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Continuous CO 2 enrichment leads to increased nodule biomass, carbon availability to nodules and activity of carbon‐metabolising enzymes but does not enhance specific nitrogen fixation in pea
Author(s) -
Cabrerizo Pablo M.,
González Esther M.,
AparicioTejo Pedro M.,
ArreseIgor Cesar
Publication year - 2001
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 - 10.1034/j.1399-3054.2001.1130105.x
Subject(s) - nitrogen fixation , phosphoenolpyruvate carboxylase , sucrose synthase , nitrogenase , nitrogen , carbon fixation , sucrose , metabolism , biochemistry , root nodule , carbon fibers , biology , nitrogen cycle , chemistry , enzyme , photosynthesis , organic chemistry , materials science , composite number , invertase , composite material
Recent research has shown that nodule nitrogen fixation is limited under a wide range of environmental constraints by lowered carbon flux within the nodule due to down‐regulation of sucrose synthase activity. The aim of this work was to elucidate whether an increase in both carbon flux and activity of enzymes of carbon metabolism in nodules may lead to an increased nitrogen fixation. We report the effects caused by a continuous exposure to atmospheric CO 2 enrichment in nodulated pea plants. CO 2 enrichment led to an enhanced whole‐plant growth and increased nodule biomass. Moreover, nodules of plants grown at increased CO 2 showed a higher sugar content as well as enhancement of some activities related to nodule carbon metabolism, such as sucrose synthase, UDP glucose pyrophosphorylase and phosphoenolpyruvate carboxylase. Indeed, acetylene reduction activity, measured by the classical technique, was increased more than four times. However, when specific nitrogen fixation was determined as hydrogen evolution, no significant differences were detected, consistent with the lack of changes of enzymes involved in nitrogen metabolism such as glutamate synthase and aspartate aminotransferase. These results are discussed in the context of the regulation of nitrogen fixation and nodule metabolism.