Effet des souches arctiques deRhizobiumsur la structure des nodules du sainfoin (Onobrychis viciifolia) et de leacute;gumineuses arctiques (AstragalusetOxytropisspp.)

摘要

Rhizobiumstrain N31, isolated from the arctic legumeAstragalus alpinus, nodulates sainfoin (Onobrychis viciifolia) as efficiently as strain SM-2, isolated from sainfoin. Nodule shape and tissue arrangement of 70-day-old plants infected by these two strains were examined. Sainfoin nodules formed by either strain N31or SM-2 were cylindrical, with indeterminate growth, and similar to those found on arctic legumes. However, in the active symbiotic zone of sainfoin nodules, bacteroids of strain N31were pleiomorphic or spherical and found individually or in groups of three, surrounded by the membrane envelope, whereas the bacteroids of strain SM-2 were elongated and enclosed in clusters of 3 to 12 by each membrane envelope. Thus, arctic strain N31affects the internal structure of sainfoin nodules. Nodules of arctic legumesA.alpinus,Oxytropis maydelliana, andOxytropis arctobia, infected with either strain N31or SM-2, contained lipid droplets, while sainfoin nodules did not show such characteristics. This phenomenon seems specific to arctic legumes and it is not influenced by the origin of the nodulating strain.