亚低温下不同外源氮对山定子根系氮代谢活性的影响

试验以山定子(Malus baccata Borkh.)实生苗为试验材料,研究根域亚低温下不同外源氮(NO3-和NH4+)对山定子根系活力、根系氮代谢关键酶活性以及根系抗氧化酶活性的影响。结果表明,亚低温条件下,添加外源氮可在一定时间内提高山定子的根系活力;提高了山定子根系硝酸还原酶(NR)和谷氨酸合酶(GOGAT)活性,但降低了谷氨酰胺合成酶(GS)活性,谷氨酸脱氢酶(GDH)活性整体呈上升趋势。不同氮源对山定子根系氮代谢酶活性影响不同,NH4+处理的山定子根系GS活性和GDH活性高于NO3-处理。亚低温条件下,添加外源氮提高了根系过氧化物酶(POD)和过氧化氢酶(CAT)活性,但降低了超氧化物歧化酶(SOD)活性。因此,施加外源氮可缓解根域亚低温对植株生长的伤害。同时研究表明,两种外源氮对山定子根系响应亚低温具有不同的影响,为苹果生产中合理施用氮肥提供了理论基础。

Effects of Different Exogenous Nitrogen on Nitrogen Metabolism of Malus baccata Borkh. Roots Under Mild Hypothermia

The seedlings of Malus baccata Borkh. were used as materials to study the efficiency of exogenous nitrogen on root vigor, nitrogen metabolism, and activities of antioxidant enzymes in roots under mild hypothermia. The results showed that, under mild hypothermia exogenous nitrogen increased root vigor within a certain time, increased the activities of the nitrate reductase and glutamate synthase, but reduced glutamine synthetase activity, while glutamate dehydrogenase activity showed an upward trend as a whole. In addition, different kinds of nitrogen showed different effects on enzyme activities of root ni-trogen metabolism. The activities of glutamine synthetase and glutamate dehydrogenase by NH4+ treatment were higher than that by NO3- treatment. Under mild hypothermia, exogenous nitrogen significantly enhanced the activities of POD and CAT, but had negative effects on SOD activity. Therefore, exogenous nitrogen can alleviate the damage caused by mild hypothermia stress on the root zone. The results showed that two kinds of exogenous nitrogen had different effects on the response of mild hypothermia, which provided the theoretical basis for rational application of nitrogen fertilizer in apple production.