ABSTRACT Saline‐alkali stress, a widespread abiotic stress worldwide, severely affects the growth, development, and yield formation of crops. Nanomaterials show great potential in regulating plant growth and improving stress resistance due to their unique physical and chemical characteristics. In this study, nano‐silicon dioxide (nano‐SiO 2 ) was prepared by the sol–gel method and used to construct a highly efficient melatonin delivery system. Soybean cultivars Hefeng 50 and Henong 95 were field‐grown in saline‐alkali soil and foliar‐sprayed with 200 mg/L nano‐SiO 2 , 300 μM melatonin (MT), or their combination at the V3 stage. In the melatonin–nano‐SiO 2 system, the encapsulation efficiency and drug‐loading capacity of melatonin by nano‐SiO 2 were 35% and 53%, respectively. The system can significantly enhance melatonin photostability. The melatonin–nano‐SiO 2 treatment significantly enhanced the antioxidant enzyme activity and regulated glutathione levels in soybean plants and reduced the accumulation of reactive oxygen species. The results of physiology, RNA‐seq, and qRT‐PCR indicated that melatonin–nano‐SiO 2 treatment can repair photosynthetic carbon metabolism damage induced by saline‐alkali stress. Specifically, it increased leaf area, photosynthetic pigment content, photosystem II (PSII) efficiency, and gas exchange parameters of leaves. It also promoted the activities of sucrose phosphate synthase (SPS) and sucrose synthase (SuSy), while inhibiting the activities of α ‐amylase and β ‐amylase, thereby enhancing soluble sugar, sucrose, and starch accumulation. Ultimately, melatonin–nano‐SiO 2 treatment significantly improved pod number per plant, seed number per plant, and 100‐seed weight. Compared to saline‐alkali stress, the per plant yield of HF50 and HN95 under melatonin–nano‐SiO 2 treatment increased by 77.41% and 76.52%, respectively.
Jianing et al. (Fri,) studied this question.