Background and Aims: Leaf architecture and anatomy in the Asteraceae family are extremely diverse and have been studied from ecological, physiological and evolutionary perspectives. The aims of this study are to describe in detail leaf architecture and anatomy for 61 species belonging to 13 tribes of Asteraceae inhabiting a xerophytic scrub in Mexico City, Mexico and to discuss characters common to these tribes.Methods: Mature and undamaged leaves of 61 species of Asteraceae were collected in southwestern Mexico City in the “Reserva Ecológica del Pedregal de San Ángel” (REPSA). Standard anatomical techniques were used to obtain permanent slides of cleared leaves and transverse and paradermal sections. The permanent slides were analyzed to describe leaf architecture and anatomy by tribe following the standard terminologies.Key results: The results show a significant variation in leaf architecture although pinnate venation, brochidodromous secondary venation, areoles moderately developed and looped ultimate marginal venation predominate in the material studied. For anatomy, the most common traits are the striate cuticle, occurrence of trichomes and glands, as well as collateral vascular bundles with a parenchymatous sheath with girders in the Asteraceae present in this xerophytic scrub. There are no unique combinations of leaf characters for the family or any tribe.Conclusions: Leaf diversity in the family and within each tribe is consistent with some previous reports. Anatomical descriptions are a fundamental piece of the evolutionary, ecological and physiological studies in Asteraceae. The results of this descriptive study will allow testing hypotheses about the factors causing leaf diversity in this plant lineage. More leaf anatomical studies of the family are necessary to confirm the patterns proposed for the tribes and the family.

Surface and some anatomical characteristics of mature cypselae in four genera and 12 species members of the subtribe Leiboldiinae were analyzed, through light and scanning electron microscopy, with the aims of testing their diagnostic value in the taxonomical delimitation, and for this reason also studied related genera of Vernonieae which corresponds to 13 genera and 15 species grouped in seven subtribes. In addition to performing a detailed description of cypselae surface and anatomical characteristics, their potential taxonomical value is discussed. Most Leiboldiinae have prismatic cypselae, but when combined with the number of ribs and surface characteristics, species or genera can be identified. For example, Stramentopappus has obovate glabrous cypselae without a carpopodium compared with the other members of this subtribe. Bolanosa has a sericeous glandular indumentum, and Leiboldia has glands at the base of the cypselae and reticulate primary sculpture. The species of Leiboldiinae and other subtribes of Vernonieae here studied with crystals have prismatic ones contrary to the ones previously described for the Neotropical Vernonieae that were considered raphides.

Antecedentes y Objetivos: Se realizó un estudio del complemento de tricomas en las hojas de Senecio sección Mulgediifolii utilizando microscopía de luz y microscopía electrónica de barrido, con el propósito de determinar caracteres que faciliten la identificación de sus especies.Métodos: Se estudió el tercio medio de la lámina de hojas recolectadas en campo o tomadas de ejemplares de herbario. El material proveniente de herbario se hidrató en agua hirviendo y se aclaró con hidrato de cloral por varios días; el material recolectado en campo se fijó con FAA y posteriormente se conservó en alcohol etílico a 70%. Con ambos tipos de materiales se hicieron cortes transversales a mano alzada y se montaron en gelatina glicerinada. El material observado en el microscopio electrónico de barrido fue deshidratado, se llevó a punto crítico y se cubrió con polvo de oro.Resultados clave: Todas las especies de la sección presentan tricomas multicelulares uniseriados, los cuales pueden ser glandulares o no glandulares. Se identificaron seis tipos básicos de tricomas y dos subtipos, los cuales variaron de acuerdo con su posición en la lámina, con diferencias tanto en ornamentación como en depósitos de cera. Dos tipos de tricomas y una variante fueron distintivos de algunas especies; por ejemplo, la variante 2a1 es característica de Senecio jacalensis y está presente en ambas superficies foliares, el tricoma 3d se encuentra solamente en la vena media de la superficie abaxial de S. polypodioides y el tricoma 4a solamente se localiza en el margen foliar de S. roseus.Conclusiones: La combinación de caracteres, como los tipos de tricomas, su ornamentación y la presencia de cera, pueden ser útiles para diferenciar las especies de Senecio sección Mulgediifolii.

The foliar architecture of 18 genera (Barkleyanthus, Digitacalia, Erechtites, Nelsonianthus, Packera, Pentacalia, Pippenalia, Pittocaulon, Psacaliopsis, Psacalium, Pseudogynoxys, Robinsonecio, Roldana, Senecio, Telanthophora, Tetradymia, Villasenoria and Werneria) of the tribe Senecioneae (Asteraceae) distributed in Mexico is described. The aim was to identify leaf characters to be used in the taxonomy and phylogenetics of the tribe, as well as a source to identify at the generic rank the genera distributed in Mexico. More than 400 specimens were revised and several leaves were cleared to analyze leaf venation patterns. Four patterns of primary venation (actinodromous suprabasal, paralelodromous, pinnate and radiate-palmate) and five patterns of secondary venation (brochidodromous, weak-brochidodromous, craspedodromous, mixed-craspedodromous and festooned-semi-craspedodromous) were identified. Terminal tracheids were observed only in veinlets of Pentacalia, Pseudogynoxys and Werneria. In addition, secretory canals and crystals occurred in several genera. Foliar architecture showed to be a useful tool to identify genera, an identification key based mostly on leaf architecture characters is provided.

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Resumen: Para conocer los cambios que ocurren durante el desarrollo del patrón de venación e identifi car si la forma de la lámina determina el patrón de venación en miembros de la tribu Senecioneae (Asteraceae), en este trabajo se describió y comparó el desarrollo del patrón de venación durante la expansión de la hoja de Packera sanguisorbae, Psacalium peltatum, Roldana angulifolia y R. lineolata, cuyas morfologías son contrastantes (formas redondas vs. elípticas, y láminas no divididas vs. fuertemente lobuladas). Se recolectaron desde ápices vegetativos hasta hojas completamente desarrolladas y se aclararon con una mezcla de fucsina básica-NaOH para la observación de la venación. Los resultados mostraron que el tipo de margen, la disección de la lámina y el patrón de venación (venas primarias y secundarias), se establecen en estadios tempranos del desarrollo, cuando la lámina cuenta con alrededor del 3% de su longitud; la forma de la lámina se establece en etapas posteriores. El desarrollo de las venas tuvo un arreglo jerárquico como en otros taxa. Sin embargo, los órdenes de venación difi eren entre lóbulos y dientes. Los lóbulos son irrigados sólo por venas de primer y segundo orden, mientras que en los dientes pueden llegar venas hasta de séptimo orden. Con la forma de la hoja se pudo predecir el patrón de venación, excepto en aquellas de forma elíptica. En las especies de Packera, el patrón de venación semicraspedódromo festoneado se mantiene, sin importar si la lámina está o no dividida. Se concluye que el establecimiento temprano del patrón de venación y la forma de la hoja son caracteres de potencial importancia taxonómica en la tribu Senecioneae. Palabras clave: dientes, expansión de la hoja, lóbulos, órdenes de venación, Packera, Psacalium, Roldana. Abstract:The venation pattern development was described and evaluated during leaf expansion in Packera sanguisorbae, Psacalium peltatum, Roldana angulifolia, and R. lineolata of the Senecioneae tribe (Asteraceae) with contrasting morphologies (round versus elliptical shape, and entire versus deeply lobed lamina). The aims of this study were to identify the changes that occur during the venation pattern development and to determine if lamina shape correlates with the venation pattern. Leaves of different ages from meristematic apexes to fully developed leaves were collected and cleared with a basic fuchsin-NaOH mixture. The results showed that type of margin, dissection of lamina, and the venation pattern (primary and secondary veins) are fi xed since early stages of the development, when the lamina counts on 3% of its length. However, lamina shape is acquired later in development. Veins development followed a hierarchical pattern as described for other taxa. However, venation orders varied between lobes and teeth. Lobes are irrigated by primary and secondary veins, while up to 7 th orden veins are found in the teeth. Leaf shape may predict the venation pattern except when the leaf has an elliptic shape. In Packera the festooned semicraspedodromous venation...

The aims of this study were to describe and illustrate cypselae of 15 Mexican species of Mutisieae from observations using optical and scanning electron microscopy. The cypselae are heteromorphic with pilose, sericeous or glandular indumentum. The primary sculpture of the surface has two microstructural patterns: reticulate and plicate. The secondary sculpture is striate in 13 taxa, but in two species, Chaptalia estribensis and C. mexicana, differences were found in the secondary sculpture of the external and internal cypselae. The most distinctive anatomical trait is in the epicarp, which has rectangular or square-shaped cells that have a convex periclinal wall in most species of Chaptalia. The mesocarp has vascular bundles with fibers in all species of Chaptalia, but fibers are absent in Adenocaulon, Gerbera and Leibnitzia. In addition, the cells of the mesocarp inner layer have either thick walls or only an anticlinal wall in nine species of Chaptalia. The micromorphological characteristics of the primary or secondary sculpture of the surface, the type of trichomes and the variation they present have taxonomical value for recognizing closely-related taxa, whereas anatomical traits of the mesocarp distinguish Adenocaulon, Gerbera and Leibnitzia from most Chaptalia species.

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