Wild barley Hordeum spontaneum (WB) is the progenitor of a cultivated barley Hordeum vulgare (CB). Understanding efficient mechanisms evolved by WB to cope with abiotic stresses may open prospects of transferring these promising traits to the high yielding CB genotypes. This study aimed to investigate the strategies that WB plants utilise in regard to the control of stomatal operation and ionic homeostasis to deal with salinity stress, one of the major threats to the global food security. Twenty-six genotypes of WB and CB were grown under glasshouse conditions and exposed to 300 mM NaCl salinity treatment for 5 weeks followed by their comprehensive physiological assessment. WB had higher relative biomass than CB when exposed to salinity stress. Under saline conditions, WB plants were able to keep constant stomatal density (SD) while SD significantly decreased in CB. The higher SD in WB also resulted in a higher stomatal conductance (gs) under saline conditions, with gs reduction being 51% and 72% in WB and CB, respectively. Furthermore, WB showed faster stomatal response to light, indicating their better ability to adapt to changing environmental conditions. Experiments with isolated epidermal strips indicated that CB genotypes have the higher stomatal aperture when incubated in 80 mM KCl solution, and its aperture declined when KCl was substituted by NaCl. On the contrary, WB genotype had the highest stomatal aperture being exposed to 80 mM NaCl suggesting that WB plants may use Na+ instead of K+ for stomata movements. Overall, our data suggest that CB employ a stress-escaping strategy by reducing stomata density, to conserve water, when grown under salinity conditions. WB, on a contrary, is capable of maintaining relatively constant stomata density, faster stomatal movement and higher gs under saline conditions.

中文翻译：

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气孔性状是野生大麦优良耐盐性的决定因素

野生大麦Hordeum spontaneum (WB) 是栽培大麦Hordeum vulgare (CB) 的祖先。了解 WB 进化出的应对非生物胁迫的有效机制可能会打开将这些有前途的性状转移到高产 CB 基因型的前景。本研究旨在调查 WB 植物在控制气孔操作和离子稳态方面所采用的策略，以应对盐胁迫，这是对全球粮食安全的主要威胁之一。WB 和 CB 的 26 种基因型在温室条件下生长，并暴露于 300 mM NaCl 盐度处理 5 周，然后进行全面的生理评估。当暴露于盐度胁迫时，WB 具有比 CB 更高的相对生物量。在盐碱地条件下，WB 植物能够保持恒定的气孔密度 (SD)，而 CB 中的 SD 显着降低。WB 中较高的 SD 还导致在盐水条件下更高的气孔导度 (gs)，在 WB 和 CB 中，gs 减少分别为 51% 和 72%。此外，WB 对光表现出更快的气孔反应，表明它们更好地适应不断变化的环境条件。分离表皮条带实验表明，CB 基因型在 80 mM KCl 溶液中培养时具有较高的气孔孔径，而当 KCl 被 NaCl 替代时其孔径减小。相反，WB 基因型在暴露于 80 mM NaCl 时具有最高的气孔孔径，这表明 WB 植物可能使用 Na+ 而不是 K+ 进行气孔运动。全面的，我们的数据表明，当在盐度条件下生长时，CB 采用了一种通过降低气孔密度来节省水分的压力逃避策略。相反，WB 能够在盐水条件下保持相对恒定的气孔密度、更快的气孔运动和更高的 gs。