Leaf senescence in response to elevated atmospheric CO2 concentration and low nitrogen supply

This review reports the physiological and metabolic changes in plants during development under elevated atmospheric carbon dioxide concentration and/or limited-nitrogen supply in order to establish their effects on leaf senescence induction. Elevated CO2 concentration and nitrogen supply modify gene expression, protein content and composition, various aspects of photosynthesis, sugar metabolism, nitrogen metabolism, and redox state in plants. Elevated CO2 usually causes sugar accumulation and decreased nitrogen content in plant leaves, leading to imbalanced C/N ratio in mature leaves, which is one of the main factors behind premature senescence in leaves. Elevated CO2 and low nitrogen decrease activities of some antioxidant enzymes and thus increase H2O2 production. These changes lead to oxidative stress that results in the degradation of photosynthetic pigments and eventually induce senescence. However, this accelerated leaf senescence under conditions of elevated CO2 and limited nitrogen can mobilize nutrients to growing organs and thus ensure their functionality.