Elevated CO2 Modulates Hormonal Signaling and Galactose Metabolism to Improve Photosynthetic Performance and Water Use Efficiency in Peanut (Arachis hypogaea L.).

Atmospheric CO2 elevation promotes peanut biomass accumulation, yet the underlying molecular mechanisms remain unclear. This study investigated the physiological and molecular responses of two peanut cultivars (JH2 and JH54) to elevated CO2 (EC, 700 μmol·mol-1) versus ambient CO2 (CK, 400 μmol·mol-1) in open-top chambers, by analyzing photosynthetic traits, aboveground biomass, and leaf transcriptomic/metabolomic profiles. The results showed that EC significantly increased net photosynthetic rate, intercellular CO2 concentration, water use efficiency and biomass, but reduced stomatal conductance and pigment contents, with upregulated photosynthesis-related genes. Integrated multiomics revealed reprogrammed salicylic acid/abscisic acid signaling (lowering stomatal conductance and improving water use efficiency) and galactose metabolism (facilitating EC acclimation). Collectively, peanuts adapt to EC via coordinated transcriptomic-metabolomic adjustments in photosynthesis, hormone signaling and carbon metabolic reprogramming (especially galactose metabolism), providing a multilevel mechanistic insight into peanut's responses to rising atmospheric CO2.