Seed morphometrics and mucilage traits in Helianthemum

This dataset compiles qualitative and quantitative seed traits for species of Helianthemum (Cistaceae) used to investigate the evolution of myxospermy-related seed syndromes across xeric environmental gradients. Seed mucilage chemical composition (pectinic vs. cellulosic) was determined using histochemical staining (methylene blue and ruthenium red), while morphological, structural and hydration-related functional traits were quantified through image analysis and standardized soaking experiments. An integrative Structure–Form–Function framework was applied to characterize multivariate seed phenotypes, from which principal component axes (PCSeed1 and PCSeed2) were derived. Seed syndromes (CES, PHS, PSS) represent emergent phenotypic categories inferred from the combined evidence of chemical composition, functional hydration traits and multivariate phenotypic structure. The dataset provides a comprehensive trait matrix for comparative and evolutionary analyses of seed functional diversification in Mediterranean and xeric plant lineages.