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在玉米(Zea mays)和高粱的大土壤圈(直径29厘米,深20厘米)中利用乙炔还原方法测定固氮酶的活性。其酶活与从土壤中将根系移出,然后在有1％O_2下予培养一夜,并测定固氮酶活性的方法相比较。在6次实验和28个土壤圈所得的结果,土壤圈中固氮酶活性比从固样的土壤圈中移出根和经予培养的平均要弱14倍。圈中固氮酶活性是很低的,平均固氮速率不超过2.8gN/公顷·日。这表明土壤圈中的低酶活,并不是不适当气体交换之故,土壤圈的方法对大豆(Glycine max)和雀稗(Paspalum notatum),固氮酶活性测定,可得到满意的结果。 在巴西,已有过报导,认为生长的玉米有较高的固氮率。所用方法是将根切除,在测定前予培养一夜。(8)有人提示,氮的固定是由于螺旋菌(Spirillum sp)与玉米根联合作用的结果。在美国,研究人员,已经用从巴西土壤中分离得到的二株螺旋菌接种玉米,因为接种就观察到具有真正固氮酶活性。但是固氮酶活性,只有在经予培养并切除了根系的情况下,才能观察到。而非在大盆钵的植株分析中观察到。 本报告是比较经过予培养的和切除根系的同氮酶活性同在巴西土壤圈中生长玉米的固氮酶活性。
Nitrogenase activity was measured using the acetylene reduction method in large soil circles (29 cm in diameter and 20 cm in depth) of Zea mays and sorghum. The enzyme activity and removal of roots from the soil, and then incubated with 1% O_2 overnight, and the method of determination of nitrogenase activity compared. As a result of 6 experiments and 28 soil circles, the nitrogenase activity in the soil circle was 14-fold weaker than that on the average from the fixed-like soil circle. Nitrogenase activity in the loop is very low with an average nitrogen fixation rate of no more than 2.8gN / ha / day. This indicates that the low enzyme activity in the soil circle is not due to improper gas exchange. The soil circle method gives satisfactory results for the determination of Glycine max and Paspalum notatum, nitrogenase activity. In Brazil, it has been reported that grown corn has a higher nitrogen fixation rate. The method used is to excise the root and culture overnight before assaying. (8) It was suggested that nitrogen fixation is due to the combined effect of Spirillum sp and corn root. In the United States, researchers have inoculated corn with two strains of spirochaetes isolated from soil in Brazil because of the true azidase activity observed upon inoculation. However, nitrogenase activity was observed only after culturing and excising the root system. Not observed in plant analysis of large pots. This report compares nitrogenase activity of cultured and excised roots with that of corn grown in the Brazilian soil.