Dazzo F B, Brill W J
Department of Bacteriology and the Center for Studies of Nitrogen Fixation, University of Wisconsin, Madison, Wisconsin 53706.
Plant Physiol. 1978 Jul;62(1):18-21. doi: 10.1104/pp.62.1.18.
Either NO(3) (-) (16 millimolar) or NH(4) (+) (1 millimolar) completely inhibited infection and nodulation of white clover seedlings (Trifoliin repens) inoculated with Rhizobium trifolii. The binding of R. trifolii to root hairs and the immunologically detectable levels of the plant lectin, trifoliin, on the root hair surface had parallel declining slopes as the concentration of either NO(3) (-) or NH(4) (+) was increased in the rooting medium. This supports the role of trifoliin in binding R. trifolii to clover root hairs. Agglutination of R. trifolii by trifoliin from seeds was not inhibited by these levels of NO(3) (-) or NH(4) (+). The results suggest that these fixed N ions may play important roles in regulating an early recognition process in the Rhizobium-clover symbiosis, namely the accumulation of high numbers of infective R. trifolii cells on clover root hairs.
16毫摩尔的硝酸根离子（NO(3) (-)）或1毫摩尔的铵根离子（NH(4) (+)）均可完全抑制接种三叶草根瘤菌的白三叶草幼苗（白车轴草）的感染和结瘤。随着生根培养基中硝酸根离子（NO(3) (-)）或铵根离子（NH(4) (+)）浓度的增加，三叶草根瘤菌与根毛的结合以及根毛表面植物凝集素三叶草凝集素的免疫可检测水平呈现平行下降趋势。这支持了三叶草凝集素在将三叶草根瘤菌与三叶草根毛结合中的作用。种子中的三叶草凝集素对三叶草根瘤菌的凝集作用不受这些浓度的硝酸根离子（NO(3) (-)）或铵根离子（NH(4) (+)）的抑制。结果表明，这些固定态氮离子可能在调节根瘤菌 - 三叶草共生关系中的早期识别过程中发挥重要作用，即在三叶草根毛上积累大量感染性三叶草根瘤菌细胞。
