The study aimed at characterizing the patterns of natural variation in the tolerance and accumulation capacities for zinc (Zn), cadmium (Cd), and nickel (Ni) between and within edaphic ecotypes of the Zn/Cd/Ni hyperaccumulator, Noccaea caerulescens. Tolerance was assessed in a hydroponic ‘sequential exposure’ test, using the lowest concentration that completely arrested root growth as an end point. Accumulation was measured as the foliar metal concentration after six weeks of growth at 5 µM Zn, 2 µM Cd, or 1 µM Ni. Zn and Cd tolerance were positively correlated, and highest in the calamine ecotype. Ni tolerance was without significant ecotypic variation. The ultramafic ecotype was as Zn-tolerant as the non-metallicolous one, but much more sensitive to Cd. The accumulation capacities for Zn, Cd and Ni were all positively correlated and without significant ecotypic variation. Zn hyperaccumulation capacity was species-wide, but Cd and Ni hyperaccumulation capacities were lacking in four populations (all calamine). There is considerable independent variation among populations regarding their Zn, Cd, and Ni accumulation capacities. This variation is most pronounced within the calamine ecotype, because some populations apparently had adopted an exclusion strategy for Zn or Cd hypertolerance, whereas others had not.

中文翻译：

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Noccaea caerulescens 中锌、镉和镍超耐受性和超积累能力的种内变异

该研究旨在表征锌/镉/镍超富集植物 Noccaea caerulescens 土壤生态型之间和内部对锌 (Zn)、镉 (Cd) 和镍 (Ni) 的耐受性和积累能力的自然变异模式。在水培“连续暴露”测试中评估耐受性，使用完全阻止根生长的最低浓度作为终点。在 5 µM Zn、2 µM Cd 或 1 µM Ni 条件下生长六周后，测量了叶面金属浓度的积累。锌和镉耐受性呈正相关，在炉甘石生态型中最高。Ni耐受性没有显着的生态变异。超镁铁生态型与非金属生态型一样耐锌，但对 Cd 更敏感。锌的积累能力，Cd和Ni均呈正相关，无显着生态变异。Zn 超积累能力是物种范围的，但四个种群（所有炉甘石）缺乏 Cd 和 Ni 超积累能力。不同种群之间的 Zn、Cd 和 Ni 积累能力存在相当大的独立差异。这种变化在炉甘石生态型中最为明显，因为一些种群显然对锌或镉的过度耐受采取了排除策略，而其他种群则没有。