Seed morphology of the tribe Hyoseyameae (Solanaceae)

Seed morphology of 22 species, representing all seven genera of the tribe Hyoscyameae (Anisodus Link, Archihyoscyamus A. M. Lu, Atropanthe Pascher, Hyoscyamus L., Physochlaina G. Don, Przewalskia Maxim. and Scopolia Jacq.) and two putatively related genera in Solanaceae (Atropa L. and Mandragora L.) was investigated using scanning electron microscopy (SEM) in order to evaluate this character for use in systematic analysis. Considerable differences exist in the seed coat morphology both among and within genera in the tribe. The results indicate that the seed coat sculpture of the seeds is irregularly striate-reticulate or cerebelloid in Anisodus and reticulate in all the remaining genera and species. Two types of testal cells can be identified based on their general overall shape and linearity of the anticlinal walls. In one type, the cell shape is isodiametric and varies from polygonal to suborbicular, with the anticlinal wall being nearly straight; in the other type, the cell is irregular in shape, usually not isodiametric, with the anticlinal wall variously sinuate. Fibrils, common in other Solanaceae, are found only in Mandragora. Fine ornamentation of the anticlinal walls of the testal cells varies from smooth to covered with granular, laminar or tuberculate projections. Size and shape of the seeds, and the position of the hilum, appear to be of little systematic significance, but testal cell shape and lateral wall ornamentation are potentially of importance in the taxonomy and phylogeny of the tribe Hyoscyameae. Some of the currently circumscribed genera of the tribe appear not to be monophyletic, but taxonomic decisions must be made with a full suite of morphological, molecular and other data.