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

Elevated CO (eCO) 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 eCO conditions and promote biomass accumulation. To explore the mechanisms behind eCO-induced senescence and the potential mitigation through P supply, pot experiments were conducted under low and high P conditions during spring and autumn. The eCO-induced senescence was remarkable irrespective of P supply in spring, frequently over the optimum temperature (20°C), resulting in a rather lower biomass under eCO than under ambient CO (aCO). In contrast, in autumn, eCO enhanced biomass at optimal temperatures, particularly under high P conditions. Although leaf C/N ratios were similar under both CO levels in late spring, glucose concentrations were significantly higher under eCO, 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 eCO-induced senescence cannot be mitigated by increasing P supply, especially under non-optimal temperature conditions.