DyCLE · Dynamics of Cadmium concentrations in Leaves in response to a challenging Environment

Dynamics of Cadmium concentrations in Leaves in response to a challenging Environment

Metal hyperaccumulator plants accumulate extraordinarily high concentrations of metals in their leaves, and very few of these species can be found on both contaminated (metalliferous) and non-contaminated soils. Zinc (Zn) hyperaccumulation (defined as more than 3,000 µg g-1 leaf dry biomass) is a species-wide trait in Arabidopsis halleri (L.) O'Kane & Al-Shehbaz, whereas cadmium (Cd) hyperaccumulation (defined as more than 100 µg g-1 leaf dry biomass) is population-specific. Very little is known about the endogenous and environmental factors determining the exceedingly rare hyperaccumulation of Cd, which in A. halleri is selective for the non-essential Cd(II) in the presence of a large excess of more abundant chemically similar nutrient cations in the soil solution, for example, iron (Fe) and zinc (Zn). Stein et al. (2017) reported Cd hyperaccumulation alongside an unusually large variation in leaf Cd concentrations in two A. halleri populations at Bad Gottleuba (Gott, Germany) and Ukanc (Ukan, Slovenia). The large within-population variation in the extent of Cd hyperaccumulation in the field remains unexplained. Does it reflect a plastic acclimation, and – if so – in response to which environmental factor? Or is it a result of within-population genetic variation? If it reflects an evolutionary adaptation, what selects for it? An understanding of Cd hyperaccumulation and its variability in the field is important, as it will elucidate a novel aspect of ecology and enhance European scientific excellence necessary for the development of more efficient eco-sustainable strategies for the plant-based clean-up of metal-contaminated soils that are not highly contaminated but unsafe for agriculture (phytoremediation). Our aim is to disentangle complex plant-environment interactions and genetic variation in order to understand variation in leaf Cd concentrations in plants and its connection to the elemental defence hypothesis i.e., examine whether plants accumulate higher amounts of Cd in leaves when under herbivory attack. The differential hyperaccumulation of Cd within one and the same population could be (i) environmentally governed by abiotic factors; (ii) a plant response to herbivory; (iii) genetically determined. The three hypotheses are not necessarily mutually exclusive. The objectives of the present project are therefore, (i) address in the field the dynamics of Cd concentrations in leaves and soil over one year in the Gott and Ukan populations; (ii) evaluate the response of different genotypes to herbivory (simulated and insect-mediated) under controlled experimental conditions and in an outdoor garden site; (iii) assess the variation in leaf Cd (and Zn) among different genotypes originating from the same population and between treated and untreated plants; (iv) depending on the results of leaf metal concentration, we also wish to test if glucosinolates (organic compounds acting as a plant defensive compounds against insects) are accumulated in leaves, as well (joint effect hypothesis); (v) investigate the segregation of the Cd hyperaccumulation trait in the progeny of parents contrasting in Cd accumulation.

Data: CORDIS, © European Union