Seed morphology of Hypericum (Hypericaceae) in China and its taxonomic significance

The seed morphology of 40 taxa within the genus Hypericum (Hypericaceae) from China, representing 9 sections of the genus, was examined using both Light and Scanning Electron Microscopy to evaluate the taxonomic relevance of macro- and micro-morphological features. Details articulating variation in seed size, color, shape, appendages, and seed coat ornamentation are described, illustrated, and compared, and their taxonomic importance is discussed. Seeds were generally brown in color and cylindric-ellipsoid to prolonged cylindric in shape. Seed size displayed wide variation, ranging from 0.37-1.91 mm in length and 0.12-0.75 mm in width. Seed appendages were observed as a characteristic morphological feature. Seed surface ornamentation has high phenotypic plasticity, and four types (reticulate, foveolate, papillose, and ribbed) can be recognized. In general, seed color and shape have limited taxonomic significance. However, some other features represent informative characters that can be used efficiently in distinguishing the studied taxa at the section and/or species levels. The findings illustrate that considerable taxonomic knowledge can be obtained by investigating the seed features of Hypericum, and the use of Scanning Electron Microscopy can reveal inconspicuous morphological affinities among species and play a role in taxonomic and systematic studies of the genus Hypericum.

Automated summary

The seed morphology of 40 taxa within the genus Hypericum (Hypericaceae) from China was studied using Light and Scanning Electron Microscopy to assess the taxonomic significance of macro- and micro-morphological features. Seed size, color, shape, appendages, and seed coat ornamentation were described, illustrated, and compared. While seed color and shape had limited taxonomic importance, other features were informative in distinguishing taxa at the section and/or species levels. Scanning Electron Microscopy was found to be useful in revealing inconspicuous morphological affinities among species and played a role in taxonomic and systematic studies of Hypericum.