Morphology and Anatomy of Resin Glands in Salix Lucida (Salicaceae)

Resin glands on the first leaves to emerge occur at the tip of each marginal dentation of the lamina and stipule, and on the adaxial surface of the stipule and lamina bases (the latter often extend onto the petiole). Successive emerging leaves show increases in number of basilaminar glands, because increasingly elaborate multiglandular stalks develop. Glands in all locations are conical or domed, with a palisade‐like epidermis subtended by 5–6 layers of parenchyma which contains druse crystals. A single vascular bundle (sometimes two or three) ends in a small knob of tracheary elements. Glands usually secrete liquid resin that covers the gland and surrounding area and under certain conditions, particularly in low humidity, resin is extruded as a filament from a pore in the gland apex, a mode of resin secretion not described previously. Glands secreting liquid resin have an apical dimple, but presence of a pore has not been established.