TRICHOMES ON VEGETATIVE AND REPRODUCTIVE-ORGANS OF LEONOTIS-LEONURUS (LAMIACEAE)

The types of glandular trichomes, their ontogeny and pattern of distribution on the vegetative and reproductive organs of Leonotis leonurus at different stages of development, are studied by light and scanning electron microscopy. Two morphologically distinct types of glandular trichomes (peltate and capitate) are described. Peltate trichomes, at the time of secretion, are characterized by a short stalk, which is connected with a large spherical head composed of eight cells in a single layer. Capitate trichomes can be divided into various types. Generally, they consist of a four-celled head supported by one or three stalk cells. The two kinds of trichomes differ in the secretion process. In the peltate trichomes, the secretory product seems to remain accumulated in a subcuticular space, unless an external factor damages it. In the capitate trichomes, this product probably becomes released through micropores. On the leaves peltate and capitate trichomes are abundant, while on the flowers only the peltate trichomes are numerous and the capitate are rare or absent. (C) 1995 Annals of Botany Company