Abstract
Salinity episodes that are common in arid regions, characterized by dryland, are adversely affecting crop production worldwide. This study evaluated the effectiveness of brassinolide (BL) in ameliorating salinity stress imposed on soybean at four levels (control (1.10), 32.40, 60.60 and 86.30 mM/L NaCl) in factorial combination with six BL application frequency (control (BL0), application at seedling (BL1), flowering (BL2), podding (BL3), seedling + flowering (BL4) and seedling + flowering + podding (BL5)) stages. Plant growth attributes, seed yield, and N, P, K, Ca and Mg partitioning to leaves, stems and roots, as well as protein and seed-N concentrations, were significantly (p ≤ 0.05) reduced by salinity stress. These trends were ascribed to considerable impairments in the photosynthetic pigments, photosynthetically active radiation, leaf stomatal conductance and relative water content in the leaves of seedlings under stress. The activity of peroxidase and superoxidase significantly (p ≤ 0.05) increased with salinity. Foliar spray with BL significantly (p ≤ 0.05) improved the photosynthetic attributes, as well as nutrient partitioning, under stress, and alleviated ion toxicity by maintaining a favourable K+/Na+ ratio and decreasing oxidative damage. Foliar spray with brassinolide could sustain soybean growth and seed yield at salt concentrations up to 60.60 mM/L NaCl.
Highlights
Abiotic stresses such as salinity, heat, drought, acidity, and waterlogging cause severe damages to crop production
We explored the effectiveness of BL on ameliorating the salinity effect on soybean at morphological and physiology levels, as well as yield responses
Salinity stress is a significant constraint to the growth and development of soybean plants in arid regions
Summary
Abiotic stresses such as salinity, heat, drought, acidity, and waterlogging cause severe damages to crop production. Soil salinity (a major threat to crop production across the globe) affects various plant physiological activities through increased oxidative damage, decreased turgor, as well as changes in leaf gas exchange [1], leading to reduced plant growth, development and yield [2,3]. Increased salinity alters the plants’ morphology, physiology and metabolism through increased ion toxicity that leads to decreases in the availability of essential elements such as phosphorus and calcium, as well as protein synthesis and metabolism of lipids [9]. These result in premature senescence and the loss of photosynthetic efficiency that lead to reductions in carbon assimilation and yield. Plants have the capacity to generate various forms of antioxidants that can alleviate oxidative damages, there is a need to further investigate other exogenous applications, including the use of phytoprotectants such as brassinolide (BL), to boost plants’ oxidative defence against salinity stress
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