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.