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Peanut nodules have been reported to have several times highernitrogenase activity (C2H2) than cowpea and siratro nodulesinduced by the same rhizobial strains. The unique morphologicalmodification of the peanut bacteroids has been considered tobe the cause for such enhanced activity. To investigate thispossibility, nitrogenase activities of isolated peanut and cowpeabacteroids were compared. Peanut bacteroids showed low initialrates of C2H2 reduction which increased with time, but for cowpeabacteroids higher initial rates decreased with time. Moreover,the gases used as diluent for O2 (N2, Ar, or He) were foundto influence O2 tolerance and C2H2-reduction rates of bacteroids. 相似文献
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Bacteroids, formed by the same strain of Rhizobium, were isolatedanaerobically from peanut and cowpea root nodules and theirC2H2 reduction activities were measured. Measurements were startedin a pure N2 atmosphere followed by stepwise addition of smallamounts of O2. The procedures may have general application andare described in detail. With increasing O2 level, a gradualincrease in nitrogenase activity was observed which reacheda peak, presumably at the optimum availability of O2 to bacteroids,and then declined. The maximum activity attained by isolatedbacteroids of cowpea was much higher than that obtained frommeasurement of activities of intact nodules and their bacteroidcontent, whereas for peanut the two were nearly equal. The resultsindicated that intranodular conditions are probably responsiblefor the difference in nitrogenase activities of peanut and cowpeanodules rather than the unique morphological modification ofpeanut bacteroids. Key words: Root nodules, Peanut, Cowpea, Bacteroids, Nitrogenase activity 相似文献
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Structure and Organization of Effective Peanut and Cowpea Root Nodules Induced by Rhizobial Strain 32H1 总被引:1,自引:0,他引:1
A comparison of the structure and organization of nodular tissuesand bacteroids of peanut and cowpea induced by Rhizobium sp.strain 32H1 was madc 4 to 5 weeks after inoculation when nitrogenaseactivity reaches the peak. Observations revealed major differencesthat may have a role in the different rates of nitrogen fixationshown by the two species. All cell types in cowpca nodules werelarger than those of peanut. The inner cortex of cowpea hadan endodermis-like layer of cells which was absentin peanut. All cells in the bactcroidai zone of peanut wereinfected but in cowpca many remained free of bactcroids. Thebacteroid containing cells of peanut were isodianietrical anduniform in size with a central vacuole and a nucleus surroundedby tightly arranged bactcroids enclosed singly in peribacteroidalmembrane sacs. Such cells in cowpea were mostly elongated witha nucleus and one or more vacuoles. The bacteroids within cowpeacells were arranged without any particular order with more spacefor host cellular material. They were mostly present singlyin peribacteroidal membrane sacs which sometimes fused to enclosemore than one bactcroid. The hosts seem to play the dominantrole in the differentiation of nodular tissue and the morphogenesisof bacteroids in symbiotic systems induced by the same strainof Rhizobium. Key words: Peanut, Cowpea, nodule structre 相似文献
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