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 (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 (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 R₂-stage stage was primarily attributed to a significant decrease in stomatal conductance (g_s). In contrast, at the R₇-stage, the reduction in A_N was driven by limitations in the g_s, V_{c, max}, and J_max. Notably, at the R₇-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 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.