Effects of Graphene on Yield, Grain Quality, 2-AP Biosynthesis and Antioxidant Systems of Fragrant Rice

Abstract

The application of nanotechnology in agricultural neighborhoods is rapidly developing with the aim of promoting growth and enhancing crop tolerance to environmental stresses. However, there are fewer reports on the application of graphene nanoparticles in practical production, especially in fragrant rice. In early-season and late-season pot experiments conducted in 2022, the effects of graphene on the yield, grain quality, 2-acetyl-1-pyrroline (2-AP) and antioxidant systems of two fragrant rice cultivars (19× and Meixiangzhan) were examined at concentrations of 9 g/hm2, 18 g/hm2 and 27 g/hm2. The results showed that graphene T1 treatment at 9 g/hm2 significantly increased the activity of PDH and P5CS, promoted the synthesis of proline and P5C and significantly increased the 2-AP content of the grains of the two fragrant rice cultivars by 10.33–39.88% and 22.05–65.76%, respectively, in both growing seasons. Meanwhile, the lower concentration of T1 treatment (9 g/hm2) increased the grains per panicle and 1000-grain weight, enhancing the grain yield of both fragrant rice cultivars. The T1 treatment (9 g/hm2) had significant effects on the appearance and nutritional quality of both fragrant rice cultivars. It increased the head rice rate and protein content of the grains while also increasing the amylose content of 19× and reducing the chalkiness degree of 19×. Conversely, the T1 treatment reduced the amylose content and increased the chalkiness degree of Meixiangzhan. In addition, the low concentration of T1 treatment significantly increased the POD and SOD activities, increased the content of photosynthetic pigments and decreased the content of MDA in the leaves. However, 18 g/hm2 and 27 g/hm2 had slightly negative effects on yield, grain quality and fragrance biosynthesis in both fragrant rice cultivars. Furthermore, the results of structural equation modeling showed that antioxidant enzymes had a significant, positive effect on the grain’s 2-AP content and 2-AP synthesis-related enzyme activity, and photosynthetic pigments had a significant, positive effect on yield and grain appearance quality, while rice appearance quality and nutritional quality had significant, positive effects on yield. Overall, this study showed that suitable concentrations of graphene have good potential for use in fragrant rice production, but additional attention should be paid to the concentration of graphene application.