Growth, Nutrient Accumulation, and Root Architecture Responses of Cucumber Plants to Different Graphene Oxide Concentrations

Graphene oxide (GO) has shown great potential in agricultural applications, however, its concentration-dependent effects on cucumber (Cucumis sativus L.) growth, nutrient absorption, and root architecture remain unclear. In the present study, a hydroponic experiment was conducted with different GO concentrations (0.5, 1.0, and 2.0 mg L−1) and setting the non-GO treatment (0.0 mg L−1) as the control for cucumber plants (cv. Qingbaizao). The results showed that low to moderate concentrations (0.5–1.0 mg L−1) significantly promoted cucumber growth, increased shoot and root biomass, enhanced the accumulation of nitrogen, phosphorus, and potassium, and optimized root architecture by increasing cellulose and hemicellulose content. In contrast, high GO concentrations (2.0 mg L−1) exhibited significant inhibitory effects, reducing plant growth indicators, inhibiting nutrient accumulation, particularly in shoots, damaging root structure, and leading to obvious damage to root apical vascular bundles and disrupted the structural integrity of root tips. Further analysis revealed that the regulatory effect of GO on cucumber growth was closely related to its influence on root uptake capacity and root architecture optimization, as differentially expressed genes in ‘GO and Control’ comparison was remarkably enriched in phenylpanoid biosynthesis. This study systematically explores the concentration-dependent responses of cucumber growth, nutrient accumulation, and root architecture to GO, clarifies the suitable concentration range of GO for cucumber growth promotion, and provides theoretical basis and technical reference for the rational application of GO in cucumber cultivation.