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.

This study evaluated the effects of soil moisture deficit and subsequent watering on the growth of Bromus inermis Leyss., Dactylis glomerata L., Lolium perenne L. and Phleum pratense L. under a non-heat-stressed condition. Plants grown in pots were exposed either to a dry or control soil condition (irrigated 30 and 80 g water kg 1 soil, respectively) at 10.320.2 degrees C for 38 days (drought treatment phase), and thereafter to the control soil condition for 27 days (recovery phase). D. glomerata maintained relative water content (RWC) during the drought treatment with the greatest depression in the growth and physiology (photosynthesis and transpiration), suggesting a relatively high ability of dehydration postponement as a drought adaptation mechanism. By contrast, B. inermis showed the smallest growth depression during the drought treatment despite the reduction in RWC, indicating a relatively high ability of dehydration tolerance. During the drought treatment, L. perenne and P. pratense showed similar degrees of growth depression, which was lighter than that in D. glomerata. However, the growth of P. pratense was still strongly depressed as compared with the control during the recovery phase, whereas that of L. perenne received no after-effect of the preceding dry treatment, which demonstrated a relatively low ability of dehydration recovery in P. pretense. The results show that L. perenne has higher overall drought tolerance than P. pratense and D. glomerata.