Strobilus and seed production of Dioon edule (Zamiaceae) in a population with low seedling density in San Luis Potosí, Mexico

"We describe strobilus and seed development in a Dioon edule (chamal, palma, dameu') population characterized by low seedling and high adult tree density, in order to improve conservation decisions for this endangered cycad species. Female strobili required 16-17 months and male 4-5 months to develop. During this period 80% female and 100% male strobili were not damaged by herbivores. The method of cone analysis used to evaluate seed production of pines was modified for D. edule, providing actual yield of individual strobili compared to potential seed yield, explaining productivity in terms of seed efficiency, and identifying and quantifying the types of seed failures. Larger strobili have higher seed potential calculated as the number of seeds potentially produced in the fertile megasporophylls of each strobilus, total seeds actually produced, and seeds with an embryo (filled). Calculated average seed potential per strobilus was of 230.4 seeds. Using the X-ray technique, average seed traits were 100.2 full, 1.8 insect damaged, and 0.6 malformed. Seed efficiency (number of filled seeds as a percentage of the seed potential of each strobilus) of 42.5% indicated that major seed loss was attributable to abortive ovules and seeds, possibly due to ineffective pollination. Seedling survival in greenhouse conditions was 100% after one year. Low seed production affects the population structure and hinders its conservation.

Effects of shade on germination traits of the endangered cycad Dioon edule (Zamiaceae)

"The endangered cycad Dioon edule requires shade provided by filtered sunlight under the canopy of trees or maternal plants during initial growth stages. It is known that germination improves under shade, but there is no report of radiation conditions. In order to understand how photosynthetic photon flux density (PPFD) affect germination traits, we evaluated some germination indexes. A sample of three mature strobili and 200 viable seeds per strobilus were selected to evaluate seed size (length, width, and fresh weight). Two experimental treatments were established simulating shade under the oak forest canopy with PPFD 81 µmol m−2 s−1 (PPFD81), and under maternal plant canopy with PPFD 17 µmol m−2 s−1 (PPFD17), as measured previously in the study site. Means of response variables (germinability, velocity of germination, synchronization, mean germination time and relative frequency of germination) for the two treatments were compared using a t-test and a correlation analysis. No significant correlation between seed size and germination traits was detected. Germinability was higher at PPFD17 (89 %) than PPFD81 (39 %), but mean germination time was similar across treatments. The velocity of germination was greater under PPFD17 but synchronization was the opposite. The low PPFD stimulated D. edule germination, but also the spectral composition must be evaluated.""La cícada en peligro de extinción Dioon edule requiere la sombra que le proporciona el dosel o las plantas maternas al fltrar la luz del sol durante su etapa inicial de crecimiento. Se sabe que la germinación es mejor con sombra, pero no existen reportes sobre las condiciones de la radiación. Evaluamos diferentes indicadores de germinación con el propósito de entender cómo es afectada por la densidad de fujo de fotones fotosintéticos (PPFD). Una muestra de tres estróbilos maduros y 200 semillas viables por estróbilo fueron seleccionadas para evaluar el tamaño de la semilla (largo, ancho y peso fresco). Dos tratamientos experimentales se establecieron simulando la sombra bajo el dosel del encinar con densidad de fujo de fotones fotosintéticos de 81 µmol m-2 s-1 (PPFD81) y bajo las plantas maternas con densidad de fujo de fotones fotosintéticos de17 µmol m-2 s-1 (PPFD17), como se midió previamente en el sitio de estudio. La media de las variables (capacidad germinativa, velocidad de germinación, sincronización, tiempo medio de germinación y frecuencia relativa de germinación) para los dos tratamientos se compararon usando una prueba de t. Se aplicó un análisis de correlación a los datos de germinación y tamaño de semilla. Se aplicó una regresión a los predictores ambientales (temperatura, humedad relativa, densidad de fujo de fotones fotosintéticos) de la capacidad germinativa. No se detectó correlación signifcativa entre el tamaño de la semilla y las variables de germinación. La capacidad germinativa fue mayor en PPFD17 (89 %) que PPFD81 (39 %), pero el tiempo medio de germinación fue similar. La velocidad de germinación fue mayor en PPFD17 pero menor en la sincronización. El bajo PPFD estimuló la germinación de D. edule, pero también la composición espectral debe ser evaluada

Population structure of Dioon purpusii Rose in Oaxaca, Mexico

Cycads are currently suffering significant habitat loss from deforestation, agricultural expansion, and illegal harvesting. Dioon purpursii Rose has restricted distribution and small populations, which until now are endemic in the state of Oaxaca in Mexico, and it has been included in the category of threatened and vulnerable. Three sites with D. purpusii plants were located in the state of Oaxaca. Structural and dendrometric characteristics of the population and physiognomic, floristic and environmental characteristics of the forest community at each site were determined. Dendrometric variables were evaluated by an analysis of variance (ANOVA), and a similarity analysis between sites was applied to all characteristics, followed by a cluster analysis to express the relationships between sites. The population structure of the three sites is typical of species in which a great frequency of seedlings and juveniles suggests optimal microhabitat conditions for initial establishment. The results of the ANOVA showed that the most developed plants were found at Site 3, followed by Sites 1 and 2. The floristic composition corresponded to the type of tropical deciduous forest vegetation in the region, where D. purpusii formed part of the tree, shrub and herb layers. The phenogram resulting from the similarity and cluster analyses showed that Sites 1 and 2 are more similar (0.97), and Site 3 less similar to the other two (0.84). Although the population structure of D. purpusii at the three sites is similar to that found for other cycad species, the main threats are the small number of reproductive individuals, harvesting of leaves, and the constant threat of habitat alteration, like construction of roads, contributing to extinction. Key words: cycadas, Dioon purpusii, population structure, physiognomy, conservation, Oaxaca, Mexico.Cycads are currently suffering significant habitat loss from deforestation, agricultural expansion, and illegal harvesting. Dioon purpursii Rose has restricted distribution and small populations, which until now are endemic in the state of Oaxaca in Mexico, and it has been included in the category of threatened and vulnerable. Three sites with D. purpusii plants were located in the state of Oaxaca. Structural and dendrometric characteristics of the population and physiognomic, floristic and environmental characteristics of the forest community at each site were determined. Dendrometric variables were evaluated by an analysis of variance (ANOVA), and a similarity analysis between sites was applied to all characteristics, followed by a cluster analysis to express the relationships between sites. The population structure of the three sites is typical of species in which a great frequency of seedlings and juveniles suggests optimal microhabitat conditions for initial establishment. The results of the ANOVA showed that the most developed plants were found at Site 3, followed by Sites 1 and 2. The floristic composition corresponded to the type of tropical deciduous forest vegetation in the region, where D. purpusii formed part of the tree, shrub and herb layers. The phenogram resulting from the similarity and cluster analyses showed that Sites 1 and 2 are more similar (0.97), and Site 3 less similar to the other two (0.84). Although the population structure of D. purpusii at the three sites is similar to that found for other cycad species, the main threats are the small number of reproductive individuals, harvesting of leaves, and the constant threat of habitat alteration, like construction of roads, contributing to extinction. Key words: cycadas, Dioon purpusii, population structure, physiognomy, conservation, Oaxaca, Mexico

Tolerance to cadmium of agave lechuguilla (agavaceae) seeds and seedlings from sites contaminated with heavy metals

"We investigated if seeds of Agave lechuguilla from contaminated sites with heavy metals were more tolerant to Cd ions than seeds from noncontaminated sites. Seeds from a highly contaminated site (Villa de la Paz) and from a noncontaminated site (Villa de Zaragoza) were evaluated. We tested the effect of Cd concentrations on several ecophysiological, morphological, genetical, and anatomical responses. Seed viability, seed germination, seedling biomass, and radicle length were higher for the non-polluted site than for the contaminated one. The leaves of seedlings from the contaminated place had more cadmium and showed peaks attributed to chemical functional groups such as amines, amides, carboxyl, and alkenes that tended to disappear due to increasing the concentration of cadmium than those from Villa de Zaragoza. Malformed cells in the parenchyma surrounding the vascular bundles were found in seedlings grown with Cd from both sites. The leaves from the contaminated place showed a higher metallothioneins expression in seedlings from the control group than that of seedlings at different Cd concentrations. Most of our results fitted into the hypothesis that plants from metal-contaminated places do not tolerate more pollution, because of the accumulative effect that cadmium might have on them.

Desarrollo de la corteza: Estudio comparativo en dos especies de Ceiba (Malvaceae)

Background and Aims: Ceiba aesculifolia and C. pentandra (Malvaceae) are two of the four Ceiba species growing in Mexico. They are recognized as "pochotes" and have ornamental and medicinal use of their bark. In order to find distinctive attributes between these species of wide distribution in the country, a comparative study of the anatomical structure of the bark along its axes and the relationship with possible ecological adaptations were carried out. Methods: Samples from the new branches to the main trunk of four individuals were collected from the deciduous tropical forest of the State of Mexico and Puebla. Histological sections of the bark were cut with sliding microtome; the sections were stained with safranine-fast green and mounted in synthetic resin. Key results: The bark is slightly fissured to fissured on mature stems, leaden-gray color in C. aesculifolia and green in C. pentandra; with prickles. The peridermis originates from a subepidermal layer at the branch tips; as the axes increase in diameter, the rays strongly dilate (wedge-shaped) and the phloem fibers are organized in strata, characteristics shared with other Bombacoideae (Malvaceae). Ceiba pentandra maintains patches of peridermis that are alternate with epidermis, unstratified prickles and few druses (<20/mm2), while in C. aesculifolia there is a rhytidome, stratified prickles, and abundant druses (50-60/mm2). Conclusions: Details of structural changes along the axis, in addition to the differences found between both species are reported for the first time for Ceiba. The rapid differentiation of the peridermis in the ceibas studied is interpreted as an adaptation to protect against sunlight and desiccation; an aspect that has been observed in other species growing in seasonal environments.Antecedentes y Objetivos: Ceiba aesculifolia y C. pentandra (Malvaceae) son dos de las cuatro especies de Ceiba presentes en México. Se conocen como “pochotes”; sus cortezas tienen usos ornamentales y medicinales. Con la finalidad de encontrar atributos distintivos entre estas dos especies de amplia distribución en el país, se realizó un estudio comparativo de la estructura anatómica de la corteza a lo largo de sus ejes y su relación con posibles adaptaciones ecológicas. Métodos: Se recolectaron muestras desde las ramas nuevas hasta el tronco principal de cuatro individuos en un bosque tropical caducifolio de los estados de México y Puebla. Se realizaron cortes histológicos de la corteza con un microtomo de deslizamiento; las secciones se tiñeron con safranina-verde rápido y se montaron en resina sintética. Resultados clave: La corteza es ligeramente fisurada a fisurada en tallos maduros, de color gris plomizo en C. aesculifolia y verde en C. pentandra; con aguijones. La peridermis se origina de un estrato subepidérmico en los ápices de las ramas; conforme los ejes aumentan en diámetro, los radios se dilatan fuertemente (forma de embudo) y las fibras del floema se organizan en estratos, características compartidas con otras Bombacoideae (Malvaceae). Ceiba pentandra mantiene parches de peridermis que se alternan con epidermis, aguijones no estratificados y drusas escasas (<20/mm2), mientras que en C. aesculifolia hay ritidoma, aguijones estratificados y drusas abundantes (50-60/mm2). Conclusiones: Detalles de los cambios estructurales a lo largo del eje, además de las diferencias encontradas entre ambas especies se reportan por primera vez para Ceiba. La rápida diferenciación de la peridermis en las ceibas estudiadas, se interpreta como una adaptación para protección de la luz solar y la desecación; aspecto que ha sido observado en otras especies que crecen en ambientes estacionales

Usos y conocimiento tradicional de las gimnospermas en el noreste de Oaxaca, México

Background and Aims: Approximately 156 gymnosperm species divided into six families occur naturally in Mexico. Oaxaca has a high richness of gymnosperms, with 45 species, and its inhabitants have an ancient knowledge about the traditional use of this group. The present study contributes to the documentation of traditional knowledge of the gymnosperms in Oaxaca, to evaluate the importance of plant families as useful resources, to understand the relationships between ethnic groups and richness of useful species, as well as to compare our records of gymnosperms with those at state and national levels.Methods: This study was carried out in 84 municipalities within three Priority Terrestrial Regions in the northeast of Oaxaca. The ethnobotanical data were collected through participant observation, ethnobotanical fieldtrips, content-free interviews of the local guides, and botanical specimens were collected. All data were analyzed qualitatively to integrate ethnofloristic and traditional knowledge, as well as ecological aspects of species studied.Key results: We recorded 30 species belonging to the families Cupressaceae, Pinaceae, Podocarpaceae and Zamiaceae. The largest number of useful species (16) registered belongs to Pinaceae. Among the Zapotecs, uses were found for 16 different species, the Mixes use ten and the Mazatec nine. All taxa registered with any use have a common name, 71% in the local language and 97% in Spanish. The most common uses were timber, construction, ornamental and fuel. The montane cloud forest is the vegetation type with the largest number of useful gymnosperms, with 15 species. Forty-five percent of the registered taxa are endemic to Mexico, six species of Pinaceae and eight of Zamiaceae are considered endemic to Oaxaca.Conclusions: This research contributes to increase records of useful gymnosperms in the state of Oaxaca. It is necessary to reconsider and understand the local value of species within the ethnic worldview in order to preserve traditional uses and promote sustainable management programs.Antecedentes y Objetivos: En México existen alrededor de 156 especies de gimnospermas nativas pertenecientes a seis familias. Para el estado de Oaxaca, se registran 45 especies de gimnospermas y sus habitantes poseen un sobresaliente conocimiento ancestral en el uso tradicional de este grupo taxonómico. El presente estudio contribuye al registro y documentación del conocimiento tradicional de las gimnospermas en Oaxaca, a evaluar la importancia de las familias botánicas como fuente de recursos, analizar las relaciones existentes entre los grupos étnicos y la riqueza de especies útiles, así como a comparar los registros obtenidos con el número de gimnospermas a nivel nacional y estatal.Métodos: El estudio se realizó en 84 municipios en tres Regiones Terrestres Prioritarias al noreste de Oaxaca. Los datos etnobotánicos fueron recopilados mediante observación participante moderada, caminatas etnobotánicas, entrevista libre a guías locales y colecta de ejemplares botánicos. Los datos se analizaron cualitativamente para integrar el conocimiento tradicional, etnoflorístico y los aspectos ecológicos de las especies.Resultados clave: Se registraron 30 especies de las familias Cupressaceae, Pinaceae, Podocarpaceae y Zamiaceae. El mayor número de especies útiles (16) registradas pertenece a Pinaceae. Entre los zapotecos se encontraron usos para 16 diferentes especies, los mixes utilizan diez y los mazatecos nueve. Todos los taxa registrados tienen nombre común, 71% en lengua local y 97% en español. Los usos más frecuentes fueron el maderable, la construcción, el ornamental y el combustible. El bosque mesófilo de montaña es el tipo de vegetación del área estudiada que contiene el mayor número de gimnospermas útiles, con 15 especies. De los taxa registrados 45% son endémicos de México, seis especies de Pinaceae y ocho de Zamiaceae se consideran endémicos de Oaxaca.Conclusiones: Este estudio incrementa los registros sobre gimnospermas útiles en el estado de Oaxaca. Se requiere reconsiderar y entender el valor local de estas especies dentro de la cosmovisión étnica, para preservar los usos tradicionales y promover programas de manejo sostenible

The Endangered Species <em>Dioon edule</em> in the Sierra Madre Oriental in San Luis Potosí: Demography and Genetic Diversity

The distribution of the endangered species Dioon edule is in populations scattered throughout the Sierra Madre Oriental in San Luis Potosí, Mexico. Its habitat is tropical dry forests at lower elevations and oak forests at higher elevations, mainly disturbed by anthropic activities. We determined and analyzed nine populations’ demographic structure and explored the genetic diversity of five using SSR markers. The population density averaged 2050 individuals ha-1 and have an aggregated distribution pattern. Differences in the plants’ size among localities are due to site quality, based on their adaptation capacity and response to climate and soil traits. Most populations have the highest mortality in the early stages of life, with a low mortality rate for those who survive this bottleneck. Two populations have a relatively constant mortality rate, attributed to disturbance of the habitat. The populations show low genetic diversity and an excess of homozygotes. Their similarity is probably related to the formation of natural corridors favoring connectivity between populations. The deterioration and fragmentation of the habitat have severe effects on the populations’ viability, like reducing gene flow, which has led to inbreeding and genetic drift

Tomar la palabra (II). Intertextualidad e intermedialidad como herramientas pedagógicas para la enseñanza de la literatura y otros discursos

Este proyecto explora las relaciones entre obras literarias y literatura y otras artes (música, pintura, fotografía, cine, etc.) como medio para desarrollar la competencia lectora y expresiva y estimular el disfrute literario en ámbito universitario

Clonal chromosomal mosaicism and loss of chromosome Y in elderly men increase vulnerability for SARS-CoV-2

The pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2, COVID-19) had an estimated overall case fatality ratio of 1.38% (pre-vaccination), being 53% higher in males and increasing exponentially with age. Among 9578 individuals diagnosed with COVID-19 in the SCOURGE study, we found 133 cases (1.42%) with detectable clonal mosaicism for chromosome alterations (mCA) and 226 males (5.08%) with acquired loss of chromosome Y (LOY). Individuals with clonal mosaic events (mCA and/or LOY) showed a 54% increase in the risk of COVID-19 lethality. LOY is associated with transcriptomic biomarkers of immune dysfunction, pro-coagulation activity and cardiovascular risk. Interferon-induced genes involved in the initial immune response to SARS-CoV-2 are also down-regulated in LOY. Thus, mCA and LOY underlie at least part of the sex-biased severity and mortality of COVID-19 in aging patients. Given its potential therapeutic and prognostic relevance, evaluation of clonal mosaicism should be implemented as biomarker of COVID-19 severity in elderly people. Among 9578 individuals diagnosed with COVID-19 in the SCOURGE study, individuals with clonal mosaic events (clonal mosaicism for chromosome alterations and/or loss of chromosome Y) showed an increased risk of COVID-19 lethality

Effects of shade on germination traits of the endangered cycad <em>Dioon edule</em> (Zamiaceae)

"The endangered cycad Dioon edule requires shade provided by filtered sunlight under the canopy of trees or maternal plants during initial growth stages. It is known that germination improves under shade, but there is no report of radiation conditions. In order to understand how photosynthetic photon flux density (PPFD) affect germination traits, we evaluated some germination indexes. A sample of three mature strobili and 200 viable seeds per strobilus were selected to evaluate seed size (length, width, and fresh weight). Two experimental treatments were established simulating shade under the oak forest canopy with PPFD 81 µmol m−2 s−1 (PPFD81), and under maternal plant canopy with PPFD 17 µmol m−2 s−1 (PPFD17), as measured previously in the study site. Means of response variables (germinability, velocity of germination, synchronization, mean germination time and relative frequency of germination) for the two treatments were compared using a t-test and a correlation analysis. No significant correlation between seed size and germination traits was detected. Germinability was higher at PPFD17 (89 %) than PPFD81 (39 %), but mean germination time was similar across treatments. The velocity of germination was greater under PPFD17 but synchronization was the opposite. The low PPFD stimulated D. edule germination, but also the spectral composition must be evaluated.""La cícada en peligro de extinción Dioon edule requiere la sombra que le proporciona el dosel o las plantas maternas al fltrar la luz del sol durante su etapa inicial de crecimiento. Se sabe que la germinación es mejor con sombra, pero no existen reportes sobre las condiciones de la radiación. Evaluamos diferentes indicadores de germinación con el propósito de entender cómo es afectada por la densidad de fujo de fotones fotosintéticos (PPFD). Una muestra de tres estróbilos maduros y 200 semillas viables por estróbilo fueron seleccionadas para evaluar el tamaño de la semilla (largo, ancho y peso fresco). Dos tratamientos experimentales se establecieron simulando la sombra bajo el dosel del encinar con densidad de fujo de fotones fotosintéticos de 81 µmol m-2 s-1 (PPFD81) y bajo las plantas maternas con densidad de fujo de fotones fotosintéticos de17 µmol m-2 s-1 (PPFD17), como se midió previamente en el sitio de estudio. La media de las variables (capacidad germinativa, velocidad de germinación, sincronización, tiempo medio de germinación y frecuencia relativa de germinación) para los dos tratamientos se compararon usando una prueba de t. Se aplicó un análisis de correlación a los datos de germinación y tamaño de semilla. Se aplicó una regresión a los predictores ambientales (temperatura, humedad relativa, densidad de fujo de fotones fotosintéticos) de la capacidad germinativa. No se detectó correlación signifcativa entre el tamaño de la semilla y las variables de germinación. La capacidad germinativa fue mayor en PPFD17 (89 %) que PPFD81 (39 %), pero el tiempo medio de germinación fue similar. La velocidad de germinación fue mayor en PPFD17 pero menor en la sincronización. El bajo PPFD estimuló la germinación de D. edule, pero también la composición espectral debe ser evaluada