In:
Soil Science Society of America Journal, Wiley, Vol. 50, No. 2 ( 1986-03), p. 349-354
Abstract:
Denitrification by Bradyrhizobium japonicum (formerly Rhizobium japonicum ) was characterized in two strains, USDA‐110 and USDA‐23, to determine the extent of denitrifying enzyme expression during symbiotic growth with soybean [ Glycine max (L.) Merr.]. The rhizobia grew in anaerobic batch cultures, depleting NO 3 ‐ and producing N 2 O in the presence of C 2 H 2 . Specific denitrifying activities of resting cells of rhizobia were compared with those of the common soil denitrifier Pseudomonas fluorescens , and were found to range from 14 to 18% of the P. fluorescens activity. Bacteroid specific activities were less than activities of free‐living rhizobial cells, though the ratio depended on the growth stage of the cells. Denitrification was observed in detached whole nodules containing either of the strains, but not in nodules formed by a NO 3 ‐ reductase mutant of B. japonicum 110. Denitrification rates of nodules were unaffected by the presence of external O 2 , though the rates were limited by the external NO 3 ‐ concentration. Denitrification by intact, nodulated soybean plants under aerobic conditions was observed. In the presence of NO 3 ‐ denitrification and N 2 fixation (C 2 H 2 reduction) occurred simultaneously. The estimated ratio of N denitrified to N fixed ranged from 0 to 0.3, depending on assay conditions. The observations suggest that denitrification in soybean nodules in the field can be a continuous process, independent of soil aeration. However, it is likely to be slow relative to N 2 fixation under most conditions.
Type of Medium:
Online Resource
ISSN:
0361-5995
,
1435-0661
DOI:
10.2136/sssaj1986.03615995005000020019x
Language:
English
Publisher:
Wiley
Publication Date:
1986
detail.hit.zdb_id:
241415-6
detail.hit.zdb_id:
2239747-4
detail.hit.zdb_id:
196788-5
detail.hit.zdb_id:
1481691-X
SSG:
13
SSG:
21
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