Effect of graphene oxide on carbon and nitrogen metabolism and growth of kidney bean at flowering stage

Graphene oxide (GO) is a novel nanomaterial being applied in different fields, but was less used as foliar fertilizer in agriculture. We conducted a pot experiment to analyze the effects of foliar spraying GO from 0 (control), 50 (T₁), 100 (T₂), 150 (T₃) and 200 mg·L^-1 (T₄) on the morphogenesis and carbon and nitrogen metabolism of kidney bean plants during the initiation of flowering to clarify the physiological effects of foliar spraying GO. The results showed that dry matter accumulation, the content of photosynthetic pigments, soluble sugars of T₁ to T₄ treatments, were significantly increased by 40.7%-43.4%, 10.4%-80.7%, 6.4%-9.1% in kidney bean plants compared with CK treatment, respectively. T₃ treatment performed the best. Meanwhile, the activities of sucrose phosphate synthase, acid converting enzyme and neutral converting enzyme of T₃ and T₄ treatments were increased by 25.7%-45.5%, 17.4%-28.6%, and 14.7%-20.1%, and the activities of nitrate reductase, glutamine synthetase, and glutamate synthetase of T₂ and T₃ treatments were increased by 8.1%-15.2%, 11.5%-25.0%, and 89.7%-93.1%, respectively. In conclusion, foliar spraying of appropriate GO in early flowering stage of kidney bean could increase the content of photosynthetic pigments, improve the level of photosynthetic carbon and nitrogen metabolism, and increase dry matter accumulation. T₃ treatment (150 mg·L^-1) was the most effective in this study.