Department of Biomedical Experimental and Clinical Sciences, University of Firenze, Viale Morgagni 50, 50134, Firenze, Italy.
Department of Biology, University of Firenze, Via G. La Pira 4, 50121, Firenze, Italy.
Planta. 2020 Nov 10;252(6):99. doi: 10.1007/s00425-020-03507-x.
Odontarrhena is a highly diverse genus of Ni-hyperaccumulators. Here, we demonstrate substantial inability to accumulate Ni in the facultative serpentinophyte O. sibirica, which seems a unique case among the numerous species of the genus that grow on ultramafic soils. Odontarrhena is the most diverse genus of Ni-accumulating plants in W Eurasia, with most taxa growing obligatorily or facultatively on ultramafic soils. A notable exception may be O. sibirica, a facultative serpentinophyte from the E Mediterranean and W Asia in which accumulation ability is still enigmatic. We addressed this issue using observational and experimental methods. Atomic Absorption Analysis of 33 herbarium specimens and plant and soil samples from seven ultramafic and non-ultramafic sites in Greece revealed shoot Ni values always much lower than 1000 µg g, non-significant differences between plants from the two soil types and no relationship with soil pH. Only two Turkish specimens from waste mines had shoot Ni concentration > 1000 µg g. The reasons for this deviating result remain obscure, but may be associated with inherent peculiarities of the local populations. When cultivated together with congeneric Ni-accumulating species on the same natural ultramafic soil, only O. sibirica was unable to accumulate the metal. Although plant growth was stimulated in hydroponics at relatively low NiSO levels (50-150 µM), as typical for hyperaccumulators, Ni-accumulation occurred only at higher concentrations which had a toxic effect. This peculiar combination of Ni-response traits could be the result of a partial evolutionary loss of ability with respect to all other Ni-accumulating congeneric species. For this, O. sibirica could represent a unique model system for further studies on the evolutionary dynamics, physiological mechanisms and genetic control of metal accumulation and homeostasis.
齿缘草属是高度多样化的镍超积累植物属。在这里，我们证明了兼性蛇纹岩植物西伯利亚齿缘草在积累镍方面的显著能力缺失，这在生长在超基性土壤上的众多属种中似乎是一个独特的案例。齿缘草属是欧亚大陆最具多样性的镍积累植物属，大多数种属都必须或兼性地生长在超基性土壤上。一个显著的例外可能是西伯利亚齿缘草，它是一种来自东地中海和西亚的兼性蛇纹岩植物，其积累能力仍然是个谜。我们使用观察和实验方法来解决这个问题。对 33 个标本和来自希腊 7 个超基性和非超基性地点的植物和土壤样本进行原子吸收分析，结果表明，茎部的镍含量始终远低于 1000µg/g，两种土壤类型的植物之间没有显著差异，与土壤 pH 也没有关系。只有来自土耳其两个废弃矿山的两个标本的茎部镍浓度>1000µg/g。造成这种偏离结果的原因尚不清楚，但可能与当地种群的固有特性有关。当与同一种天然超基性土壤上的同属镍积累种一起栽培时，只有西伯利亚齿缘草无法积累金属。尽管在相对较低的 NiSO 水平（50-150µM）下的水培中，植物生长得到了刺激，这是超积累者的典型特征，但只有在更高的浓度下才会发生镍积累，而高浓度的镍会产生毒性。这种特殊的镍响应特征组合可能是相对于所有其他镍积累的同属种属而言，能力部分进化丧失的结果。对于西伯利亚齿缘草来说，它可能代表了一个独特的模型系统，可用于进一步研究金属积累和稳态的进化动态、生理机制和遗传控制。
