Exogenous GABA-Ca Alleviates Growth Inhibition Induced by a Low-P Environment in Peanuts (Arachis hypogaea)

Phosphorus (P) deficiency is a major global factor constraining peanut production. Exogenous γ-aminobutyric acid (GABA) and Ca²⁺ are essential to improve stress resilience in peanuts growing under low-P conditions. This study therefore examined the detailed physiological effects of GABA-Ca on restoring peanut growth under low-P conditions. These included the root-shoot ratio, leaf nutrients, photochemical activity, reactive oxygen species (ROS), cyclic electron flow (CEF), ATP synthase activity, and the proton gradient (∆pH), all of which were measured under low-P (LP, 0.5 mM) and optimized-P (1 mM) conditions. Specifically, supplying GABA-Ca under LP conditions regulated the ∆pH by causing adjustments in CEF and ATP synthase activities, buffering the photosystems' activities, restoring the antioxidant enzyme system, and lowering ROS production. Interestingly, exogenous GABA-Ca restored peanut growth under low-P conditions, possibly by the putative signaling crosstalk between GABA and Ca²⁺. The plausible signal amplification between GABA and Ca²⁺ suggested that the combination of GABA and Ca, may offer an effective strategy for enhancing peanut adaptation to low-P conditions. Moving forward, the strategic supplementation of GABA-Ca, either during cultivation or through the formulation of novel fertilizers, opens up many possibilities for better and more resilient plant production in soils with low P.