Floral nectaries in Sapindaceae s.s.: morphological and structural diversity, and their systematic implications

SOLIS, STELLA MARIS; ZINI, LUCÍA M.; GONZÁLEZ, VALERIA V.; FERRUCCI, MARÍA S.

PROTOPLASMA

SPRINGER WIEN

Lugar: Viena; Año: 2017

0033-183X

We investigated the morphology and structure of the floral nectary in 11 Neotropicalgenera belonging to the subfamilies Dodonaeoideae and Paullinioideae (Sapindaceae)from southern South America representing three tribes (Dodonaeaeae, Paullinieae and Melicocceae), in relation to other floral traits in species with contrasting morphologicalflower characteristics. Nectary organization was analyzed under light, stereoscopic andscanning electron microscopes; Diplokeleba floribunda N.E. Br. was also observedusing transmission electron microscopy. Our comparative data may contribute to theunderstanding of floral nectary evolution and systematic value in this family. Thenectaries were studied in both staminate and pistillate flowers. All the floral nectariesare typical of Sapindaceae: extrastaminal, receptacular, structured, and persistent. Theanatomical analysis revealed a differentiated secretory parenchyma and an inner nonsecretoryparenchyma; the nectary is supplied by phloem traces and, less frequently,by phloem and xylem traces. Nectar is secreted through nectarostomata of anomocytictype. The anatomical analysis showed the absence of nectary in the three morphs of D.viscosa flowers. Nectary ultrastructure is described in D. floribunda. In this species thechange in nectary color is related to progressive accumulation of anthocyanins duringthe functional phase. We found relatively small variation in the nectary structuralcharacteristics compared with large variation in nectary morphology. The latter aspectagreed with the main infrafamilial groupings revealed by recent phylogenetic studies,so it is of current valuable systematic importance for Sapindaceae. In representativesof Paullinieae, the reduction of the floral nectary to 4-2 posterior lobes should beinterpreted as a derived character state.