不同积累型苋菜(Amaranthus mangostanus L.)镉吸收转运特征差异性研究

【目的】比较高积累型苋菜品种Tianxingmi与低积累型苋菜品种Zibeixian在Cd胁迫下Cd吸收转运特征差异性，揭示苋菜品种Tianxingmi高积累镉的机理。【方法】采用水培试验，添加代谢抑制剂来研究两品种苋菜根系吸收Cd的主要途径。分别在30 μmol/L CdCl₂处理4 h、8 h、16 h、1 d和2 d采样测定，采用非损伤微测技术（Non-invasive micro-test technique，NMT），进行植物活体动态测试，调查、测量两品种苋菜根系Cd2+离子流特征，比较了两品种对代谢抑制剂的反应。【结果】在30 μmol/L CdCl₂处理1 d后，Tianxingmi生物量达到最大值5.90 g/plant，是Zibeixian生物量的二倍；Tianxingmi根、茎和叶中Cd浓度分别为609、254和62.3 mg/kg，分别是Zibeixian的1.4倍、1.9倍和1.6倍，地上部和全株的Cd累积量分别高达602.0、1308 μg/plant；Tianxingmi富集系数（BCF）与转运系数（TF）分别为Zibeixian的2.1倍和1.5倍，这些结果两品种均表现出显著性差异（P < 0.05）。NMT技术测定两品种根系Cd2+离子流，通过扫描位点测定发现，距根尖0~300 μm范围内两品种苋菜根系Cd2+内流最强且差别最大，并在此做定点位点测定，发现Tianxingmi根系Cd2+内流是Zibeixian根系Cd2+内流的3.75倍，说明了两品种的富集特征与NMT结果一致。添加代谢抑制剂处理显著降低了高积累型Tianxingmi各器官中的Cd浓度，富集系数（BCF）与转运系数（TF），以及根系Cd2+内流（P < 0.05），主动吸收特征明显，而对低积累型Zibeixian的相关生理指标影响不大。【结论】两苋菜品种Cd吸收转运特征均表现出显著性差异。Tianxingmi具有更强的Cd吸收和向地上部转运与累积能力，并且根系对Cd的吸收与转运是主动需能的过程，共质体途径在Cd进入Tianxingmi根系并向地上部运输的过程中起着主要作用。

Characteristics of Cd uptake and translocation in two cultivars of Amaranth (Amaranthus mangostanus L.)

Objectives] Characteristics of absorption and translocation of Cd in amaranth (Amaranthus mangostanus L.) with different Cd accumulation abilities were compared under cadmium (Cd) stress.Methods]Hydroponic experiments basing Hoagland nutrient solution were conducted with two amaranth cultivars, Zibeixian (ZBX, a low Cd accumulator) and Tianxingmi (TXM, a high Cd accumulator) as testing materials. Plant samples were collected after the exposure to Cd stress solution (30 μmol/L CdCl2) of 4 h, 8 h, 16 h, 1 d and 2 d. The Cd contents were determined using ICP-OES method, and the dynamic accumulation in roots was monitored using none-invasive micro-test technique (NMT). The responses of the two cultivars to metabolic inhibitor were also compared.Results]After 1 d exposure, the total dry biomass of TXM is twice of ZBX, and reached to the maximum value of 5.90 g/plant. The cadmium contents in the roots, stems and leaves of TXM reached 609, 254 and 62.3 mg/kg, which were 1.4, 1.9 and 1.6 times of those of ZBX. The Cd accumulation amounts in the shoots and whole plants of TXM reached 602.0 and 1308 μg/plant. The bioaccumulation factor and translocation factor of TXM were 2.1 and 1.5 times of those of ZBX. All these results were significant difference between the two cultivars of amaranth (P < 0.05). The biggest net Cd2+ influx difference in the screening test of roots was within 0–300 μm from the tips. The net Cd2+ influx in roots of TXM was 3.75 times of that of ZBX, and the enrichment characteristic was consistent with the result of NMT. Metabolic inhibitor significantly reduced the Cd indexes of TXM (P < 0.05), but had little effect on Zibeixian.Conclusions]Compared with the cultivar ZBX, the cultivar TXM has stronger ability of Cd uptake and root-to-shoot translocation capacity, which is an active process, and has the symplastic pathway rather than the apoplastic bypass.