LAUSR

BACKGROUND Soybean is widely cultivated around the world, including regions with salinity conditions. Salt stress impairs plant physiology and growth, but recent evidence suggests that silicon (Si) is able to mitigate this stressful condition. Therefore, the purpose of this study was to evaluate how different strategies of Si application impact on salt stress tolerance of an intermediate-Si-accumulator species (soybean). Therefore, we applied four treatments: Si-untreated plants (Si 0); foliar spraying at 20 mM (Si F); nutritive solution addition at 2.0 mM (Si R), and combined foliar spraying at 20 mM plus nutritive solution at 2.0 mM (Si F + R). We investigate how Si application modified growth, leaf gas exchange, photosynthetic pigments, chlorophyll fluorescence, relative water content (RWC), nutrients accumulation, and ion homeostasis of soybean plants submitted to different levels of salt stress (50 and 100 mM of NaCl). RESULTS Salinity induced an expressive reduction in ion accumulation, plant water status, and growth of soybean, whilst Si application promoted contrary effects and increased potassium (K+ ) accumulation, water status, photosynthetic pigments content, chlorophyll fluorescence parameters, and gas exchange attributes. Additionally, Si application enhanced Si accumulation associated with decreased Na+ uptake and improved morpho-physiological growth. CONCLUSION The use of exogenous Si can be an efficient strategy to attenuate the harmful effects of salt stress in soybean plants. The best application method was observed with the combined foliar spraying with the presence of Si in the nutritive solution (Si F + R) strategy. This article is protected by copyright. All rights reserved.