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

Abstract Aims Global 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. Methods An 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 ( R 2 -stage ), pod initiation/seed development ( R 4 -stage ), and pod filling/initiation of crop maturity ( R 7 - 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 ( V c, max ), rate of RuBP regeneration ( J max ), and photosynthetic electron transport rate ( ETR )]. Results The drought-induced reduction in A N during the R 2 -stage stage was primarily attributed to a significant decrease in stomatal conductance ( g s ). In contrast, at the R 7 -stage , the reduction in A N was driven by limitations in the g s , V c, max , and J max . Notably, at the R 7 -stage , genotypes C76-16 and Lariat showed higher g s , ETR , and V c, max , contributing to increased A N and enhanced pod and kernel yield compared to AG18 and GA-09B. Conclusion A N reduction was driven by the biophysical limitation at the R 2 -stage and a combination of biophysical and biochemical limitations at the R 7 -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.