Nitrogen fixation and hydrogen metabolism by Rhizobium leguminosarum isolates in pea root nodules

Abstract

A survey of 108 isolates of Rhizobium leguminosarum was conducted to determine the variation in H2 uptake and relative efficiency of N2 fixation in Pisum sativum L. root nodules and the relation of relative efficiency to plant dry weight and N content. Only 14 of the isolates exhibited significant uptake hydrogenase activity and none of these had sufficient hydrogenase activity to recycle all of the H2 produced by nitrogenase. In 74 of the isolates tested relative efficiencies of N2 fixation were less than 0.60.Twenty-nine of the isolates were ineffective, since total plant N at harvest did not differ significantly from uninoculated controls. The remaining 79 effective isolates could be divided into low-and high-efficiency groups. Plants which were inoculated with isolates from the two groups and harvested after 4 weeks did not differ significantly in plant dry weight or N content. Among the isolates with high relative efficiency of N2 fixation, two groups could be recognized: one possessing significant uptake hydrogenase activity, the other lacking hydrogenase activity but in which H2 evolution was low. Although the two groups did not differ with respect to plant dry weight or N content, the identification of this latter group may be of some significance for optimizing the efficiency of N2 fixation.

The effect of different temperatures on the fatty acid composition of Rhizobium leguminosarum bv. viciae in the faba bean symbiosis

“…Roxane were surface-sterilized (Chalifour & Nelson, 1987) and inoculated at sowing with 1 ml per seed of 3-d-o!d cultures of R. leguminosarum bv. viciae grown in modified Yeast Mannitol Broth medium (Nelson & Child, 1981) at 27 °C. Three seeds were planted per jar and thinned to one plant after seedling emergence (6 or 9 d after planting for the high and low temperature regimes, respectiv'ely).…”

Host Plant Cultivar Effects on Hydrogen Evolution by Rhizobium leguminosarum

“…This strain has been variously described in the literature as exhibiting Hup+ (3,23,24,26) and Hup-(14) phenotypes on P. sativum. Each of the groups studying strain 128C53 used a different pea cultivar as a host …”

“…This strain has been variously described in the literature as exhibiting Hup+ (3,23,24,26) and Hup- (14) photon flux density (400-700 nm) of 650 ,uE* m-2 s. Seeds were sterilized, germinated, and selected for uniformity before planting in sterile 750-ml Leonard jars containing vermiculite (10). All plants were provided with sterile N-free nutrient solution (10) and a single strain of Rhizobium in the Leonard jar.…”

The Relationship between H2 Evolution and Acetylene Reduction in Pisum sativum-Rhizobium leguminosarum Symbioses Differing in Uptake Hydrogenase Activity

“…Differences in RE2 have been attributed to the ability of some Rhizobium strains to produce an uptake hydrogenase enzyme which can recycle some or all of the H2 produced by nitrogenase (6, 1 1). Using single pea genotypes, Nelson and Child (17) and Ruiz-Argueso et al (19) (17). In one series of experiments with strain 128C52, open plastic pots were used for plant culture rather than Leonard jars.…”

“…Other reports indicate that the host plant genotype can alter the expression of the Hup gene in R. leguminosarum strains (1, 3). In some studies with peas, relatively high RE values have been reported even in symbioses having no measurable Hup activity, (2,(8)(9)(10)17), and these high efficiencies are considered to reflect a more efficient allocation of electrons to the reduction of nitrogen by nitrogenase. The RE of pea-Rhizobium symbioses can also be altered by environment and plant age.…”