[目的]研究不同氮素营养形态(不同比例NH4+/NO3-)对香蕉生长及根系质子泵活性的影响.[方法]在温室中水培巴西种香蕉(Musa AAA Cavendish cv.Baxi),设置5个处理:100%硝态氮处理(100%N);75%硝态氮和25%铵态氮处理(75%N+25%A);50%硝态氮和50%铵态氮处理(50%N+50%A);25%硝态氮和75%铵态氮处理(25%N+75%A);100%铵态氮处理(100%A).测定香蕉的生物量和N、P、K、Ca、Mg养分含量,并分离根系细胞膜,测定质子泵活性,建立植物生长状况与质子泵活性之间的联系.[结果]铵硝混合营养比单一的铵态氮或硝态氮营养对香蕉生长具有更好的生长效果,其中以50%硝态氮+50%铵态氮处理中香蕉植株的生物量最大,植物体内养分含量也最高;香蕉根际pH值与不同比例NH4+/NO3-有关,在100%铵态氮处理时最低,随着硝态氮比例的增加,pH值逐渐上升;香蕉根系细胞膜质子泵活性在100%铵态氮处理时最高,随着硝态氮比例的增加,质子泵活性逐渐降低.[结论]质子泵活性既与营养液中的不同比例NH4+/NO3-有关,也受到铵态氮或硝态氮吸收后根际pH值变化的影响.质子泵活性过高与过低都是植物生长受到外界胁迫后的一种应答,或是总体生长状况不良的一种反应.相反,质子泵活性处于一个相对稳定的适中状态才说明植物处于一个最佳的生长状态.[Objectives]To investigate the effect of nitrate/ammonium ratio on the growth of banana and roots plasma membrane H+-ATPase. [Methods]Brazilian varieties bananas(Musa AAA Cavendish cv.Baxi)were cultivated in hydroponics systems with different ratio of nitrate/ammonium. Five treatments, including 100% nitrate(100%N), 75% nitrate+25% ammonium(75%N+25%A), 50% nitrate+50% ammonium(50%N+50%A), 25% nitrate+75% ammonium(25%N+75%A)and 100% ammonium(100%A)were conducted. The plant biomass and nutrients, such as N, P, K, Ca, Mg contents were analyzed. Moreover, the plasma membrane H+-ATPase activity of banana roots was tested and its correlation with the banana plant growth was established. [Results]In comparison with the treatments of sole nitrogen resource, the treatment of 50% nitrate+50% ammonium(50% N+50% A)caused the greatest biomass of banana plants and the highest content of N, P, K in plants. The rhizospheric pH was related to the ratio of nitrate and ammonium. The pH was lowest under the 100% ammonium treatment, while the pH increased with the addition of nitrate in the root medium. The activity of plasma membrane H+-ATPase is highest under the 100% ammonium treatment, and decreased with the increased ratio of nitrate to ammonium. [Conclusions]The plasma membrane H+-ATPase activity is strongly influenced by the ammonium/nitrate ratio in the root medium and the rhizospere pH caused by the uptake of ammonium/nitrate by plant roots. Only under the suitable ratio of nitrate/ammonium in the nutrition solution, the activity of plasma membrane H+-ATPase is relatively balanced for the plant growth. In contrast, the high or low activity of plasma membrane H+-ATPase indicated an unfavorable situation for plant growth
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