺-pyrophosphatase) activities by NO in the roots of wheat seedling under salt stress. NO obviously enhanced the hydrolylic activities of H⁺-ATPase and H⁺-PPase, but did not affect the H⁺ transport ability across plasma membrane in wheat seedling roots under salt stress. Treatment with exogenous CaSO₄ and EGTA also showed that Ca²⁺ was vital to the NO induced activities of H⁺-ATPase and H⁺-PPase respectively in the roots of wheat seedling under salt stress. Investigation of NO on the content of Na⁺ and K⁺ in the roots of wheat seedlings illustrated that NO did not obviously affect the content of Na⁺, but significantly elevated the content of K⁺ as well as leading to the increase the ratio of K⁺ to Na⁺ in the roots of wheat seedling under salinity conditions. This was also important to believe that NO induced the adaptive abilities of wheat seedlings against NaCl salt stress.

Key words: Triticum aestivum, nitric oxide, salt tolerance, plasma membrane H⁺-ATPase, H⁺-PPase, K⁺/Na⁺