Symbiosis between plants of family Fabaceae and bacteria genus Rhizobium is the most widespread interaction, in which atmospheric nitrogen is reduced into ammonia. This highly oxygen-sensitive process is performed by endosymbiotc forms of rhizobia called bacteroids, which occupy newly formed plant organs called root nodules. The goal in this paper was to explore the differences in the (ultra)structure and Reactive Oxygen Species (ROS) localization in two symbiotic interactions between legume model plant Medicago truncatula Gaertn. and bacteria from genus Sinorhizobium. Two bacterial strains—Sinorhizobium meliloti 1021 and Sinorhizobium medicae 419 have the ability of inducing root nodules on the Medicago truncatula, however, such nodules differ in effectiveness of biological nitrogen fixation. We demonstrated that root nodules made of S. medicae 419 [fully effective (F++)] induce a lower number of nodule per plant in comparison to S. meliloti 1021—(partially effective F±). Although the differences in the structure are scant, there are some discrepancies in the ultrastructure. In the meristem of F± nodules, there are Cajal bodies and a lower number of vacuole profiles by larger size in comparison to the F++. Nodules F++ have a thicker interzone and store less starch than F+/, while they have higher esterase activity. Localization of different ROS seems to be comparable in the two type of nodules but interestingly, there is not any Nitric Oxide (NO) in the infection thread of F± root nodules.

豆科植物与根瘤菌属之间的共生是最广泛的相互作用，其中大气中的氮还原为氨。这种高度对氧气敏感的过程是通过根瘤菌的内生菌形式（称为类细菌）来进行的，这种形式占据着新形成的植物器官（称为根瘤）。本文的目的是探讨豆科植物模型plant藜苜蓿Gaertn在两种共生相互作用中的（超）结构和活性氧（ROS）定位的差异。和根瘤菌属的细菌。两种细菌strains-根瘤菌1021和苜蓿medicae419具有在run藜苜蓿上诱导根瘤的能力，但是，这种根瘤在生物固氮的有效性方面有所不同。我们证明，与苜蓿链球菌相比，药用链球菌419 [完全有效（F ++）]制成的根瘤诱导每株植物的根瘤数更少1021-（部分有效F±）。尽管结构上的差异很少，但超微结构仍存在一些差异。在F±结节的分生组织中，与F ++相比，有Cajal体和较大数量的液泡轮廓。结节F ++具有较厚的中间区，并且与F ++ /相比，其淀粉存储量更少，而它们的酯酶活性更高。两种结节中不同ROS的定位似乎是可比的，但有趣的是，F±根结节的感染线中没有任何一氧化氮（NO）。