短期NaCl胁迫对不同小麦品种幼苗K+吸收和Na+、K+积累的影响

为研究盐胁迫下小麦幼苗生长及Na⁺、K⁺的吸收和积累规律,以中国春、洲元9369和长武134等3种耐盐性不同小麦品种为材料,采用非损伤微测技术检测盐胁迫2 d后的根系K⁺离子流变化,并对植株体内的Na⁺、K⁺含量进行测定。结果表明:短期(2d)盐胁迫对小麦生长有抑制作用,且对根系的抑制大于地上部,耐盐品种下降幅度小于盐敏感品种。盐胁迫下,小麦根际的 K⁺大量外流,盐敏感品种中国春K⁺流速显著高于耐盐品种长武134,最高可达15倍。小麦幼苗地上部分和根系均表现为Na⁺积累增加,K⁺积累减少,Na⁺/K⁺比随盐浓度增加而上升。中国春限Na⁺能力显著低于长武134,Na⁺/K⁺则显著高于长武134。综上所述,盐胁迫下造成小麦组织器官中Na⁺/K⁺比上升的主要原因是根系K⁺大量外流和Na⁺的过量积累,耐盐性不同的小麦品种间差异显著,并认为根系对K⁺的保有能力可能是作物耐盐性评价的一个重要指标。

Effect of short-term salt stress on the absorption of K+ and accumulation of Na+,K+ in seedlings of different wheat varieties

Salinity is a major abiotic stress affecting agricultural production. Salinity tolerance in glycophytes is mainly associated with the ability to maintain high K⁺:Na⁺ ratios in shoots. The ability of the plant to exclude uptake of sodium (Na⁺) and to retain potassium (K⁺) in the cells may contribute to this trait. To better understand the accumulation and transport of salinity ions in wheat under high-salt conditions, we examined responses of plant roots under saline conditions using three varieties of wheat with varying levels of salt tolerance; Chinese-Spring, ZhouYuan-9369, and ChangWu-134. We examined seedling growth, absorption of K⁺, and accumulation of both Na⁺ and K⁺ under salt stress. The non-invasive micro-test technique (NMT) was adapted to detect the K⁺ flux in the roots and to determine Na⁺ and K⁺ contents of shoots and roots after 2 days of salt stress. The advantages of the non-invasive micro-test technique over traditional methods are that it is rapid, non-invasive, and it can be used on live plants. For all varieties, the growth of wheat seedlings was inhibited by salt stress, and the salt-tolerant cultivar ChangWu-134 maintained higher dry weight than the other two varieties. In all three varieties, roots were more strongly inhibited than shoots under salt stress. The efflux velocity of K⁺ in roots was nearly 15 times greater in Chinese-Spring than in ChangWu-134 under saline conditions. This result was consistent with those obtained using traditional methods, which showed that the K⁺ contents in shoots and roots decreased under salt stress. During salt stress, the Na⁺ contents in shoots and roots increased while the K⁺ contents decreased, resulting in an increase in the Na⁺:K⁺ ratio. Among the three varieties, Changwu-134 showed the lowest concentration of Na ⁺ in cells of seedlings under salt stress. The Na⁺:K⁺ ratios in shoots and roots were higher in Chinese-Spring than in ChangWu-134, suggesting that the salt-tolerant cultivar ChangWu-134 showed greater Na⁺-exclusion capability than the salt-sensitive cultivar Chinese-Spring. More closely related indices of salinity tolerance have been proposed, such as Na⁺ and K⁺ concentrations and K⁺/Na⁺ tissue content ratios in shoots or roots, or the production of specific metabolites in various species. Among the three wheat varieties, the Na⁺ restriction capability was highest in Changwu-134. This indicates that Changwu-134 was able to increase accumulation of Na⁺ in the roots and decrease the transportation of Na⁺ to the shoots as mechanisms to tolerate salinity. Thus, improving the ability of plants to accumulate salinity ions and control their transport should produce cultivars with even greater salt tolerance. In conclusion, under salt stress, the significant increase in the velocity of K⁺ efflux and the accumulation of Na⁺ resulted in increased Na⁺:K⁺ ratios in roots and shoots. Moreover, the Na⁺:K⁺ ratio differed between salt-tolerant and salt-sensitive wheat cultivars. In wheat, it appears that the capacity to retain K⁺ is an important indicator of salt tolerance, and the non-invasive micro-test technique should be a reliable screening method to select salt-tolerant cultivars in plant breeding programs.