Institute of Biology, Ufa Scientific Center , Russian Academy of Sciences , pr. Oktyabrya 69, Ufa 450054 , Russia.
AoB Plants. 2010;2010:plq006. doi: 10.1093/aobpla/plq006. Epub 2010 May 16.
Certain lines of wild barley (Hordeum spontaneum) are more tolerant of salinity than others. The physiological basis of this difference is examined in a comparative study of a saline-tolerant and saline-intolerant line that emphasizes plant water relations.
Effects of salt-treatment (75 mM maximum) extending from a few hours to 3 weeks were quantified in 8-day-old seedlings of a saline-sensitive wild barley line ('T-1') and a less saline-sensitive line ('20-45'). Plants were grown in nutrient culture. Levels of mRNA of the HtPIP2;4 aquaporin (AQP) gene were determined together with a range of physiological responses including root hydraulic conductivity, osmotic potential of root xylem sap, transpiration, leaf relative water content, root water content, leaf water potential, leaf sap osmolality, leaf length, leaf area and chlorophyll content.
Salt treatment inhibited transpiration and hydraulic conductivity more in salt-tolerant '20-45' plants than in salt-sensitive 'T-1'. In '20-45', the effect was paralleled by a fast (within a few hours) and persistent (3 days) down-regulation of aquaporin. In salt-sensitive 'T-1' plants, aquaporin down-regulation was delayed for up to 24 h. Greater tolerance in '20-45' plants was characterized by less inhibition of leaf area, root fresh weight, leaf water content and chlorophyll concentration. Leaf water potentials were similar in both lines.
(i) Decline in hydraulic conductivity in salt-treated barley plants is important for stomatal closure, (ii) lowered transpiration rate is beneficial for salt tolerance, at least at the seedling stage and (iii) changes in AQP expression are implicated in the control of whole plant hydraulic conductivity and the regulation of shoot water relations.
某些野生大麦（Hordeum spontaneum）品系比其他品系更能耐受盐度。本研究通过对耐盐和不耐盐品系的比较研究，重点研究植物水分关系，探讨了这种差异的生理基础。
在为期 8 天的盐敏感野生大麦品系（‘T-1’）和耐盐性稍差的品系（‘20-45’）幼苗中，定量研究了从几小时到 3 周的盐处理（最大 75 mM）的影响。植物在营养培养中生长。测定 HtPIP2；4 水通道蛋白（AQP）基因的 mRNA 水平以及一系列生理响应，包括根水力传导度、木质部汁液渗透压、蒸腾、叶片相对含水量、根含水量、叶片水势、叶片汁液渗透压、叶片长度、叶面积和叶绿素含量。
盐处理在耐盐‘20-45’植物中比在盐敏感‘T-1’植物中更能抑制蒸腾和水力传导度。在‘20-45’中，这种效应伴随着水通道蛋白的快速（数小时内）和持久（3 天）下调。在盐敏感‘T-1’植物中，水通道蛋白的下调延迟了长达 24 小时。在‘20-45’植物中，更大的耐受性表现为叶片面积、根鲜重、叶片含水量和叶绿素浓度的抑制较小。两条线的叶片水势相似。
（i）盐处理大麦植物水力传导度的下降对气孔关闭很重要，（ii）降低蒸腾速率有利于耐盐性，至少在幼苗阶段如此，（iii）AQP 表达的变化与控制整株植物水力传导度和调节地上部水分关系有关。
