盐胁迫下盐草和高羊茅营养器官的离子微区分布

The Micro-Distribution of Elements in Distichlis spicata and Festuca arundinacea Under Salt Stress

【目的】探讨植物耐盐性和盐胁迫下植物不同营养器官离子微区分布特性之间的关系。【方法】采用扫描电镜和X射线能谱仪联用,对250mmol·L-1 NaCl胁迫20d的盐草(盐生植物)和高羊茅(甜土植物)的营养器官进行了点扫描和离子分布测定。【结果】盐胁迫下,盐草和高羊茅根组织中Na+和Cl-的相对重量都很高,但是高羊茅中柱层中的Na+和Cl-相对重量都高于盐草;和高羊茅相反,在盐草茎中,大量的Na+分布在韧皮部中,而Cl-则主要存在于木质部中;而高羊茅叶组织中Na+相对重量是盐草叶组织中2倍。【结论】盐胁迫下盐草和高羊茅根尖表皮、皮层和中柱细胞Na+和Cl-较高,而K+含量较低,这说明盐草可通过根组织对离子的选择性吸收降低进入植物体的有害离子量,并通过离子在茎中的再次分配降低有害离子进入叶组织,从而避免对叶组织的较大离子毒害。

[Objective] The objective of this paper is to investigate the relationship between the salt-tolerance and the microdistribution of mineral ions in roots, stems and leaves of Distichlis spicata and Festuca arundinacea under salt stress. [Method] Distichlis spicata （halophyte） and Festuca arundinacea （glycophyte） were grown hydroponically with 250mM NaCl. Root tips, stems, and leaves were harvested for microanalysis 20 days after transplanting. Using an energy dispersive X-ray microanalyzer （EDX）, the X-ray percentage of atom content and the peak of X-ray energy spectra intensity were measured. [Result] It was shown that high Cl^- and Na^＋ X-ray peaks were recorded in root tissues regardless olD. spicatar and F. arundinacea, but X-ray percentages of Na^＋ and Cl^- content in root stelar cells ofF. arundinacea were higher than in D. spicata. While comparable, the higher percentage of Na^＋ content existed in the stem xylem, and higher percentage of Cl^- content distributed in the stem phloem in D. spicata than in F. arundinacea. The concentration of Na^＋ in leaves ofF. arundinacea was 2 times more than in leaves ofD. spicata [ Conclusion ] Distichlis spicata regulated toxic ion absorption by the mechanism of selective absorption in roots, and recirculated Na^＋ back to roots by phloem or retrieval Na^＋ from xylem. Thus less toxic ion was transported to leaf tissue. Therefore the microdistribution of mineral ions in plants was involved in salt tolerance.