Morfo-anatomía foliar de Araujia odorata (Apocynaceae-Asclepiadoideae) en un gradiente altitudinal: histoquímica de laticíferos / Foliar morpho-anatomy of Araujia odorata (Apocynaceae-Asclepiadoideae) in an altitudinal gradient: histochemistry of laticifers

Araujia odorata is a sub-shrub native from Argentina, Brazil, Paraguay and Uruguay, whose latex, roots and leaves are used in traditional medicine. The objective of this work is to study the foliar morpho-anatomy of six populations in an altitudinal gradient (359-2155 m.a.s.l.) of Northwestern Argentine and to determine the nature of the compounds present in the laticiferous of the stems and fruits using conventional techniques for plant anatomy. The populations under study did not show significant morpho-anatomical differences. They presented simple leaves, pinnated brochydodromous venation, amphiestomatic isolateral lamina, brachy, anomo and amphicyclocytic stomata, eglandular trichomes, midvein with bicolateral vascular bundle and non-articulated laticifers continuous in the petiole, stem and fruits. Differences in the quantified foliar parameters are observed, however, only the density of trichomes, stomata and the thickness of the cuticle are positively correlated with the altitudinal gradient, indicating phenotypic plasticity. Histochemical analysis of laticifers and other stem idioblasts of A. odoratawas performed for the first time.

Araujia odorata, es un subarbusto nativo de Argentina, Brasil, Paraguay y Uruguay, cuyo látex, raíces y hojas son utilizados en medicina popular. Se plantea como objetivo realizar un estudio morfo-anatómico foliar de seis poblaciones del Noroeste Argentino en un gradiente altitudinal (359-2155 m.s.n.m) y determinar la naturaleza de los compuestos presentes en laticíferos de tallos y frutos mediante técnicas convencionales de anatomía vegetal. Las poblaciones estudiadas no evidenciaron diferencias morfo-anatómicas significativas. Presentan hojas simples, venación pinnada broquidódroma, lámina isolateral anfiestomática, estomas braqui, anomo y anficiclocíticos, tricomas eglandulares, nervio medio con haz bicolateral y laticíferos no-articulados continuos en pecíolo, tallo y frutos. Se observan diferencias en los parámetros foliares cuantificados, sin embargo, solo la de densidad de tricomas, estomas y el espesor de cutícula se correlacionan positivamente con el gradiente altitudinal indicando plasticidad fenotípica. Se realiza por primera vez un análisis histoquímico de los laticíferos y otros idioblastos del tallo A. odorata.

Morphoanatomical and histochemical characterization of Larrea species from Northwestern of Argentina

Abstract Larrea divaricata Cav., L. cuneifolia Cav. and L. nitida Cav., Zygophyllaceae, are evergreen xerophytic shrubs occurring in Northwestern Argentina used in traditional medicine. The aim of this work was to characterize the morphology, anatomy and histochemistry of the vegetative organs of three Larrea species by light and scanning electron microscopy in order to provide supporting data for their correct identification and to determine the site of synthesis and accumulation of its main active compounds. The shape, number and percentage of coalescence of leaflets, presence or absence of mucrones and rachis and the shape of the stipules represented the main botanical differences between the studied Larrea species. Anatomically three species presented amphystomatic leaves, with thick resinous slightly striated cuticle with resinous deposits, polygonal epidermal cells with straight anticlinal walls, ciclocytic, brachy-paracytic and paracytic stomatal types, non-glandular trichomes and isolateral mesophyll. The position and abundance of the sclerenchyma at the mid vein and petiole transection allows the differentiation of the three species, been more abundant in L. cuneifolia. Secondary phloem and parenchyma cells presented abundant calcium oxalate druses and solitary rhomboidal crystals. Epidermal cells and cuticle layer of leaflets and stipules of the three species presented amber resin deposits and content which stained positively for polysaccharides, phenolic compounds, flavonoids and tannins, while mesophyll palisade cells showed small refracting droplets stained positively for lipophilic substances.