Premium
Effects of exogenous application and stem infusion of ascorbate on soybean ( Glycine max ) root nodules
Author(s) -
BASHOR CALEB J.,
DALTON DAVID A.
Publication year - 1999
Publication title -
new phytologist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.742
H-Index - 244
eISSN - 1469-8137
pISSN - 0028-646X
DOI - 10.1046/j.1469-8137.1999.00370.x
Subject(s) - leghemoglobin , antioxidant , root nodule , nitrogenase , chemistry , glycine , biochemistry , legume , nitrogen fixation , lipid peroxidation , oxidative phosphorylation , glutathione , nodule (geology) , botany , food science , biology , enzyme , nitrogen , paleontology , organic chemistry , amino acid
Numerous biochemical and physiological studies have demonstrated the importance of ascorbate (ASC) as a reducing agent and antioxidant in higher plant metabolism. Of special note is the capacity of ASC to eliminate damaging activated oxygen species (AOS) including O 2 −· and H 2 O 2 . N 2 ‐fixing legume nodules are especially vulnerable to oxidative damage because they contain large amounts of leghaemoglobin which produces AOS through spontaneous autoxidation; thus, ASC and other components of the ascorbate–reduced glutathione (ASC–GSH) pathway are critical antioxidants in nodules. In order to establish a meaningful correlation between concentrations of ASC and capacity for N 2 fixation in legume root nodules, soybean ( Glycine max ) plants were treated with excess ASC via exogenous irrigation or continuous intravascular infusion through needles inserted directly into plant stems. Treatment with ASC led to striking increases in nitrogenase activity (acetylene reduction), nodule leghaemoglobin content, and activity of ASC peroxidase, a key antioxidant enzyme. The concentration of lipid peroxides, which are indicators of oxidative damage and onset of senescence, was decreased in ASC‐treated nodules. These results support the conclusion that ASC is critical for N 2 fixation and that elevated ASC allows nodules to maintain a greater capacity to fix N 2 over longer periods.