Nectary structure, nectar secretion patterns and nectar composition in twoHelleborus species

The morphological and cytological characteristics of nectaries of Helleboru s foetidus and H, bocconei during the secretory period are reported. The ne ctaries are derived from modified petals and secrete nectar continuously fo r about 20 days; they consist of a single layered epidermis, nectar-produci ng parenchyma and photosynthesizing parenchyma. Nectar secretion is holocri ne and the nectar is released by rupture of the wall and cuticle of each ep idermal cell. The nectaries of the two species differ in number and externa l morphology. In H. foetidus, secretion begins before anthesis and secretio n Fate decreases with nectary age. In H. bocconei it begins on the day of a nthesis and proceeds ata constant rate. The nectar has a high sugar content , mainly sucrose, and also contains lipids and proteins.