The response of wildtype and mutant cultivars of soybean to salt stress - comparing vegetative and reproductive phases on the basis of leaf biochemical contents, RWC, and stomatal conductance

Soybean, as a major oilseed crop, is cultivated in many parts of the world including saline-affected regions. A four-replicated factorial experiment based on a completely randomized design with five salinity levels (control, 50, 100, 150, and 200 mM NaCl) and five wild-type and new mutant cultivars of soybean (Williams, Clark, M-4, M-7, and M-9) was done at two vegetative and reproductive phases to study leaf oxidants, antioxidants and osmolytes under salinity stress. The vegetative phase demonstrated higher K⁺:Na⁺ ratio, cell membrane stability, relative water content (RWC) and stomatal conductance to H₂O (gs) accompanied with lower oxidative stress, antioxidants and osmolytes contrasting to reproductive phase. At both phenological phases, saline stress stimulated antioxidative defense owing to the enhancement of oxidative stress. The results indicated that mutants possessed a better antioxidative system than their wild-types.

大豆作为重要油料作物，在全球诸多区域均有种植，其中亦涵盖盐渍化区域。本研究采用完全随机设计的四重复析因试验，设置5个盐分梯度（对照组、50、100、150、200 mM NaCl）与5个大豆野生型及新型突变体品种（Williams、Clark、M-4、M-7、M-9），分别在营养生长与生殖生长两个物候期开展试验，以探究盐胁迫下大豆叶片的氧化物质、抗氧化成分及渗透调节物质。与生殖生长阶段相比，营养生长阶段的钾钠比（K⁺:Na⁺）、细胞膜稳定性、相对含水量（relative water content, RWC）及水汽气孔导度（stomatal conductance to H₂O, gs）均显著更高，而氧化胁迫水平、抗氧化物质含量与渗透调节物质水平则显著更低。在两个物候期内，盐胁迫均通过加剧氧化胁迫激活了抗氧化防御系统。研究结果表明，大豆突变体的抗氧化系统性能优于其野生型亲本。