Habitat-specific allocations of elements in Atriplex lentiformis seeds hint at adaptation to metal toxicity

Abstract

Self-sustaining vegetation in metal-contaminated areas is essential for rebuilding the ecological resilience and community stability in degraded lands. Metal-tolerant plants originating from contaminated post-mining areas may hold the key to successful plant establishment and growth. Yet, little is known about the impact of metal toxicity on reproductive strategies, metal accumulation and allocation patterns at the seed stage. Our research focused on metal tolerant Atriplex lentiformis, examining the effects of toxic metal(loid) concentration in soils on variability in its reproductive strategies, including germination patterns, elemental uptake, and allocation within the seeds. We employed advanced imaging techniques like synchrotron X-ray Fluorescence Microscopy (XFM; 2D scans and 3D tomograms) combined with ICP-MS to reveal significant differences in metal(loid) concentration and distribution within the seed structures of A. lentiformis from contrasting habitats. Exclusive Zn hotspots of high concentrations were found in the seeds of the metallicolous accession, primarily in the sensitive tissues of shoot apical meristems and root zones of the seed embryos. The findings of this study offer novel insights into phenotypic variability, metal tolerance and accumulation in plants from extreme environments. This knowledge can be applied to enhance plant survival and performance in land restoration efforts.

Keywords: Germination; heavy metals; imaging; metal adaptation; metallophyte; mine tailings; phytoremediation; seed; synchrotron X-ray fluorescence microscopy (XFM); zinc.