盐胁迫对灌木柳体内离子分布的影响

Effects of salt stress on ionic distribution of shrub willow

以2个耐盐性不同的灌木柳为材料,采用营养液水培,用100 mmol·L-1Na Cl处理幼苗10 d,研究盐胁迫下离子在器官、组织和细胞水平上区域化分布的特性。结果表明:(1)Na Cl胁迫下,灌木柳植株体内K^+含量下降,Na^+和Cl^-含量升高;不同器官间,茎中Na^+和Cl^-含量最高,叶中Na^+和Cl^-含量最低;根向茎运输SK,Na值降低,茎向叶运输SK,Na值提高。(2)与耐盐性较弱的JW2367相比,耐盐性较强的JW2345 SK,Na值变化幅度较大,茎对Na^+的截留作用较强,而叶片中Na^+积累较少,且K^+含量下降幅度较小,说明离子区域化分布的调控能力相对较强,是JW2345耐盐性较强的主要原因之一。(3)对耐盐型JW2345根、茎和叶片横切面进行X射线微区分析表明,盐胁迫下Na^+、K^+和Cl^-在根各组织间均呈均匀分布;在茎中,与对照相比,髓部Na^+、Cl^-升高幅度明显高于周皮和微管组织;叶片栅栏组织中Na^+、Cl^-相对含量增幅最小,且K^+相对含量明显高于表皮和海绵组织。(4)盐胁迫下JW2345茎髓部细胞内离子分布结果显示,液泡对Na^+和Cl^-具有明显的区隔化作用,表明柳树茎髓细胞水平上离子区隔化分布是避免细胞受盐分毒害的重要机制。

To study the compartmentalized ion distribution in the seedlings of two clones with salt-tolerance, we treated seedlings of shrub willow with 100 mmol·L-1 Na Cl for 10 d by the method of hydroponics. The results showed that under Na Cl stress, K^＋ content decreased in the seedlings, while Na^＋ and Cl^- contents increased in salinity. Among the test organs, stems had the highest content of Na^＋and Cl^-, while leaves had the lowest. The transportation selectivity of K^＋ to Na^＋ from root to stem declined, and transportation selectivity of K^＋ to Na^＋ from stem to leaf increased. Compared with salt-susceptible clone JW2367, salt-resistant clone JW2345 had a bigger change range of transportation selectivity of K^＋ to Na^＋ from root to stem and of K^＋ to Na^＋ from stem to leaf, and retained more Na^＋ in root; while accumulated more K^＋ and less Na^＋ in its leaves. All of these suggested that the stronger adjustment ability of the compartmentalized ion distribution was the main reasons for the stronger salt-tolerance of JW2345. Analysised with X-ray electron probe microanalysis, we fined the ion content somewhat differed with different tissues. Na^＋, K^＋ and Cl^- were almost distributed uniformly in all tissues of roots, while in stems, pith cells had the greatest increment of Na^＋ and Cl^-,followed by vascular tissue cells and periderm cells. In leaves,palisade tissue cells had the smallest increment of Na^＋ and Cl^- and the relative content of K^＋ in palisade tissue cells was higher than that in spongy cells and epidermal cells.The accumulation of Na^＋ and Cl^- in the vacuolar was much higher than that in the cytoplasm in the cells of stem pith,and the compartmentalized distribution of ions in the cells of stem pith was also one of physiological adaptation mechanisms of shrub willow to salinity.