A scanning electron microscopy study of Taxus leaves as related to taxonomy.

Scanning electron microscopy, when applied to the surfaces of the needles of Taxus spp. (yew) revealed features that appear useful in the taxonomy of this tree species which yields the important anticancer drug, taxol. For instance, all of the four North American species have 3-5 rows of stomata on one-half of the abaxial leaf surface, whereas all of the others, including those from Europe and Asia, have 7-10 rows of stomata. The appearance of individual or fused papilliform epidermal cells and their arrangement on the leaf surface also is a feature that varies between species. Patterns of wax formation appeared on all species of yew examined but none could characteristically be assigned to a given species. Wax pattern variation was dependent upon age, environment, and probably to some extent, species differences. This study may provide some additional useful and reliable indicators in Taxus taxonomy.