盐胁迫下胡杨和毛白杨叶细胞中的离子区隔化

该文以抗盐的胡杨和盐敏感的毛白杨组培再生苗为实验材料,利用X--射线微区分析技术研究盐胁迫下(为期20d的盐处理)叶片各种类型细胞内主要元素Na+、Cl-、K+的分布情况,测定的细胞类型包括:①叶脉细胞(叶脉维管束导管、叶脉维管束内部和外部的薄壁细胞);②叶肉细胞(栅栏组织、海绵组织);③表皮细胞(上、下表皮细胞).结果表明,胡杨和毛白杨叶细胞对盐离子的区隔化有明显差异:与毛白杨相比,盐处理后的胡杨叶细胞不但具有较高的拒Na+能力,即将Na+贮存在质外体中,而且液泡区隔Na+的能力也强于毛白杨.在Cl-的区隔化方面,对照处理胡杨各种类型的细胞(包括叶脉、叶肉和表皮细胞)Cl-浓度都高于毛白杨,但在盐胁迫下,胡杨叶片的细胞壁、液泡甚至叶绿体中Cl-的含量都低于毛白杨,这是胡杨根细胞限制Cl-离子根冠运输的结果.盐处理使胡杨叶片各种类型细胞中的K+浓度降低;与胡杨不同,毛白杨叶片细胞中质外体的K+浓度下降,而液泡中的K+水平却相应提高,这是毛白杨细胞内K+重新分配的结果:由于盐处理后毛白杨液泡内积累了过多的Cl-,K+从细胞壁进入液泡,用以平衡液泡内Cl-积累所带来的负电荷.

Ion compartmentation in leaf cells of Populus euphratica and P.tomentosa under salt stress

The authors used X-ray microanalysis to investigate ion compartmentation (Na~+, Cl~-and K~+) in leaf cells of a salt_tolerant species, Populus euphratica and a salt_sensitive species, P. tomentosa(treated by salt for 20 days). Regenerated plants were used in this experiment and following types of leaf cells were examined: 1) leaf vein cells—including xylem vessels in the bundle, parenchyma cells in the bundle and around the bundle; 2) mesophyll cells—including palisade and spongy mesophyll cells; 3) epidermal cells—including adaxial and abaxial epidermis. Results showed that there was genotypic difference in subcellular ion compartmentation under salt stress. Compared with P. tomentosa, P. euphratica exhibited a greater ability to exclude Na~+ to the apoplast, furthermore, P. euphratica had a higher capacity to compartmentize Na~+ into vacuoles. Control plants of P. euphratica retained higher levels of Cl~-in all cell compartments (chloroplast, cell wall and vacuole), as compared to the control of P. tomentosa plants. However, stressed P. euphratica remained lower levels of Cl~-than salinised P. tomentosa in all types of leaf cells, this was the result of root-to-shoot salt transport restriction in P. euphratica under saline conditions. With regard to K~+, salinity reduced K~+ level in chloroplast, vacuole and cell wall of all types of leaf cells in P. euphratica with a few exceptions. Unlikely, K~+ levels in the apoplast of P. tomentosa were lowered by salinity, but in vacuole, K~+ increased in response to salt stress. This was presumably resulted from the redistribution of K~+ in cell compartments: K~+ fluxed from the cell wall into the vacuole, which was favorable to balance the negative charges caused by vacuolar Cl~-compartmentation.