Optimising Peanut Growth: Exogenous Calcium Enhances Photosynthesis in Phosphorus-Limited Environments

The study aimed to enhance peanut growth in phosphorus (P)-limited environments through exogenous calcium (Ca), exploring underlying mechanisms. Foliar application of calcium ions (Ca²⁺) and calmodulin (CaM) inhibitor (trifluoperazine, TFP) effects were investigated under P deficiency in a climate chamber. Parameters assessed included growth, biomass, nutrient accumulation, leaf expansion, carbohydrate metabolism, chlorophyll concentration, gas exchange, photosynthetic P-use efficiency (PPUE), chlorophyll fluorescence, and P700 redox state. Phosphorus deficiency reduced growth, leaf expansion, chlorophyll concentration, dry matter production, and photosynthetic capacity. Photosynthesis was feedback-limited, evidenced by negative correlations between sucrose concentration and net photosynthetic rate (Pn), and between starch concentration and sucrose phosphate synthase activity under low-P stress (LP). Exogenous Ca²⁺ application under P deficiency (LP+Ca) stimulated growth, biomass, and carbohydrate export, improving PPUE and photoprotection through enhanced cyclic electron flow and non-photochemical quenching. Conversely, foliar TFP application (LP + TFP) exacerbated the adverse effects of P deficiency on growth and photosynthesis, highlighting Ca²⁺-CaM's role in mitigating feedback inhibition. Exogenous Ca²⁺ application alleviated P-deficiency feedback limitations on photosynthesis primarily by enhancing growth/sink demand and protecting photosystems from photoinhibition. Exogenous Ca shows promise for cleaner peanut production in P-limited fields.