Cr/Pb低累积菜心品种筛选及其根际机理研究

以37种菜心(Brassica parachinensis L.)为实验材料,通过土培盆栽试验筛选Cr/Pb相对高累积和相对低累积品种,对筛出品种进行水培和钙离子通道抑制试验,研究相对低累积品种根系活化、吸收重金属的能力。结果表明,特级粗条和油青四九为Cr/Pb相对高累积品种(HC),绿星和极品为Cr/Pb相对低累积品种(LC)。与HC相比,Cr、Pb在LC的根际土溶液中含量较低,且与非根际土溶液之间不存在显著差异(P0.05)。LC的根际土溶解性有机碳(DOC)含量较低,p H较高,导致根际水溶态的Cr、Pb浓度低,说明LC活化重金属能力较弱。钙离子通道抑制剂显著抑制根系对Cr、Pb、Ca的吸收(P0.05),表明菜心根部可能通过钙离子通道途径吸收Cr、Pb,但也不排除同时存在其他铁钾通道途径。低累积品种吸收Ca少,说明其钙离子通道不活跃,导致由此进入菜心体内的Cr、Pb也少。根到可食部分的转运作用对菜心低累积Cr、Pb影响不显著(P0.05)。因此,LC根际分泌DOC和H+较少,钙离子通道不活跃,两者可能导致LC对根际土壤Cr、Pb的活化、吸收能力较弱,进而减少其可食部分对Cr、Pb累积。

Screening and preliminary rhizosphere mechanisms of low Cr/Pb accumulation cultivars of Chinese flowering cabbages (Brassica parachinensis L.)

A pot experiment was carried out to select relatively high Cr/Pb accumulating cultivars (HC) and relatively low Cr/Pb accumulating cultivars (LC) from 37 cultivars of Chinese Flowering Cabbages (Brassica parachinensis L.). A hydroponic experiment and an experiment by Ca ion channel blocker were performed on the selected HC and LC cultivarto investigate the mechanism of Cr/Pb uptake and mobilization by roots of LC cultivars. Two HC cultivars (Tejichutiao and Youqingsijiu) and two LC cultivars (Lvxing and Jiping) were selected out. Cr and Pb concentrations in rhizosphere soil solution of LC cultivars are significantly lower than those of HC cultivar, but were not significantly differ ent to those of bulk soil solution. Meanwhile, the concentrations of dissolved organic carbon (DOC) in the rhizosphere of LC cultivars were ob viously lower than that of HC cultivars. The pH values in the rhizosphere of LC cultivars were also higher than those of HC cultivars. These results indicated a lower mobilization of Cd/Pb in the rhizophsere of LC cultivars. Ca ion channel blocker significantly inhibited Cr, Pb and Ca uptake by roots (P<0.05), which suggested that Cr and Pb might be absorbed by cabbage roots via Ca ion channel, although these metals might also be absorbed through Fe and/or K pathway. The less Ca uptake possibly meant inactive Ca ion channel in roots of LC cultivar, resulting less Cr and Pb uptake through Ca pathway. The translocation of Cr and Pb from roots to edible parts of cabbage has no significant (P<0.05) effect on Cr and Pb accumulation in edible parts of cabbage. In conclusion, less DOC and H⁺ secreted by roots, and inactive Ca ion channels may result in lower Cr and Pb uptake and accumulation in Chinese flowering cabbages.