5 - The seeds of Gentianaceae

Summary

ABSTRACT

Seeds of representatives of 78 genera of the Gentianaceae were studied using scanning electron microscopy. Seeds of most taxa are relatively small, often between 0.3 mm and 0.7 mm in length. They develop from unitegmic, tenuinucellate ovules and are exotestal or sometimes have collapsed or reduced testas. In spite of their small size, the seeds show an extensive diversity in micromorphology.

Seed structure is often characteristic at the tribal, subtribal, or generic level. Testa cells vary in orientation, shape, undulation of the anticlinal walls and pitting of the inner walls. The outer wall is always thin and without a cuticular structure. Except for the inclusion of the Potaliinae, and the delimitation of the Saccifolieae, seed structure sustains the new classification of the Gentianaceae as proposed by Struwe et al. in Chapter 2 of this volume. Crystallized structures were found upon and under the exotestal cuticle of several genera of the Chironieae, Coutoubeinae, and Faroinae.

Seeds of the mycotrophic/saprophytic genera are all small and may be strongly reduced. Owing to adaptations to a saprophytic lifestyle, seed characters of saprophytes are of limited taxonomic use at the subgeneric level.

The seeds of the majority of species are dispersed by the wind. Most species are wind ballists. Endozoochorous dispersal is known in Potaliinae and in one species of Chironia. Seeds may belong to different seed bank types. Seed germination is epigeal. Seedlings are small and phanerocotylar.

Keywords: dispersal, embryology, Gentianaceae, germination, seed morphology, testa.