When the first fully expanded leaf of wheat (Triticum aestivum L.) seedlings with two leaves were treated with different concentrations (0.05, 0.1, 0.2 and 0.5 mmol/L) of nitric oxide donor, sodium nitroprusside (SNP), the contents of hydrogen peroxide (H2O2) and malondialdehyde (MDA) were reduced by the lower concentrations (0.05, 0.1 and 0.2 mmol/L), but enhanced by the higher concentration of SNP (0.5 mmol/L). The protective effect of 0.1 mmol/L SNP was the most obvious. Furthermore, the treatment with 0.1 mmol/L SNP on the above seedlings until the fourth leaves were fully expanded attenuated the accumulation of H2O2, superoxide anion radical (O2-. ) and MDA, also counteracted the degradation of chlorophyll and soluble proteins, especially rubisco, both leading to the effective delay of aging process in wheat leaves. The effects of different SNP concentrations (0.05, 0.1, 0.2, 0.5, 1.0 and 5.0 mmol/L) also displayed a dual role in an aging experiment of chloroplasts in vitro, one of which, 0.2 mmol/L SNP treatment, protected the membrane structure and attenuated the degradation of rubisco effectively. Based on the present results, it was inferred that lower concentrations of nitric oxide (NO) might play a role in delaying aging process in wheat leaves, i.e., might attribute to the decrease the level of reactive oxygen species (ROS) and the alleviation of further oxidative damage caused by ROS.
屠 洁 沈文飚 徐朗莱
（南京农业大学生命科学学院，南京 2 1 0 0 9 5 ）
摘要： 用不同浓度(0.05、0.10、0.20、0.50 mmol/L)的外源一氧化氮(nitric oxide，NO)供体硝普钠(sodiumnitroprusside，SNP)处理正常生长小麦(Triticum aestivum L.)叶片(二叶一心期时全展第一叶)。结果显示低浓度SNP(0.05、0.10、0.20 mmol/L)可以明显降低叶片H2O2 和MDA 的水平，其中0.10 mmol/L SNP 的作用最为明显；而较高浓度SNP(0.50 mmol/L)则作用相反。进一步采用0.10 mmol/L SNP 处理不同叶位的小麦叶片(四叶一心期)，结果表明低浓度NO 对不同老化阶段中叶片的H2O2、O2-.和MDA 累积都有缓解作用,并明显减缓叶绿素、可溶性叶蛋白尤其是Rubisco 的降解,有效延缓了叶片的老化进程。在完整叶绿体体外老化实验中也发现，不同浓度SNP(0.05、0.10、0.20、0.50、1.00、5.00 mmol/L)的作用同样表现双重性,其中0.20 mmol/L SNP 对膜结构及Rubisco保护作用最明显。上述结果证实,低浓度外源NO可延缓小麦叶片的老化过程，并可能与其降低叶片活性氧(ROS)水平及缓解氧化损伤有关。
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