钙胁迫对白枪杆幼苗生长及矿质离子代谢的影响

Effect of calcium stress on growth and mineral ion metabolism of Fraxinus malacophylla seedlings

【目的】研究CaCl_(2)胁迫下白枪杆幼苗的生长及其矿质离子吸收、运输和分配特征,揭示白枪杆对石漠化岩溶地区高钙环境的离子适应机制。【方法】以1年生白枪杆幼苗为研究试材,用CaCl_(2)模拟钙胁迫处理,分别设置对照(0 mmol/L CaCl_(2),CK)、低钙(25 mmol/L CaCl_(2))、中钙(50 mmol/L CaCl_(2))和高钙(75 mmol/L CaCl_(2))4个处理,通过分析根、茎、叶生物量(干质量)和根冠比,以及根、茎、叶中的Na^(+)、K^(+)、Ca^(2+)、Mg^(2+)离子含量及其对K^(+)、Ca^(2+)、Mg^(2+)离子的吸收和选择性运输能力,探究钙胁迫处理对白枪杆幼苗生长和根、茎、叶中矿质离子分配、吸收与运输的影响。【结果】低、中、高钙胁迫下,白枪杆幼苗生长均受到一定程度的抑制,生物量下降,根冠比增加,其中25~50 mmol/L CaCl_(2)胁迫下各器官生物量表现为叶>根>茎,75 mmol/L胁迫下则表现为根>叶>茎。随钙胁迫程度的加剧,白枪杆幼苗叶、根中的Na^(+)含量显著降低,茎中Na^(+)含量明显增加;K^(+)在叶、根中的含量有所增加,但主要积累根中;Ca^(2+)、Mg^(2+)主要积累在叶中,随钙胁迫加重叶中的Ca^(2+)含量递增,Mg^(2+)含量则以50 mmol/L CaCl_(2)处理下最高。叶中的K^(+)/Na^(+)值与Ca^(2+)/Na^(+)值随钙胁迫加重总体均呈上升趋势,茎、根中的K^(+)/Na^(+)值及各器官中的Mg^(2+)/Na^(+)值均以50 mmol/L CaCl_(2)处理下最高。钙胁迫下,根向叶运输K^(+)及向茎运输Ca^(2+)、Mg^(2+)能力下降,根、茎向叶运输Ca^(2+)、Mg^(2+)能力上升。【结论】白枪杆幼苗通过调节各器官生物量和离子分配适应钙的胁迫,主要通过茎对Na^(+)的截留减少Na^(+)对叶片的毒害,以维持叶片的正常生理功能,同时其对高钙生存环境的适应能力也与Ca^(2+)、Mg^(2+)的选择性运输能力增强有关。

【Objective】 This study investigated the growth of Fraxinus malacophylla seedlings and absorption,transport,and distribution characteristics of mineral ions under CaCl_(2) stress to reveal the ion ada-ptation mechanism of F.malacophylla in high-calcium environments in karst rocky desertification areas.【Method】 One-year-old F.malacophylla seedlings were treated using CaCl_(2) to simulate calcium stress in four treatments of control(0 mmol/L CaCl_(2),CK),low calcium(25 mmol/L CaCl_(2)),medium calcium(50 mmol/L CaCl_(2)),and high calcium(75 mmol/L CaCl_(2)).The effects of calcium stress on growth of F.malacophylla seedlings and distribution,absorption,and transportation characteristics of mineral ions in roots,stems,and leaves were explored by analyzing contents of Na^(+),K^(+),Ca^(2+),and Mg^(2+)ions in roots,stems,and leaves,and their ability to absorb and selectively transport K^(+),Ca^(2+),and Mg^(2+) ions.【Result】 Under calcium stress,the growth of F.malacophylla seedlings was inhibited to a certain extent,resulting in decreased biomass and increased root-to-shoot ratio.The biomass under 25-50 mmol/L CaCl_(2) stress was in the decreasing order of leaves>roots>stems,while the order was roots>leaves>stems under 75 mmol/L stress.With increasing calcium stress,Na^(+) content in leaves and roots of F.malacophylla seedlings decreased significantly,while that in stems increased.K^(+) content increased in leaves and roots,but mainly accumulated in roots.Ca^(2+) and Mg^(2+) mainly accumulated in leaves,and Ca^(2+) content increased with the increase of calcium stress,reaching the highest level at 50 mmol/L CaCl_(2).K^(+)/Na^(+) and Ca^(2+)/Na^(+) ratios in leaves showed an overall increasing trend with increasing calcium stress.K^(+)/Na^(+) ratio in stems and roots and Mg^(2+)/Na^(+) ratio in all organs reached the highest level in 50 mmol/L CaCl_(2) treatment.Under calcium stress,the transport capacity of K^(+) from roots to leaves and that of Ca^(2+) and Mg^(2+) from roots to stems decreased,while that of Ca^(2+) and Mg^(2+) from roots and stems to leaves increased.【Conclusion】 F.malacophylla seedlings adapted to calcium stress by adjusting biomass and ion distribution in various organs.They mainly reduce Na^(+) toxicity to leaves by trapping Na^(+) in stems,thereby maintaining normal physiological functions of leaves.The adaptation to high-calcium environments was also related to enhanced selective transport of Ca^(2+) and Mg^(2+).