Endospermic seeds may germinate more successfully than non-endospermic seeds. The quantity of reserves of endosperm is directly related to seed size; large seeds may present faster and higher percentages of germination than small seeds. We investigate whether capacity and time of germination differ between seeds with and without endosperm in two species of Brassicaceae (Lepidium virginicum and Brassica rapa) and two species of Fabaceae (Crotalaria pumila and Medicago sativa). We also investigate whether seed size within each seed type infl uences the percentage and time of germination. Seeds were collected from populations of these species, weighed and classifi ed as large or small. Large and small seeds of species of both families, with both endospermic and non-endospermic seeds, were germinated under controlled conditions. Endospermic Brassicaceae seeds presented a higher percentage of germination than the non-endospermic seeds; however germination times were similar between seed type and seed size. Non-endospermic seeds of Fabaceae germinated more than the endospermic seeds of the same family, non-endospermic seeds also germinate faster. Regardless of the presence of endosperm, large seeds presented a higher percentage of germination than small seeds. However, it is not possible to generalize that seeds with endosperm will be of greater size and thus present higher percentages of germination, since the species of Fabaceae do not fi t this pattern. It is inferred that the endosperm acts as a storage tissue in Brassicaceae, while in Fabaceae it may function more as a protective barrier for the embryo, but confi rmation of this would require further research. Key words: Brassicaceae, cotyledons, dicotyledons, embryo, Fabaceae.Resumen: Semillas endospérmicas tendrían una germinación más exitosa que semillas no endospérmicas. La cantidad de reservas del endospermo guarda una relación directa con el tamaño de las semillas; semillas grandes tendrían mayor porcentaje y tasa de germinación que semillas pequeñas. Investigamos si el porcentaje y el tiempo de germinación difi ere entre semillas con y sin endospermo en dos especies de Brassicaceae (Lepidium sativum y Brassica rapa) y dos especies de Fabaceae (Crotalaria pumila y Medicago sativa). Se investigó también si el tamaño de las semillas dentro de cada tipo de semilla infl uye en su porcentaje y tiempo de germinación. Se colectaron semillas de poblaciones de las especies mencionadas, se pesaron y se clasifi caron en semillas chicas y grandes. Las semillas chicas y grandes de especies con semillas endospérmicas y no endospérmicas de ambas familias se germinaron en condiciones controladas. Las semillas endospérmicas de Brassicaceae tuvieron mayor porcentaje de germinación que las no endospérmicas, sin embargo el tiempo de germinación fue similar entre tipo y tamaños de semillas. Las semillas no endospérmicas de Fabaceae germinaron más y más rápido que las semillas endospérmicas de la misma familia. Independientemente de la presencia de endospermo, las semi...

Background Density in inter and intraspecific plant-plant interactions affects the action modes of allelopathy (autotoxicity, negative and positive allelopathy). Some seeds exude compounds that inhibit the germination of others. Ipomoea murucoides and I. pauciflora are sympatric tree species that form patches at the local scale where one or the other dominates, possibly due to allelopathy in the seeds. The objective of this study was to determine the possible density-dependence of the allelopathic effect among seeds of these species through the measure of seed germination and seedling emergence. Methods In both species, allelopathy was measured as: a) germination in mixed sowing of both species at different proportions, b) germination in single-species trials at different densities after adding seed extracts of both species, and c) seedling emergence in seed mixtures of both species sown at different proportions beneath canopies of the two Ipomoea species. Results Seed germination of I. murucoides was increased by the presence of I. pauciflora and diminished at higher densities of its own seeds; however, seed germination of I. pauciflora was not affected by the presence of I. murucoides seeds. The addition of extracts (either from conspecifics or congeneric) diminished the germination of both species and at higher seed densities the germination was lower. Seedling emergence did not depend on the species under which the seeds were sown nor on the density of the seeds. Conclusions The germination experiments evidenced positive allelopathy and/or autotoxicity, while there was no evidence of allelopathic effects in seedling emergence. The allelopathic activity is reported in the seeds of these species for the first time.

El área de estudio, la Barranca Tepecapa de aproximadamente 3.5 km de longitud, se ubica dentro de la zona núcleo “Las Mariposas” en el Corredor Biológico Chichinautzin del estado de Morelos. Se realizaron colectas periódicas durante un año y medio, de octubre 2009 a abril 2011. Se colectaron 1018 ejemplares de Pteridofitas y afines, Gimnospermas y Angiospermas, pertenecientes a 99 familias, 266 géneros y 434 especies. Las familias mejor representadas son: Asteraceae, Fabaceae, Poaceae, Orchidaceae, Pteridaceae, Solanaceae y Bromeliaceae. Asimismo, se registran y describen tres tipos de vegetación para el área de estudio. Dos géneros (Amyris y Dasylirion) y 16 especies son nuevos registros para el estado de Morelos.

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Nine new records of flowering plants are reported for Morelos state, Mexico. Most of the species occur at the Biological Corridor Chichinautzin and the Biosphere Reserve Sierra of Huautla, located at north and south of Morelos state, respectively. A brief diagnosis, phenology, notes and illustrations are included. These records are the outcome of floristic studies carried out by the authors in both natural reserves.