ANALYSIS OF THE MECHANISMS OF NITROGEN INHIBITION ON RHIZOBIA INFECTION ON PEANUT USING AGROBACTERIUM RHIZOGENES-MEDIATED TRANSGENIC HAIRY ROOTS

根际农杆菌介导的毛状根转化在花生（arachhis hypogaea） cv.Java 13的干燥成熟种子上进行了诱导。与对照植株相比，转化根与非转化芽组成的复合植株根系质量丰富，横向分枝多，分形维数高。复合植株接种缓生根瘤菌可诱导根瘤转化。转化后的根瘤表现出细菌区血红蛋白的产生和C_2H_2还原酶的活性，并表现出根瘤皮质区增大和根瘤皮质新生根的形态改变。研究了300 ppm N水平下硝态氮对接种缓生根瘤菌并在溶液培养基中培养的花生生长、根瘤形成和氮酶活性的影响。植株干重和总氮含量随培养基补氮时间的延长而变化，即生育前期补氮增加了根瘤数、根瘤鲜重和乙炔还原活性。在该水培系统中发现了钉钉和荚果形成。利用复合植株和该培养方法进一步研究硝酸盐对花生根瘤菌侵染的抑制机制。

Agrobacterium rhizogenes-mediated transformed hairy roots were induced on dry mature seed of peanut (Arachis hypogaea) cv.Java 13. Composite plants consisting of transformed roots with non-transformed shoots showed a root system with abundant root mass, more lateral branching and high fractal dimension compared to the control plant. The inoculation of Bradyrhizobium sp.to the composite plants led to the induction of transformed root nodules. Those transformed root nodules showed production of leghemoglobin in the bacterial zone and nitrogenase activity by C_2H_2 reduction assay, and exhibited morphological alterations such as enlargement of nodule cortex region and de novo root formation from nodule cortex.The effect of nitrate nitrogen at levels of 300 ppm N was investigated on the growth, root nodule formation and nitrogenase activity in peanut (cv.Chiba-handachi) inoculated with Bradyrhizobium and cultured in solution medium. Dry weight and total nitrogen content of the plant differed in response to the duration of supplement of nitrogen to the culture solution, i.e.supplement at early growing stage increased nodule numbers, nodule fresh weight and acetylene reduction activity. Pegging and pod formation were found on this hydroponic culture system.Further investigation of nitrate inhibition mechanisms on rhizobia infection on peanut is now in progress using the composite plant and this culture method.