Elemental composition of serpentine plants depends on habitat affinity and organ type

Abstract

AbstractSerpentine soils represent a stressful growing environment for most plants due to a number of edaphic factors, including low concentrations of plant nutrients and high concentrations of heavy metals. Plants in these environments range from weakly resistant to strictly endemic, yet it remains unclear whether serpentine habitat affinity affects plant chemistry, including elemental distribution among various organs. We address this knowledge gap using three confamilial pairs of endemic and non‐endemic plants. First, we determined total and phytoavailable soil concentrations of four nutrients (Ca, Mg, P, K) and three heavy metals (Co, Cr, Ni) across 11 serpentine study sites. Next, we determined the concentrations of these elements in leaves, flowers, and seeds in plants of each species growing on serpentine soil. Soils at the study sites were characteristically high in concentrations of Mg, Ni, Co and Cr, and low in K, P and Ca relative to non‐serpentine soils. Habitat affinity was critical in determining the organ concentrations of Ca, Mg, K, and Co, although concentration often varied by organ type. Relative to non‐endemics, endemics had higher concentrations of Mg and K across all organ types, whereas Ca concentrations were higher for non‐endemics in the leaves but equal for the two reproductive organs. While no difference was observed in Ni or Cr concentrations, endemics contained 56% less Co than non‐endemics across all organ types. These results suggest that serpentine endemics are more effective at acquiring potentially limiting nutrients compared to non‐endemic species, but both endemic and non‐endemic plants exclude most phytotoxic heavy metals. Therefore, growth on serpentine requires common physiological responses of all plants, though high variation in uptake of some key nutrients and exclusion of some metals may reflect differential adaptation to serpentines by non‐endemic and endemic plants.