Structure and ultrastructure of leaf and calyx glands in Galphimia brasiliensis (Malpighiaceae)

The present study describes the anatomical structure of calyx and leaf glan ds in Galphimia brasiliensis and analyzes the mechanism of secretion. The g lands are marginal and suprabasal, cup-shaped, sessile, and scarcely visibl e with the naked eye. Light microscopy reveals the following features: a th in, smooth cuticle; unistratified secretory cells; subglandular parenchyma; and vascular bundle supply composed of phloem and xylem with abundant drus es of calcium oxalate. Transmission electron microscopy reveals the presenc e of secretory cells with conspicuous nuclei, dense cytoplasm, lipid drople ts, numerous vesicles, mitochondria, Golgi, rough endoplasmic reticulum (RE R), and elongated plastids with osmiophilic contents. The secretion reaches the apoplastic space and accumulates beneath the cuticle. Finally, the vis cous, translucent exudate is eliminated by mechanical rupture of the cuticl e. Histochemical analysis confirms that lipids are the main constituent. Sm all amounts of polysaccharides were also identified.