水稻根系联合固氮的研究 Ⅱ.水稻根系固氮酶活性的测定及固氮微生物的分离

本文报道在福建部分地区及盆栽中采集的800多个根样包括97个水稻品种的固氮酶活性检测结果及根系固氮微生物的分离。通过测定发现水稻根系具有固氮酶活性是较为普遍的,采用切根加培养基预培养后,其根内固氮酶活性出现率可达70～90％以上。水稻根系具有固氮酶活性的样品的分布,与水稻品种、植株生育期、种植地区以及土壤环境有关,固氮酶活性较高的根样大多出现在省肥耐瘦株型紧凑的品种,纬度较低、气候温暖的闽南地区,处于孕穗—灌浆的生育期以及盐碱土、坑田的土壤环境。几年来从有固氮酶活性的根系中分离到菌株1,317个,其中表现固氮酶活性的473株,占分离总数的36％。并发现这些分离的固氮茵的生长和固氮需要含有少量有机氮(如酵母膏)的培养基,对氧分压的要求因菌株不同而异。还检到一些真菌具有乙炔还原活性。

STUDIES ON THE ASSOCIATIVE SYMBIOSIS OF NITROGEN FIXATION IN RICE ROOTS Ⅱ. Assay of Nitrogenase Activity and Isolation of Nitrogen fixing Organisms from the Rice Roots

Determination of the nitrogenase activities was conducted on over 800 rice root samples from 97 varieties of rice collected at certain parts of paddy fields in Fujian province as well as special designed pot cultures. The nitrogen-fixing microorganisms were isolated from the root-systems of rice. With the acetylene reduction detection process, most of the samples of rice root-systems were found to possess nitrogenase activity. The sterilized preincubated excised root was found to have active nitrogen fixing ability, and the frequency of nitrogenase activity inside the rice root tissue determined attaining as high as over 70-90 percent. The rate of nitrogenase activity thus obtained from the samples showed closely correlated to rice varieties, duration of growth period growing regions as well as soil environments. Samples with higher root nitrogenase activity appeared mostly in those types of compact rice plants that grown in barren soils of the lower latitude with warmer climate in Southern Fujian at the booting up to milking stages as well as rice grown in saline-alkali soils and waterlogged fields. 1317 strains of microbes have been isolated successfully from the rice roots and among them 473 strains exhibited nitrogenase activity, making approximately 36 percent of the total amount isolated. The isolated nitrogen-fixing organisms grew well and fixed ambient air nitrogen normally They were adapted to such organic nitrogen as yeast extract in the media. The partial oxygen pressure requirement of the microbes varied from different strains. Acetylene reduction activities have Deen found also in some fungi eucaryotes.