Septal nectaries

Massive septal nectaries may have predisposed Bromeliaceae to exceptional dependence on vertebrates rather than less demanding insect pollinators. Organ structure conforms to the "labyrinthine common nectarial cavity type (Schmidt 1985), but details vary with other aspects of the ovary (e.g., Cecchi Fiordi and Palandri 1982; Böhme 1988; Chapter 12). Varadarajan and Brown (1988) examined numerous Pitcairnioideae chosen to represent a range of oral morphologies and pollination syndromes. They reported that three longitudinal systems of channels, one per septum, always join within the ovary axis (Fig. 3.1A). From there, nectar exits through circular or slit-like ori ces at locations in uenced by the hypogenous or epigenous condition of the ower. Triradiate cavities sometimes extend upward to the style along circuitous routes.

Glandular tissue occupies different portions of the epithelium lining the collecting system. Superior-ovaried taxa (e.g., Deuterocohnia schreiten, Dyckia ragonesei) possess three additional secondary nectar channels oriented toward the placenta, while half and fully inferior-ovaried gynoecia (e.g., Pitcairnia heterophylla, Puya harmsii) develop septal channels only. Simple sugars dominate the relatively dilute secretions (Table 6.3).

Böhme (1988) examined over 90 species representing all three subfamilies in her attempt to identify features of potential systematic signi cance. Gynoecial position and the manner in which the three carpels join proved less consistent than the literature claims. She also reported that the amount of nectariferous tissue varied, as did its con guration and that of the collection system. Auxiliary secretory tissue sometimes extended beyond the gynoecium, occasionally on to the petal bases. Böhme constructed a scheme to depict nectary evolution, and attempted to reconcile gland structure with oral biology.

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