低氧胁迫下外源硝态氮对樱桃根系功能及氮代谢相关酶活性的影响

Effects of exogenous NO_3^- on cherry root function and enzyme activities related to nitrogen metabolism under hypoxia stress

以樱桃组培苗'吉塞拉5号'(Prunun cerasus×P.canescens)为试材,采用营养液水培控制溶氧浓度的方法,研究了短期低氧胁迫下外源硝态氮对其根系功能及氮代谢相关酶活性的影响.结果表明:与对照(7.5mmol NO3-·L-1)相比,低氧加氮处理(15和22.5mmolNO3-·L-1)使樱桃体内代谢原料充足,保证了各类酶蛋白的合成,使植株根系活力升高,根系呼吸未受到明显抑制,与氮代谢相关的硝酸还原酶(NR)、谷氨酰胺合成酶(GS)及谷氨酸脱氢酶(NADH-GDH)活性升高,从而为低氧逆境下樱桃根系的吸收作用提供了足够的能量,保证了糖酵解和电子传递的顺利进行,并及时同化了NO3-还原生成NH4+,避免了铵毒害,缓解了樱桃的低氧伤害,且22.5mmol NO3-·L-1处理的缓解效果优于15mmol·L-1处理;低氧缺氮处理(0mmol NO3-·L-1)的樱桃植株根系活力下降,根系呼吸受到抑制,NR、GS及NADH-GDH活性降低.这说明低氧胁迫下,适当提高生长介质中的NO3-浓度可调控樱桃的根系功能及氮代谢,缓解低氧胁迫对樱桃根系的伤害.

A water culture experiment with controlled dissolved oxygen concentration was conducted to explore the effects of exogenous NO3- on the root function and enzyme activities related to nitrogen metabolism of cherry （ Prunun cerasus × P. canescens） seedlings under hypoxia stress. Comparing with the control （ 7. 5 mmol NO3- ·L -1） ,treatments 15 and 22. 5 mmol NO3- ·L -1 made the materials for plant metabolism abundant,ensured the synthesis of enzyme proteins,increased root activity,maintained root respiration,improved the activities of enzymes related to nitrogen metabolism,such as nitrate reductase （ NR） ,glutamine synthethase （ GS） ,and glutamate dehydrogenase （ NADH-GDH） in roots,and thereby,supplied enough energy for root respiration and NAD ＋ to glycolytic pathway,ensured electron transfer,and avoid ammonium toxicity under hypoxia stress. As a result,the injury of hypoxia stress to cherry plant was alleviated. Applying NO3 - at the concentration of 22. 5 mmol·L-1 was more advisable. However,NO3- deficiency （ 0 mmol·L -1） showed opposite results. The above results suggested that applying exogenous NO3- to growth medium could regulate cherry root function and nitrogen metabolism,and antagonize the damage of hypoxia stress on cherry roots.