Exogenous Pyrroloquinoline Quinone Application Enhances Low-Phosphorus Adaptation in Rice by Modulating Redox Homeostasis Under Variable Light.

Phosphorus (P) bioavailability in soil is often limited, restricting plant growth. Pyrroloquinoline quinone (PQQ) is a natural quinone compound with potent redox-cycling capabilities. In this study, we investigated the physiological effects of exogenously applied PQQ on rice adaptation to P deficiency. A P-sensitive rice cultivar (Meixiangzhan) was treated with 0.1 μM PQQ under different light intensities (High Light, HL: 800 μmol m-2 s-1; Low Light, LL: 300 μmol m-2 s-1) and P supplies (Sufficient P, SP; Deficient P, DP). The effects of PQQ on rice growth, P uptake, photosynthesis, and the antioxidant system were systematically analyzed. The optimal effect of PQQ occurred under high light combined with DP by increasing root surface area, root volume, and the number of root tips, thereby promoting root growth. Concurrently, PQQ activated antioxidant enzymes (SOD, POD, CAT), reduced the contents of H2O2, ROS, and MDA, while also enhancing acid phosphatase activity and leaf ATP content. Membership function analysis indicated that the combined physiological status was optimal under high light and DP conditions with PQQ addition. Our findings suggest that exogenous PQQ has the potential to enhance rice adaptation to P deficiency, with its efficacy depending on light intensity. Further research is needed to elucidate the underlying molecular mechanisms and validate them under field conditions.