The application of ascorbate or its immediate precursor, galactono-1,4-lactone, does not affect the response of nitrogen-fixing pea nodules to water stress.
Nitrogen fixation in legumes is dramatically inhibited by abiotic stresses, and this reduction is often associated with oxidative damage. Although ascorbate (ASC) has been firmly associated with antioxidant defence, recent studies have suggested that the functions of ASC are related primarily to developmental processes. This study examines the hypothesis that ASC is involved in alleviating the oxidative damage to nodules caused by an increase in reactive oxygen species (ROS) under water stress. The hypothesis was tested by supplying 5mM ASC to pea plants (Pisum sativum L.) experiencing moderate water stress (ca. -1 MPa) and monitoring plant responses in relation to those experiencing the same water stress without ASC. A supply of exogenous ASC increased the nodule ASC+dehydroascorbate (DHA) pool compared to water-stressed nodules without ASC, and significantly modulated the response to water stress of the unspecific guaiacol peroxidase (EC 1.11.1.7) in leaves and nodules. However, ASC supply did not produce recovery from water stress in other nodule antioxidant enzymes, nodule carbon and nitrogen enzymes, or nitrogen fixation. The supply of the immediate ASC precursor, galactono-1,4-lactone (GL), increased the nodule ASC+DHA pool, but also failed to prevent the decline of nitrogen fixation and the reduction of carbon flux in nodules. These results suggest that ASC has a limited role in preventing the negative effects of water stress on nodule metabolism and nitrogen fixation.
Zabalza
Ana
A
Departamento de Ciencias del Medio Natural, Universidad Pública de Navarra, Campus de Arrosadía, E-31006 Pamplona, Spain.
Gálvez
Loli
L
Marino
Daniel
D
Royuela
Mercedes
M
Arrese-Igor
Cesar
C
González
Esther M
EM
D000975:Antioxidants / Q000378:metabolism; D001205:Ascorbic Acid / Q000494:pharmacology*; D018533:Biomass; D003683:Dehydroascorbic Acid / Q000494:pharmacology; D005740:Gases / Q000378:metabolism; D005964:Glucosyltransferases / Q000378:metabolism; D007521:Isocitrate Dehydrogenase / Q000378:metabolism; D007783:Lactones / Q000494:pharmacology*; D009586:Nitrogen Fixation / Q000187:drug effects*; D018532:Pisum sativum / Q000187:drug effects* / Q000201:enzymology; D053204:Root Nodules, Plant / Q000187:drug effects* / Q000201:enzymology; D013312:Stress, Physiological / Q000187:drug effects* / Q000502:physiology; D013400:Sugar Acids / Q000494:pharmacology*; D014867:Water / Q000378:metabolism*
D000975:Antioxidants; D005740:Gases; D007783:Lactones; D013400:Sugar Acids; C534014:galactono-1,4-lactone; D014867:Water; D007521:Isocitrate Dehydrogenase; D005964:Glucosyltransferases; C022699:sucrose synthase; D001205:Ascorbic Acid; D003683:Dehydroascorbic Acid