水稻根系联合固氮菌的种类及数量

Species and Enumeration of Nitrogen-fixing Bacteria in Rich Root Systems

用Iwao watanabe设计的培养基A,分离了水稻根际、根表和根内的固氮菌,并对其中75株好氧固氮菌进行了鉴定,发现水稻根区好氧固氮菌的数量随水稻生育期不同而变化,在水稻分蘖期,根际土壤中固氮菌数量最多,为2×10~7个细胞/克鲜土,根表为7×10~6个细胞/克鲜根,根内仅6.5×10~5个细胞/克鲜根,在抽穗扬花期则以根表为最多(2×10~9个细胞/克鲜根),根际为6×10~8个细胞/克鲜土,根内为6×10~7个细胞/克鲜根,水稻根系的好氧固氮菌,鉴定结果表明它们分属于八个属,其中肠杆菌科占25％,产碱菌属占24％,水稻根际以产碱菌属最多,克雷伯氏菌属为次,根表以芽孢菌属为主,其次为假单胞菌属,根内最多是固氮菌属,其次是芽孢杆菌属.

The nitrogen-fixing bacteria in rhizosphere and root surface and inner root of rice were isolated using Culture Medium A designed by Iwao watanabe. 75 strains of nitrogen-fixing bacteria were identified. The number of aerobic N2-fixing bacteria in the three parts of rice root has changed with growth stages. In the tillering stage, it was 2×107 N2-fixing bacteria per gram fresh soil in the rice rhizosphere, 7×106 N2-fixing bacteria per gram fresh root on the root surface and 6×107 N2-fixing bacteria per gram fresh root in inner root. For the heading stage, it was 2×109 N2-fixing bacteria per gram fresh root on the rice root surface, then 6×108 N2-fixing bacteria per gram fresh soil in the rhizosphere and 6×107 N2-fixing bacteria per gram fresh root in inner root. The result of identification suggested that those N2-fixing bacteria belong to 3 genera. The members of Enterobacteriaccae were 25 percent and those of Alcaligen were 24 percent. In the rhizosphere, most of the strains were Alcaligen, then were Klebsiella. On the root surf ace, the number of Bacillus was predominant and then Pseudomonas. The amount of Azotobacter was maximum in the inner root and that of Bacillus was less numerous than Azotobacter.