一氧化氮对盐胁迫下小麦幼苗根生长和氧化损伤的影响

Effects of Nitric Oxide on Root Growth and Its Oxidative Damage in Wheat Seedling Under Salt Stress

0.05和0.10 mmol/L一氧化氮(NO)供体硝普钠(sodium nitroprusside,SNP)处理明显减轻NaCl浓度为150 mmol/L左右的盐胁迫对小麦幼苗根生长的抑制效应,其中0.05mmol/L的SNP效果最明显;0.30mmol/L以上的SNP处理对根抑制无明显缓解作用;当NaCl浓度大于300 mmol/L时,各种浓度的SNP均不能减轻盐胁迫对根生长的抑制。以NO清除剂血红蛋白(hemoglobin,Hb)以及NO_x^-,K_3Fe(CN)_6等为对照,观察到0.05 mmol/L的SNP能不同程度地提高150 mmol/L盐胁迫下小麦幼苗根尖细胞中超氧化物歧化酶(SOD)、过氧化物酶(POD)和抗坏血酸过氧化物酶(ascorbate peroxidase,APX)活性,明显降低MDA、H_2O_2和O_2^-的积累,阻断盐胁迫诱导的根尖细胞DNA片段化,表明NO能有效缓解盐胁迫引起的小麦幼苗根尖细胞的氧化损伤。

Effects of nitric oxide (NO), a sub stance newly found to have protective functions in plants, on root growth of wheat (Triticum aestivum L. Yangmai 158) seedlings under salt stress were studied. Sodium nitroprusside (SNP), an NO donor, markedly alleviated the inhibitory effect of salt on root elongation at salt concentrations around 150 mmol/L, but was ineffective when NaCl concentration was at 300 mmol/L or higher (Fig. 1). It was most effective at 0.05-0.1mmol/L, and had harmful effect at 0.30-5mmol/L. Furthermore, when wheat seedling roots were treated with 150 mmol/L NaCl in combination with 0.05 mmol/L SNP and NO scavenger (hemoglobin, Hb), NO_3^-/NO_2^- and K_3Fe(CN)_6 as controls, both of which were the two other major products besides NO when SNP dissolved in water, respectively, activities of superoxide dismutase (SOD), peroxidase (POD) and ascorbate peroxidase (APX) were enhanced to some extent. While, the generation of O_2^- and the accumulation of MDA and H_2O_2 were alleviated (Figs.2-4). DNA laddering was observed when wheat seedling roots exposed to 150 mmol/L NaCl for 6 d, also suggesting that salt stress might induce oxidative damage in root-tips. In combination with hemoglobin, NO_2^-/NO_3^- and K_3Fe(CN)_6 as controls, the results showed that NO could block DNA ladders (Fig.5). Above results suggest that it is NO rather than any substances which is protecting root-tip cells of wheat seedlings from oxidative damage caused by salt stress.