The Elemental Composition of Land Plants: A Global Database and Meta-analysis.

Although plants likely take up all elements present in the soil environment, the elemental composition of land plants remains poorly characterized beyond essential nutrients. A comprehensive global database of plant tissue concentrations spanning 52 elements was compiled from 5,474 samples across 73 countries, 21 climate classes, and 26 soil groups. Robust global means for macronutrients, micronutrients, transition and heavy metals, metalloids, and rare earth elements are reported using mixed-effects models that account for study level variation. Global concentrations are also reported for roots and shoots, domesticated and wild plants, edible and nonedible plants, N-fixation symbiosis, and for various plant types including trees, shrubs, vines, forbs, sedges, grasses, ferns, and mosses. Many nonessential elements (i.e. transition metals, rare earth elements) exist in plant tissues in higher concentrations than micronutrients, with 20 elements higher than Mo. Phylogenetic analyses across major plant lineages revealed strong evolutionary constraints on elemental composition, with Ornstein-Uhlenbeck models indicating stabilizing selection toward lineage-specific optima for most elements. The plant elements most likely to predict taxonomic grouping through unsupervised machine learning (XGBoost) followed S > Ca > N > Zn > Ba > Cu > Pb > Sb > Cd > P. Multivariate ordinations separated domesticated crops from wild species, driven primarily by macronutrient enrichment in crops. Further, key atomic ratios differed between domesticated and wild plants, driven by differences in Zn:Cd, K:Na, N:S, and N:P. Systematic hyperaccumulator identification revealed 53 species across diverse taxa, with high Ni, Cu, and Pb uptake as the most prevalent indicator of hyperaccumulation. The study provides reliable and comprehensive estimates of the elemental composition of land plants and highlights that lesser studied elements constitute a considerable fraction of plant tissues.