Species adaptation in serpentine soils in Lesbos Island (Greece): metal hyperaccumulation and tolerance

Abstract

Serpentine (ultramafic) soils, containing relatively high nickel and other metal concentrations, present a stressful environment for plant growth but also a preferred substrate for some plants which accumulate nickel in their tissues. In the present study we focused on: (1) the relationships between serpentine soils of Lesbos Island (Greece) and serpentinophilic species in order to test their adaptation to the 'serpentine syndrome', and (2) the Ni-hyperaccumulation capacity of Alyssum lesbiacum, a serpentine endemic, Nihyperaccumulating species, recorded over all its distribution for the first time. We sampled soil and the most abundant plant species from the four serpentine localities of Lesbos Island. Soil and leaf elemental concentrations were measured across all the sites. Our results confirmed our hypothesis that serpentinophilic species are adapted to elevated heavy metal soil concentrations but restricting heavy metal concentration in their leaves. We demonstrated that different A. lesbiacum populations from Lesbos Island present differences in Ni hyperaccumulation according to soil Ni availability. Our results highlighted the understanding of serpentine ecosystems through an extensive field study in an unexplored area. Alyssum lesbiacum and Thlaspi ochroleucum emerge as two strong Ni hyperaccumulators with the former having a high potential for phytoextraction purposes.

Trace Metals in Soils and Several Brassicaceae Plant Species from Serpentine Sites of Serbia

“…The content of the available Fe varied from 0.13 g kg -1 to 0.67 g kg -1 and it was high in the loamy and alkaline soils [24]. Concentrations of the total and available trace elements (Ni, Zn, Mn, Cu) in the soils are presented in [6,25,30,37,43]. Concentrations of available Ni and Mn in all soils were much higher than those presented for ultramafi c soils from Iran [17,18].…”

“…In roots and shoots of A. montanum, A. repens, E. linariifolium and R. lippizensis (shoots only) the Ca/Mg ratio > 1 (1.12-6.06) was noticed. High Ca contents in roots and shoots of these three species are the consequence of the unusual ability of these plants to accumulate high Ca concentrations in their tissues, even from the soils with low [25,27,43]. Therefore, some of the serpentine plants must possess a mechanism to limit uptake of Mg and/or a high absorption capacity for selective Ca uptake [31].…”

“…Although Mn content in soil samples was relatively high, its concentration in plant tissues was several times lower; in roots Mn content was in the range from 7.6 mg kg -1 (A. repens at SP7) to 96.6 mg kg -1 (C. plumieri at SP9) and in shoots it varied from 13.2 mg kg -1 (A. repens at SP7) to 120 mg kg -1 (C. plumieri at SP8). It is assumed that species growing in serpentine soils can restrict transport of Mn to the shoots and maintain a relatively low concentration of metals in aboveground parts even at high concentrations in soils [25]. Mn concentrations in plants lower than those in corresponding soils can be attributed to soil pH (mean value 7), since at this pH value Mn forms insoluble oxides resulting in reduced availability [2].…”

Stability of the Inherent Target Metallome in Seed Crops and a Mushroom Grown on Soils of Extreme Mineral Spans

“…Comparable long-term adaptations are strongly suggested by the seed's Ni content of up to 4800 mg kg´1 from the Ni hyperaccumulator Alyssum lesbiacum endemic to serpentine soils [75]. Moreover, the inherent degree of Ni hyperaccumulation in different A. lesbiacum accessions varied with the Ni content of their local soils [76] indicating that the regional within-species variations as studied for the shoot Zn of plants are actually in part an evolutionary trait [77].…”

“…Comparable long-term adaptations are strongly suggested by the seed's Ni content of up to 4800 mg kg −1 from the Ni hyperaccumulator Alyssum lesbiacum endemic to serpentine soils [75]. Moreover, the inherent degree of Ni hyperaccumulation in different A. lesbiacum accessions varied with the Ni content of their local soils [76] indicating that the regional within-species variations as studied for the shoot Zn of plants are actually in part an evolutionary trait [77]. It is then not surprising that mineral concentrations needed by herbivores (Table 4) [10,13] have also been adapted to the order of those considered normal by plants [7,68] and adequate for seed germination in the given geochemical environment [27,78].…”