Sugar Accumulation Drives Elevated CO2-Induced Senescence in Solanum tuberosum.

Elevated CO2 (eCO2) can enhance plant growth, but it may also accelerate senescence, which could offset the growth benefits. Phosphorus (P) supply can enhance the photosynthetic rate under eCO2 conditions and promote biomass accumulation. To explore the mechanisms behind eCO2-induced senescence and the potential mitigation through P supply, pot experiments were conducted under low and high P conditions during spring and autumn. The eCO2-induced senescence was remarkable irrespective of P supply in spring, frequently over the optimum temperature (20°C), resulting in a rather lower biomass under eCO2 than under ambient CO2 (aCO2). In contrast, in autumn, eCO2 enhanced biomass at optimal temperatures, particularly under high P conditions. Although leaf C/N ratios were similar under both CO2 levels in late spring, glucose concentrations were significantly higher under eCO2, indicating that sugar accumulation, rather than nitrogen deficiency, contributed to senescence. Additionally, chlorophyll degradation was delayed under high P conditions, though P fertilization did not prevent senescence. These results suggest that yield reductions caused by eCO2-induced senescence cannot be mitigated by increasing P supply, especially under non-optimal temperature conditions.