RESUMEN
Plant structures that secrete lipids and phenolic compounds are often associated with the protection and development of organs against desiccation, in addition to the protection they provide against animals, as the capitate trichomes of Adenocalymma magnificum. Understanding the glandular activities that occur in these trichomes has required the study of their ontogeny, structure, ultrastructure and histochemical aspects; the interpretation of their ecological functions or evolutionary history is complicated by the scarcity of reports on calicinal trichomes that are not nectar-secreting. Samples of floral calyx in anthesis and flower buds at different stages of development were fixed and processed according to the methods for light and electron microscopy. The trichomes are randomly distributed throughout the entire inner surface of the calyx and are also visible on the flower buds. These capitate glandular trichomes were composed of a peduncle, having up to nine cells, and a multicellular secretory head with their cells in columnar format and arranged in disc form. The collar cell, which is under the secretory head, divides anticlinally and arranges itself side by side with the mother cell. As they develop, they bend with some of them becoming adpressed to the calyx. Histochemical tests indicate that the secretory head cells produce lipid substances, acidic lipids and phenolic compounds. In the secretory head, the vacuome is dispersed and the cytoplasm possesses a great number of smooth endoplasmic reticulum and leucoplasts, organelles involved in the production of osmiophilic substances. In some regions of the secretory cells, cuticle detachment was observed; however, the accumulation of secretions was not observed. This study describes, for the first time, the origin, development, and secretion process of the calicinal trichomes of Adenocalymma magnificum, showing that production of lipophilic substances is important for this plant, possibly the trichomes may be involved in the plants chemical defense against insects, offering protection against herbivores. Rev. Biol. Trop. 63 (2): 537-544. Epub 2015 June 01.
Las estructuras que secretan lípidos y compuestos fenólicos estan frecuentemente asociadas a la protección y desarrollo de órganos que protegen contra la desecación, además de la protección que estas proporcionan contra el ataque de animales. Los tricomas capitados de Adenocalymma magnificum son estructuras de este tipo. Para comprender las actividades glandulares que ocurren en estos tricomas es necesario estudiar su ontogenia, estructura, ultraestructura y aspectos histoquímicos. La interpretación de sus funciones ecológicas o historia evolutiva es compleja, y pocos son los estudios que se enfocan en los tricomas calicinales no secretores de néctar. Las muestras del cáliz floral en antesis y botones florales en diferentes estadios de desarrollo fueron fijadas y procesadas de acuerdo con los métodos para microscopia de luz y electrónicos. Los tricomas de A. magnificum están aleatoriamente distribuidos en toda la extensión de la superficie interna del cáliz, también observados en los botones florales. Estos tricomas son glandulares capitados, compuestos de un pedúnculo largo que posee hasta nueve células y una cabeza secretora multicelular, con células en columnares dispuestas en disco. La célula del collar, que esta sobre las células de la cabeza secretora, se divide anticlinalmente organizándose lado a lado con las células madre. Con el crecimiento de los tricomas, estos mismos se curvan y algunos quedan adpresos al cáliz. Las pruebas histoquímicas indicaron que las células de la cabeza secretora producen sustancias lipídicas, lípidos ácidos y compuestos fenólicos. En la cabeza secretora la vacuoma esta dispersa y posee abundante retículo endoplasmático liso y leucoplastos, los cuales son organelos involucrados en el proceso de producción de sustancias osmiofílicas. En algunas regiones de las células secretoras la distensión de la cutícula fue observada, sin embargo, no fue verificada la acumulación de secreción. Este trabajo describe por primera vez el origen, desarrollo y proceso de secreción de tricomas calicinales de A. magnificum, mostrando que la producción de substancias lipofílicas es importante para esta especie, ofreciendo posiblemente protección contra la herbivoría.
Asunto(s)
Bignoniaceae/anatomía & histología , Compuestos Fenólicos/análisis , Tricomas/clasificaciónRESUMEN
Xanthanolides, as the sesquiterpene lactones, are reportedly the major components for the pharmacological properties of X. strumarium L. species. Phytochemical studies indicated that the glandular structures on the surface of plant tissues would form the primary sites for the accumulation of this class of the compounds. As the interface between plants and their natural enemies, glandular trichomes may vary with respect to which of their chemicals are sequestered against different herbivores in different ecologies. However, to date, no data are available on the chemical characterisation of X. strumarium glandular cells. In this study, the trichome secretions of the X. strumarium species originating from nineteen unique areas across eleven provinces in China, were analysed by HPLC, LC-ESI-MS and NMR. For the first time three distinct chemotypes of X. strumarium glandular trichomes were discovered along with the qualitative and quantitative evaluations of their presence of xanthanolides; these were designated glandular cell Types I, II, and III, respectively. The main xanthanolides in Type I cells were 8-epi-xanthatin and xanthumin while no xanthatin was detected. Xanthatin, 8-epi-xanthatin, and xanthumin dominated in Type II cells with comparable levels of each being present. For Type III cells, significantly higher concentrations of 8-epi-xanthatin or xanthinosin (relative to xanthatin) were detected with xanthinosin only being observed in this type. Further research will focus on understanding the ecological and molecular mechanism causing these chemotype differences in X. strumarium glandular structures.