Graphene Oxide Enhances Drought Tolerance in Apple by Promoting <scp>ROS</scp> Scavenging and Regulating Amino Acid Contents

Graphene oxide (GO), a two-dimensional nanomaterial, has shown potential for improving plant stress tolerance. However, its involvement in, and mechanism of, regulating the drought stress response in apple plants remains unclear. In this study, we investigated the effects of GO on drought tolerance of M9-T337 plants under both short-term and long-term drought conditions. Results revealed that under short-term drought conditions, 0.1 and 1 mg L^-1 GO significantly alleviated drought-induced damage by reducing electrolytic leakage and MDA contents, while enhancing antioxidant enzyme activities and ROS scavenging. Under long-term drought conditions, 0.1 and 1 mg L^-1 GO improved photosynthetic rate and promoted root system development, thereby enhancing plant drought tolerance. Additionally, in M9-T337 plants, GO elevated the levels of γ-aminobutyric acid, proline, phenylalanine, arginine, and histidine, and upregulated the expression of MdCAT2, MdPOD2, MdDREB2A, MdERF1, and MdABI1. Taken together, this study connects GO with drought tolerance in apple plants, providing evidence that GO effectively enhances the drought tolerance of M9-T337 plants. These findings offer a promising strategy for the sustainable cultivation of apple in water-scarce regions through the application of nanomaterials.