Accelerate Senescence Reversed CO2-Fertilization Effect under Elevated CO2 in Potato: A Weak Relationship with Nitrogen Acquisition

Abstract

Accelerated senescence under elevated CO₂ (eCO₂) has not received sufficient attention, and its impact on the effect of CO₂-fertilization is unclear. To investigate the relationship between plant senescence and CO₂ concentration, a pot experiment was conducted in four potato genotypes under low CO₂ (LC), medium CO₂ (MC) and high CO₂ (HC) conditions. Nitrogen (N) uptake and cumulative transpiration were analysed to clarify whether eCO₂-induced senescence could be explained by low N uptake due to reduced transpiration. Compared to LC, the lifespan of potato plants under MC and HC was reduced by 3%–6% and 12%–32%, respectively, depending on the genotype. Biomass accumulation at full senescence was reduced when lifespan was shortened by approximately 5% and 10% under MC and HC, respectively. Cumulative transpiration was less affected by eCO₂ during early developmental stages but decreased under eCO₂ as plants aged. Plant water use decreased with a shortened lifespan under eCO₂, but there was no reduction in N uptake, which was attributed to the high N uptake per unit of water used. The results of this study indicate that senescence in potato genotypes is non-linearly related to CO₂ concentration and cannot be explained by reduced N acquisition via reduced transpiration. The positive effect of CO₂ fertilization can be reversed by accelerated senescence under eCO₂.