IMBIV   05474
INSTITUTO MULTIDISCIPLINARIO DE BIOLOGIA VEGETAL
Unidad Ejecutora - UE
artículos
Título:
Secretory structures in Flourensia campestris and F. oolepis: ultrastructure, distribution, 2 and (-)-hamanasic acid A secretion.
Autor/es:
SILVA, MARIANA ; TOURN, GRACIELA M; LÓPEZ, DANIELA; GALATI, BEATRIZ G
Revista:
American Journal of Plant Science
Editorial:
Scientific Research Publishing
Referencias:
Año: 2015 vol. 6 p. 925 - 942
Resumen:
In this work, the localization, density, morphology and ultrastructure of secretory structures inaerial organs of Flourensia campestris (FC) and F. oolepis (FO) (Asteraceae) by means of a combinationof light, fluorescence, transmission (TEM) and scanning electron microscopy (SEM) wereexamined. The possible role of secretory structures in the production and secretion of the phytotoxicsesquiterpene (-)-hamanasic acid A ((-)HAA) in both species was also assessed. Capitate glandulartrichomes were found in all reproductive organs of FC and FO, and were being reported forthe first time. These glandular trichomes, typically associated to edges and veins, were of the sametype as those already described for vegetative organs, and were abundant in involucral bracts andcorolla of tubulose and ligulate flowers. Their density in reproductive organs of both species wassimilar (ca. 30/mm2) and lower than that found in leaves (ca. 100/mm2) and stems (ca. 160/mm2in FC, and up to 650/mm2 in FO). Glandular trichomes in vegetative organs followed a species-specific pattern of distribution. TEM and SEM observations suggest that each species differs in theway in which secretory materials are released to the outside: through cracks or pores in FC, orthrough a loose cuticle in FO. Similar inspections of the secretory ducts revealed lipophilic vacuoleslocalized in subepithelial and epithelial cells, in which secretions accumulated before being transferredto the duct. The presence of wall ingrowths in subepithelial cells suggests that granulocrinesecretion operates in these species. Secretory ducts varied in density and diameter among the organsin both species, with the combination being maximal in woody stems. (-)HAA was only detectedin surface secreted resins of both species, and its concentration (2D-TLC, GC-FID) was intimatelyassociated with the distribution and density of glandular trichomes in each organ (capitula, leaves,and stems with primary or secondary growth). In addition, no (-)HAA was detected internally inthe resins collected from secretory ducts. The composition of these resins showed distinctive profilesfor FC and FO, and only four from ca. 30 compounds detected (GC/MS) were shared by bothspecies. In addition to the elucidation of ultrastructural traits, distribution and density of secretorystructures in aerial organs of FC and FO, present findings suggest a functional role for glandulartrichomes in the secretion of the putative phytotoxic allelochemical (-)HAA.