硝酸銨對於大豆固氮酵素，麩醯胺合成酵素及硝酸還原酵素活性以及化學組成的影響

Abstract

在大豆開花時期施以100毫莫耳硝酸銨，根瘤固氮酵素活性受到抑制，抑制程度隨著處理日數的增加而增加，若以單位根瘤來計算；由第一天活性為對照組的67%，降至第三、五天為對照組的25%，14%根瘤血紅素含量也隨著處理日數的增加而減少，由第一天其含量為對照組的90％降至第三、五天為對照組的62%，30%；硝酸還原酵素活性卻隨著硝酸銨處理日數的增加而增加，此現象與固氮酵素活性因硝酸銨處理而降低成強烈對比；硝酸銨的處理對於葉片及根瘤的麩醯胺合成酵素活性沒有顯著的影響。而發現硝酸銨的處理，可增加可溶性糖的利用率；而由根瘤及葉片硝酸還原酵素活性來比較，發現後者活性約為前者的兩倍，此顯示硝酸的還原作用主要是在葉片中進行；對於固氮作用因硝酸銨處理而受抑制的原因可能是因硝酸銨的處理造成根瘤血紅素合成速率的降低或分解速率的增高，引起血紅素含量的降低，血紅素攜帶氧功能的減弱，而促使固氮酵素活性的降低。

The nodular nitrogenase activity is inhibited while the plants are supplied with ammonium nitrate. The ratio of nitrogenase activity of the ammonium nitrate treated plant to that of the control is declined from 67% to 14% on the fifth day after treatment. The leghemoglobin in nodule is also decreased by the ammonium nitrate. The reduction of nitrogenase activity is compatible with the decrement of Leghemoglobin content by the treatment. The ammonium assimilation enzyme, glutamine synthetase, remaines unchange, however the nitrate reductase is enchanced by the ammonium nitrate. The nitrate reductase is obviousely induced by the pressence of ammonium nitrate, because no activity of this enzyme can be detected in the control plants. The leaf is the main tissue of plant to reduce and assimilate ammonium nitrate. It has been found that nitrate reductase activity in leaf is two fold higher than that in nodule. The nitrogenase activity is antiparrelled with nitrate reductase, no synergistic effect of nitrogenase activity and nitrate reductase on nitrogen metabolism is found in this study.