![]() In addition to species-specific metabolic phenotypes, plant species differ in a range of morphological, physiological and phenological functional traits, i.e., traits that affect individual fitness indirectly via their impacts on performance. Common garden studies are a useful approach to compare traits across organisms under standardized conditions, minimizing environmental variation. Ecometabolomics tools are increasingly used to explore such taxon-related differences but also to uncover species-specific responses to certain environmental conditions. Phylogenetic imprints in the metabolome are a result of past and current environmental factors that shape the metabolic composition of plants, leading to species-specific metabolomic niches. When comparing the chemical composition among species, their phylogenetic relatedness should be taken into account, similarly as is done in comprehensive biodiversity studies. These differences across taxa have been, for example, shown for (semi-)polar metabolites in leaves and root exudates. Moreover, taxa differ in their chemodiversity such as the metabolite richness, i.e., the number of metabolites. The genetic repertoire largely determines which metabolic pathways are expressed in a species, with some specialized metabolites occurring in various taxa due to convergent evolution of biosynthetic pathways. The metabolome of a given individual is highly complex and a result of gene by environment interactions. However, whether primary and specialized metabolites correlate in numbers and whether their composition is interlinked in plants has rarely been addressed. Diversification in primary metabolites thus contributes to a high chemodiversity of specialized metabolites, while also other mechanisms reinforced the diversification of the specialized metabolism during evolution. The biosynthetic pathways for primary and specialized metabolites are closely interlinked, as specialized metabolites are synthesized from the primary ones. In contrast, the much more diverse specialized (or secondary) metabolites play major roles in interactions of plants with the abiotic and biotic environment and are specific for certain taxa. Probably less than 10,000 primary metabolites exist, which are found to be more or less ubiquitous in all plants. The primary metabolites, e.g., sugars, organic acids and amino acids, are essential for maintaining cellular homeostasis and are involved in growth, development and reproduction. More than one million metabolites of low molecular weight may occur across all plant species. Plants produce an astonishing diversity of organic molecules in terms of biosynthetic origin, structure and function. Chemodiversity is thereby an important component of biodiversity. ![]() A comprehensive understanding of various leaf traits and their coordination in different plant species may facilitate our understanding of plant functioning in ecosystems. Significant relationships were found between the primary metabolome and nitrogen content and carbon/nitrogen ratio, important traits of the leaf economics spectrum, ranging from acquisitive (mostly deciduous) to conservative (evergreen) leaves. Moreover, metabolomes of deciduous species were distinct from those of evergreens. The leaf metabolomes were highly species-specific but in addition showed some phylogenetic imprints. ![]() Our analyses revealed significant positive correlations between both the numbers and relative composition of primary and specialized metabolites. We investigated these relationships in leaves of 20 woody species from the Mediterranean region grown as saplings in a common garden, using a comparative ecometabolomics approach that included (semi-)polar primary and specialized metabolites. However, relationships between the foliar primary and specialized metabolism in terms of metabolite numbers and composition as well as links with the leaf economics spectrum have rarely been explored. Plants show an extraordinary diversity in chemical composition and are characterized by different functional traits.
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