[目的]为探讨植物硝酸还原酶活性的昼夜节律性.[方法]以Hoagland营养液栽培的抽穗期小麦为材料,在保持光、温恒定条件下,24h内采用活体法动态测定植株硝酸还原酶活性变化.[结果]小麦NRA在24h内的变化波动较大,从前一天20:00时开始到第2天上午11:00,酶活性没有显著差异；而14:00酶活性达到最高,且在0.05水平显著高于除11:00以外的其他时间点所测定的酶活性；下午17:00酶活性最低,在0.05水平显著低于除凌晨2:00以外的其他时间点所测定的酶活性.[结论]小麦NRA存在一定程度的自主节律性变化.%[Objective] The research aimed to study the circadian rhythm of nitrate reductase activity (NRA) in plant. [ Method ] The wheat in heading stage was used as materials to measure the dynamic changes of nitrate reductase activity ( NRA) within 24 hours under the conditions of constant light and temperature. [ Result] The fluctuation of NRA in wheat was changed greatly from 20:00 pm to 11:00 am. The enzyme activity remained constant, but at 14:00 the enzyme activity was the highest, and was higher than all the other time points except the enzyme activity measured at 11:00. The enzyme activity was the lowest at 17 :00, which was lower than all the other time points except the enzyme activity measured at 2:00. [Conclusion] There were autonomous rhythm changes of NRA in wheat in a certain degree.
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