title: Growth under elevated atmospheric CO(2) concentration accelerates leaf senescence in sunflower (Helianthus annuus L.) plants.
abstract: Some morphogenetic and metabolic processes were sensitive to a high atmospheric CO(2) concentration during sunflower primary leaf ontogeny. Young leaves of sunflower plants growing under elevated CO(2) concentration exhibited increased growth, as reflected by the high specific leaf mass referred to as dry weight in young leaves (16 days). The content of photosynthetic pigments decreased with leaf development, especially in plants grown under elevated CO(2) concentrations, suggesting that high CO(2) accelerates chlorophyll degradation, and also possibly leaf senescence. Elevated CO(2) concentration increased the oxidative stress in sunflower plants by increasing H(2)O(2) levels and decreasing activity of antioxidant enzymes such as catalase and ascorbate peroxidase. The loss of plant defenses probably increases the concentration of reactive oxygen species in the chloroplast, decreasing the photosynthetic pigment content as a result. Elevated CO(2) concentration was found to boost photosynthetic CO(2) fixation, especially in young leaves. High CO(2) also increased the starch and soluble sugar contents (glucose and fructose) and the C/N ratio during sunflower primary leaf development. At the beginning of senescence, we observed a strong increase in the hexoses to sucrose ratio that was especially marked at high CO(2) concentration. These results indicate that elevated CO(2) concentration could promote leaf senescence in sunflower plants by affecting the soluble sugar levels, the C/N ratio and the oxidative status during leaf ontogeny. It is likely that systemic signals produced in plants grown with elevated CO(2), lead to early senescence and a higher oxidation state of the cells of these plant leaves.
authors: Departamento de Botánica, Ecología y Fisiología Vegetal, Área de Fisiología Vegetal, Universidad de Córdoba, Campus de Rabanales, Edificio Celestino Mutis (C4), 3ª planta, E-14071 Córdoba, Spain. b42matsl@uco.es
authors: Lourdes
authors: L
authors: de la Mata
authors: Purificación
authors: P
authors: Cabello
authors: Purificación
authors: P
authors: de la Haba
authors: Eloísa
authors: E
authors: Agüera
mesh_terms: D060387:Ascorbate Peroxidases / Q000378:metabolism; D001272:Atmosphere / Q000737:chemistry*; D018533:Biomass; D050260:Carbohydrate Metabolism / Q000187:drug effects; D002244:Carbon / Q000378:metabolism; D057486:Carbon Cycle / Q000187:drug effects; D002245:Carbon Dioxide / Q000494:pharmacology*; D002374:Catalase / Q000378:metabolism; D006368:Helianthus / Q000187:drug effects / Q000254:growth & development*; D006861:Hydrogen Peroxide / Q000378:metabolism; D009584:Nitrogen / Q000378:metabolism; D010860:Pigments, Biological / Q000378:metabolism; D018515:Plant Leaves / Q000187:drug effects / Q000201:enzymology / Q000254:growth & development*; D054046:Plant Stomata / Q000187:drug effects / Q000502:physiology
chemical_list: D010860:Pigments, Biological; D002245:Carbon Dioxide; D002244:Carbon; D006861:Hydrogen Peroxide; D060387:Ascorbate Peroxidases; D002374:Catalase; D009584:Nitrogen