Enhancing the salt stress resistance of seeds and seedlings via a brassinolide sustained release agent system

Abstract Background The growing escalation of soil salinization is tremendously threatening the global food security and the development of sustainable agriculture. To address the worldwide predicament caused by salt stress toward crops, combining nanotechnology with the merits of plant hormone may become an efficient and effective approach. Results In this work, a sustained release agent system (BR@MSN) was developed by loading brassinolide (BR) to mesoporous silica nanoparticles (MSN) to enhance the salt stress resistance of cucumber seeds and seedlings. The obtained BR@MSN agent was about 120 nm. As an endogenous plant hormone, promotion in crop growth was found at low BR concentration. Due to the sustained release property, BR@MSN avoided excessive BR exposure to seeds and seedlings to cause inhibitory effects. After the soil application of BR@MSN, the promotion effect from BR combined with the regulation enhancement from MSN nanocarrier improved the seed germination rate by 11.76% under saline environment. Compared with the same BR concentration (2.0 mg/L), BR@MSN increased the seed germination rate even by 1324.29%. In addition, remarkable wettability on foliar surfaces was found, and the foliar application of BR@MSN significantly enhanced the salt stress resistance of cucumber seedlings by alleviating the accumulation of reactive oxygen species (ROS) and increasing the cell viability along with the improvement in superoxide dismutase (SOD) activity (234.11%), the decrease in malondialdehyde (MDA) content (61.30%), and the increase in chlorophyll content (110.88%). Conclusions The newly developed BR@MSN agents could effectively enhance the salt stress resistance of crop seeds and seedlings, and their applications significantly improved the seed germination rate and seedling growth. The remarkable efficacy makes this BR@MSN agent system potential in agricultural field for enhancing the salt stress resistance of crops and facilitating the development of sustainable agriculture. Graphical Abstract