Development, structure and function of bracteal nectaries in Caamembeca laureola (A.St.Hil & Moq.) JFB Pastore (Polygalaceae)

Abstract

We conducted anatomical studies on glands of the Polygalaceae aiming at characterizing the morphology and function of the inflorescence glands of Caamembeca laureola (A.St.Hil & Moq.) JFB Pastore. Glucose was detected using Glicofita Plus Ò , and insect visitors were observed along the entire reproductive axis. Standard techniques on plant anatomy were used for observation under light and scanning electron microscopies. Gland exudation starts at anthesis, and the secretory activity continues up to the fruiting stage. The presence of glucose in the glands allows for their identification as extrafloral nectaries. The secretory tissue in the gland occupies the medullar region and is surrounded by phloem. Xylem is observed only at nectary base. The vascular bundle supplying this structure is the same one that supplies the flower bract, located at the side opposite the nectary. Our study thus lays groundwork for the investigation on the morphology of the glands found on the reproductive axis in the Polygalaceae. These glands are named as bracteal nectaries, the first such report for the entire family. This thus brings up new data and interpretations regarding the role that such structures play in the studied group and also attributes diagnostic value to the character.