ULTRASTRUCTURE AND FUNCTION OF FLORAL NECTARIES OF CHAMELAUCIUM-UNCINATUM (MYRTACEAE)

Nectar is secreted for up to 11 d after anthesis in Chamelaucium uncin atum. The volume and sucrose concentration secreted varies between Bow ers, plants and days. The period of nectar secretion coincides with th e period of pollen presentation and stigmatic receptivity suggesting n ectar is part of an efficient reproductive strategy in C. uncinatum. T he nectary of C. uncinatum consists of the entire upper surface of the ovary and hypanthium. The epidermis of the nectary is covered by a th ickened cuticle which is only broken at the sites of the numerous modi fied stomata which are scattered across its surface. It is suggested t hat nectar is secreted onto the surface of the ovary via these modifie d stomata. The presence of extensive and well developed endoplasmic re ticulum, mitochondria and Golgi bodies in the nectar secreting cells i ndicates that a granulocrine mechanism of secretion is occurring in C. uncinatum. (C) 1996 Annals of Botany Company