Palynological analysis of seven Hypericum taxa

The pollen size and exine structure of the following Hypericum L. species were studied by light and scanning electron microscopy: Hypericum dubium, H. x desetangsii, H. hirsutum, H. maculatum, H. montanum, H. perforatum and H. tetrapterum. Of the taxa studied H. maculatum has the smallest pollen grains in average (13.7-20.6 × 11.5-17.2 μm) and H. dubium the largest grains in average (16.0-27.5 × 13.7-22.9 μm). Regular pollen grains of all 7 species are 3-zonocolporate and can be classified as Hypericum perforatum type. For the H. perforatum, H. x desetangsii and H. montanum irregular pollen grains were identified. 6- and 8-pericolpate pollen grains are the most frequent while 12- and 4-syncolporate ones are rare. 3-syncolporate pollen grain is presented as new one among the irregular pollen grains in the genus Hypericum. A weak correlation is found between pollen size and chromosome number. The value of pollen characters for taxonomic purposes and the position of the taxa studied within the genus Hypericum are discussed.