Secretory Structures in Flourensia campestris and F. oolepis: Ultrastructure, Distribution, and (-)-Hamanasic Acid A Secretion

In this work, the localization, density, morphology and ultrastructure of secretory structures in aerial organs of Flourensia campestris (FC) and F. oolepis (FO) (Asteraceae) by means of a combination of light, fluorescence, transmission (TEM) and scanning electron microscopy (SEM) were examined. The possible role of secretory structures in the production and secretion of the phytotoxic sesquiterpene (-)-hamanasic acid A ((-)HAA) in both species was also assessed. Capitate glandular trichomes were found in all reproductive organs of FC and FO, and were being reported for the first time. These glandular trichomes, typically associated to edges and veins, were of the same type as those already described for vegetative organs, and were abundant in involucral bracts and corolla of tubulose and ligulate flowers. Their density in reproductive organs of both species was similar (ca. 30/mm2) and lower than that found in leaves (ca. 100/mm2) and stems (ca. 160/mm2 in FC, and up to 650/mm2 in FO). Glandular trichomes in vegetative organs followed a speciesCorresponding authors.