Elevated CO2-induced senescence in potato is associated with impaired antioxidant defense

Elevated carbon dioxide (eCO 2 ) generally promotes photosynthesis and biomass accumulation in C 3 crops, but these benefits may decline over time due to accelerated leaf senescence. However, the physiological mechanisms underlying eCO 2 -associated senescence remain unclear, particularly with respect to nitrogen (N) status and antioxidant defense. To clarify how N status and antioxidant defense are associated with senescence under eCO 2 , potato plants were grown under ambient CO 2 (aCO 2 ) or eCO 2 with low and high N supply. Elevated CO 2 did not affect the onset of leaf senescence but accelerated the rate of senescence progression. Increased N supply delayed senescence onset but did not alter the progression rate. Although eCO 2 increased plant dry weight at 28 and 42 days after transplanting, this effect disappeared at the final harvest. Elevated CO 2 reduced the activities of several antioxidant enzymes, particularly those involved in the ascorbate-glutathione cycle, and altered redox-related metabolites, suggesting weakened antioxidant defense and a tendency toward oxidative imbalance. Increased N supply improved leaf chlorophyll and protein contents at 42 days but did not prevent the decline in antioxidant enzyme activities under eCO 2 . These findings suggest that the accelerated progression of senescence under eCO 2 is associated with weakened antioxidant defense, whereas N availability mainly modulates the timing of senescence onset without substantially altering its subsequent progression.