NaCl胁迫对胡杨和新疆杨幼苗体内K+、Na+和Cl-分布的影响

采用盆栽沙培，研究了不同浓度NaCl处理下耐盐性不同的胡杨和新疆杨2种杨属物种幼苗体内K+、Na+和Cl-在器官间的区域化分布及其吸收运输特性，以揭示其耐盐性差异机制。结果表明：①NaCl胁迫下，2种植物体内K+含量下降，Na+和Cl-含量增加。不同器官中，K+含量叶中最高，茎中次之，根中最低；Na+含量由高到低依次为叶>根>茎；Cl-含量在2种植物间存在差异，胡杨叶中Cl-含量最高，根中次之，而新疆杨则是根中最高，叶中次之，但均是茎中最低。就各离子变化幅度而言，胡杨体内K+含量下降幅度及Na+增加幅度均低于新疆杨；胡杨根和茎中Cl-含量增加幅度小于新疆杨，而在叶中的增加幅度大于新疆杨。②2种植物体内K+/Na+值均随着NaCl浓度的升高而降低；除了低盐胁迫的茎以外，胡杨各器官中的K+/Na+值均显著高于新疆杨。与耐盐性较弱的新疆杨相比，胡杨根-茎运输选择性SK，Na值较低，而茎-叶运输选择性SK，Na值较高，根系截留Na+的能力较强。③随着NaCl浓度的增加，胡杨根向茎运输的SCl，Na值呈降低趋势，而新疆杨呈先降低后增加的趋势。耐盐性强的胡杨根向茎运输的SCl，Na值显著高于新疆杨，而茎向叶运输的SCl，Na值均低于新疆杨（2.0%NaCl处理除外）。以上结果表明，NaCl胁迫下胡杨是将盐分离子优先积累在根系来抵抗盐害，而新疆杨则是将盐分离子优先积累在茎部抵抗盐害。胡杨细胞拒盐性及液泡对盐分离子区隔化能力、维持K+、Na+平衡的能力较新疆杨强是其耐盐性优于新疆杨的主要原因。

Effect of NaCl Stress on K~+,N~a+ and Cl~- Allocation in Different Organs of Populus euphratica and Populus bolleana Lauche Seedlings

The uptake, transport and distribution of K+, Na+ and Cl- in different parts of Populus Euphratica and Populus bolleana Lauche seedlings under different NaCl stress conditions were investigated to study the salt tolerance mechanisms of the two poplar species. The results showed that: (1) The concentration of K+ declined, Na+ and Cl- increased in the two poplars under NaCl stress. The concentration of K+ showed the highest level in leaves, the less in stem and the lowest in root. The order of Na+ concentration was as follow: leaves > root > stem. The Cl- showed different distribution patterns between P. euphratica and P. bolleana, and the leaves contained more Cl- ion than in root for P. euphratica, however, the root contained more Cl- than in leaves for P. bolleana. The Cl- concentration was the lowest in the stem for the two poplar species. NaCl stress showed less effect in K+ and Na+ level in P. euphratica than in P. bolleana, and Cl- concentration increased less in P. euphratica root and stem than those of P. bolleana under NaCl stress. Compared with P. bolleana leaves, there was more significant Cl- level rise in P. euphratica leaves. (2) The K+/Na+ ratios in the two plants declined with the increasing of NaCl concentration. The K+/Na+ ratio was significantly higher in all organs of P. euphratica than that of P. bolleana except for stem exposed under low NaCl concentration. Compared with P. bolleana, P. euphratica had a lower transport selectivity of K+ to Na+ from root to stem, but had a higher transport selectivity of K+ to Na+ from stem to leaves, and retained more Na+ in roots. (3)With the increase of NaCl concentration, the transport selectivity of Cl- to Na+ from root to stem decresed in P. euphratica, but it decreased firstly and then increased in P. bolleana. Compared with P. bolleana, the transport selectivity of Cl- to Na+ from root to stem in P. euphratica was significantly higher, but the transport selectivity of Cl- to Na+ from stem to leaves was lower (except for 2% NaCl treatment). The results indicated that P. euphratica accumulated saline ions mainly in roots to resist salinity stress, while P. bolleana accumulated saline in stems. The salinity-resistant of P. euphratica was better than that of P. bolleana because the P. euphratica had better cell salinity-resistance, better compartmentalization of saline ions in cell vacuoles, and better maintenance of the K+/Na+ balance.