碱蓬和滨藜对镉和钠吸收、转运及亚细胞分布特性的比较研究

Uptake, Translocation and Subcellular Distribution Characteristics of Cadmium and Sodium in Suaeda salsa and Atriplex triangularis

采用水培试验方法,比较了不同类型盐生植物碱蓬和滨藜的Cd耐性,研究了两者对Cd和Na的富集规律及亚细胞水平上的Cd解毒机制差异。结果表明,Cd胁迫下碱蓬和滨藜的根长、株高及干重等均受到不同程度的抑制,两者的表观毒害症状及对Cd的响应敏感度也存在明显差异;根系耐性指数可以作为评价两者Cd耐性的指标,碱蓬表现出更强的Cd耐性。另外,除1μmol·L-1Cd胁迫下,碱蓬根表的单位面积Cd吸附量均显著高于滨藜;两者吸收的Na大量转运至地上部,吸收的Cd则主要富集在根部,但碱蓬对Cd的转运能力比滨藜弱。亚细胞分布分析发现,两种盐生植物各器官中Cd均主要分布于细胞壁,其次为胞液;细胞壁的固定为两者亚细胞水平上的主要Cd解毒机制,且碱蓬不同器官细胞壁的固定能力比滨藜强,根部Cd亚细胞分布特性对Cd从根部向地上部转运有显著影响。Cd胁迫除产生直接毒害外,也影响碱蓬和滨藜地上部及根部的Na含量,干扰了两者不同器官及亚细胞水平上的正常Na稳态。

Tolerance and accumulation of cadmium in halophytic species are important for phytoremediation and food safety of heavy metals contaminated saline soils. A hydroponic experiment was conducted to compare the growth response and the Cd and Na uptake, translocation and subcellular distribution of two halophytic species, Suaeda salsa and Atriplex triangularis, in order to improve the understanding of Cd accumulation and detoxification mechanisms at the subcellular level of these two types of halophytes. Both species showed decrease in root length, plant height and biomass under Cd stress. However, the growth response and Cd toxicity symptoms were quite different between both species, with S. salsa less severely affected by Cd stress than A. triangularis, implying that S. salsa had higher Cd tolerance than A. triangularis did. The capacity of Cd adsorption on root surface of two halophytes was also obviously different. Additionally, S. salsa had higher root Cd accumulation but a lower Cd translocation rate than A. triangularis. Cadmium tolerance was associated with the Cd accumulation in the roots and thus low transport to the shoots. The subcellular distribution of Cd was in order of cell wall fraction >soluble fraction >organelle fraction. The cell wall and soluble fractions were the dominant storage compartments for Cd in the roots, stems and leaves. S. salsa could bind more Cd in the cell wall fractions than A. triangularis. Thus, immobilization of Cd by the cell walls of different organs appeared to be the main Cd detoxification mechanism at the subcellular level. Cadmium stress also influenced the content of Na in shoots and roots of two plants, interfering the normal Na homeostasis at the levels of organs and subcellular fractions.