Changes of Nitrogenase Activity in Sugarcane(Saccharum officinarum L.) and Its Response to Innoculate Nitrogen Fixation Bacteria

The nitrogenase activities at different growth periods of sugarcane by inoculating nitrogen fixing bacteria R16SH were investigated in two Brazilian nitrogen fixing sugarcane varieties('B1','B8'),and two local varieties('ROC22','ROC16').It had shown that the nitrogenase activities in roots and stalks were higher than those in leaves and sheathes in four cultivars,and it reached the summit in the rapidly elongating period or at the beginning of the elongating period in all organs.The Brazilian nitrogen fixing varieties 'B1'and'B8'after inoculation showed a better nitrogen fixing ability in roots compared to the control,which enhanced 13.22% and 12.42% respectively.The nitrogenase activities in the stems of 'B1' and 'ROC16' improved 12.19% and 12.02% respectively,the nitrogenase activities in leaves increased 8%～9%,the change in sheathes was the lowest among these organs.The nitrogen fixing ability was 'B8''B1''ROC22''ROC16'.'B8' showed significant different compared to 'ROC22' and 'ROC16'.It has inducing efficiency in height of 'B1'and'B8'and stem diameter of 'B1' by inoculating nitrogen fixing bacteria R16SH.The obvious effect was observed at the elongation stage.Therefore,it was shown that the nitrogenase activities were significantly different in organs,varieties and growth stage,and it was promoted in a certain extent by inoculating nitrogen fixing bacteria.The nitrogenase activities in roots and stalks showed significant difference compared to the control in these varieties(at P0.05 or P0.01),and the same results in the leaves in certain growth stage of 'B1' and 'B8' were also observed.The results indicated that the Brazilian cultivars had higher nitrogen fixation ability than Guangxi local cultivars.Brazilian cultivars were more sensitive to nitrogen fixing bacteria than Guangxi local cultivars.