中文摘要：

以巴西固氮甘蔗品种B1和B8为材料，在温室桶栽砂培条件下，对甘蔗施以含不同钼水平的营养液，以了解钼对甘蔗体内固氮菌的固氮酶活性的效应。结果表明，在含氮条件下，较低浓度的钼处理能提高甘蔗根内固氮菌的固氮酶活性，高浓度钼处理则能提高B1茎、叶片和B8茎中固氮菌的固氮酶活性；在无氮条件下，钼处理提高了B1叶片和茎中固氮菌的固氮酶活性，而B1根及B8根、茎、叶中固氮菌的固氮酶活性有所降低。此外，甘蔗根、茎、叶中固氮菌的固氮酶活性之间关系较为密切，根中固氮菌的固氮酶活性与叶片和茎中的都呈负相关。上述结果说明：巴西甘蔗在本地也具有一定的固氮能力；在不缺氮条件下，钼处理较利于调节甘蔗体内固氮菌的固氮酶活性，促进其固氮；而在缺氮条件下，钼处理不利于调节甘蔗体内固氮菌的固氮酶活性，抑制其固氮作用。

英文摘要：

Using two Brazilian nitrogen fixing sugarcane varieties （B1 and B8） were employed as the test materials, a barrel gravel culture was conducted to study the effects of molybdenum on nitregenase activity of nitrogen-fixing bacteria of sugarcane under greenhouse condition. Four Mo concentrations were adapted： 0 mg/L, 0.01 mg/L, 0.02 mg/L, and 0.04 mg/L. The experimental results showed that, under nitrogenous conditions, low Mo promoted nitregenase activity of nitrogen-fixing bacteria in roots, while high Mo increased that in stems of both two sugarcane varieties, and leaves of the variety B1. Under non-nitrogenous conditions, however, all Mo treatments increased the activities of nitrogenase of nitrogen fixing bacteria in leaves and stems of B1, but decreased that in leaves, stems and roots of B8 as well as that in roots of B1 compared with the control. There was a negative correlation between the nitregenase activities of nitrogen fixing bacteria in root and that in leaf and stem. All the results indicated that Brazilian sugarcane also had a nitrogen-fixing capacity in Guangxi, Mo was propitious to regulate nitrogenase activity of nitrogen-fixing bacteria in sugarcane under nitrogenous conditions, and promoted nitrogen fixing; while under non nitrogenous conditions, it was unpropitious to regulate the nitrogen activity and inhibited nitrogen fixation of nitrogen-fixing bacteria.