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Role of oxygen limitation and nitrate metabolism in the nitrate inhibition of nitrogen fixation by pea
Author(s) -
Kaiser Brent N.,
Layzell David B.,
Shelp Barry J.
Publication year - 1997
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/j.1399-3054.1997.tb01818.x
Subject(s) - nitrogenase , nitrate , nitrate reductase , nitrogen fixation , pisum , sativum , biology , nitrogen , oxygen , botany , chemistry , horticulture , ecology , organic chemistry
The impact of nitrate (5–15 m M , 2 to 7 days) on nitrogenase activity and nodule‐oxygen limitation was investigated in nodulated, 21‐day‐old plants of a near‐isogenic nitrate reductase‐deficient pea mutant (A3171) and its wild‐type parent ( Pisum sativum L. cv. Juneau). Within 2 days, 10 or 15 m M nitrate, but not 5 m M nitrate, inhibited the apparent nitrogenase activity (measured as in situ hydrogen evolution from nodules of intact plants) of wild‐type plants; none of these nitrate levels inhibited the apparent nitrogenase activity of A3171 plants. Nodule‐oxygen limitation, measured as the ratio of total nitrogenase activity to potential nitrogenase activity, was increased in both wild‐type and A3171 plants by all nitrate treatments. By 3 to 4 days the apparent nitrogenase activity of A3171 and wild‐type plants supplied with 5 m M nitrate declined to 53 to 69% of control plants not receiving nitrate. By 6 to 7 days the apparent nitrogenase activity of A3171 plants was similar to the control value whereas that of the wild‐type plants continued to decline. From 3 to 7 days, no significant differences in nodule‐oxygen limitation were observed between the nitrate (5 m M ) and control treatments. The results are interpreted as evidence for separate mechanisms in the initial (O 2 limitation) and longer‐term (nitrate metabolism) effects of nitrate on nitrogen fixation by effectively nodulated pea.