Biophysical and biochemical limitations to photosynthesis and yield of peanut (Arachis hypogaea L.) under water-deficit stress

AimsGlobal peanut production is constrained by the frequency and severity of drought. New insights into photosynthetic biophysical and biochemical limitations under water-deficit stress are important to enhance peanut photosynthetic efficiency and production. This study examines the combined effects of water deficit, genotype, and growth stage on peanut physiology.MethodsAn experiment was conducted during three growing seasons (2020 - 2022) to evaluate peanut genotypes (AG18, C76-16, GA-09B, and Lariat) at three developmental stages: flowering/peg development (R2-stage), pod initiation/seed development (R4-stage), and pod filling/initiation of crop maturity (R7-stage). The study was carried out under well-watered and water-deficit conditions. We quantified the biophysical (stomatal conductance) and biochemical limitations [the maximum rate of carboxylation (Vc, max), rate of RuBP regeneration (Jmax), and photosynthetic electron transport rate (ETR)].ResultsThe drought-induced reduction in AN during the R2-stage stage was primarily attributed to a significant decrease in stomatal conductance (gs). In contrast, at the R7-stage, the reduction in AN was driven by limitations in the gs, Vc, max, and Jmax. Notably, at the R7-stage, genotypes C76-16 and Lariat showed higher gs, ETR, and Vc, max, contributing to increased AN and enhanced pod and kernel yield compared to AG18 and GA-09B.ConclusionAN reduction was driven by the biophysical limitation at the R2-stage and a combination of biophysical and biochemical limitations at the R7-stage. Furthermore, physiological strategies such as maintaining higher stomatal conductance while reducing photosystem II damage, as shown by C76-16, could be an effective drought tolerance strategy for maintaining high pod yield.