Comparison of heavy metal contents, fatty acid composition, and palinological characteristics of two different Hypericum species growing in mining-impacted area

Introduction This study comparatively evaluated heavy metal (Al, Cd, Cr, Fe, and Mn) concentrations, fatty acid composition, and palynological characteristics in Hypericum scabrum and Hypericum lydium samples collected from mining-impacted and reference sites of an iron ore operation. Methods Plant samples of H. scabrum and H. lydium were collected from mining-impacted and reference sites in Bingöl Province, Türkiye. Heavy metal concentrations, fatty acid composition, and pollen morphological characteristics were analyzed using ICP-MS, gas chromatography, and light microscopy, respectively. Translocation factor (TF) and statistical analyses were also performed. Results In both species, Al, Cr, Fe, and Mn accumulation was markedly increased in the mining area, whereas the increase in Cd remained relatively limited with statistically significant differences between sites. Translocation factor (TF) analyses revealed higher values for most metals in the mining area; notably, H. lydium exhibited a greater translocation capacity for Fe and Mn. In contrast, TF values for Cr remained below 1 in both species, indicating its retention at the root level. Mining conditions were found to markedly alter the fatty acid composition in both Hypericum species, particularly affecting the balance between saturated and unsaturated fatty acids. Under heavy metal stress, total saturated fatty acids (ΣTSFA; particularly palmitic acid (C16:0) and stearic acid (C18:0)) increased in the mining area, whereas total unsaturated fatty acids (ΣTUSFA; oleic acid (C18:1), linoleic acid (C18:2), and α-linolenic acid (C18:3)) were higher under non-mining conditions. From a palynological perspective, the increased metal load preserved morphological integrity in the pollen of H. scabrum , whereas it caused pronounced changes in the P/E ratio and pollen shape in H. lydium , with statistically significant differences observed. Discussion Overall, the findings suggest that mining-related heavy metal stress influences metal accumulation, fatty acid composition, and pollen characteristics in Hypericum species, although the magnitude and nature of these effects differ between H. scabrum and H. lydium . These species-specific differences indicate that the two species exhibit distinct physiological and morphological responses to heavy metal stress, contributing to a better understanding of plant–heavy metal interactions in mining ecosystems.