Phenotypic plasticity of growth ring traits in Pinus hartwegii at the ends of its elevational gradient.

Introduction: Phenotypic plasticity (PP) could be an important short-term mechanism to modify physiological and morphological traits in response to climate change and global warming, particularly for high-mountain tree species. The objective was to evaluate PP response of growth ring traits to temperature and precipitation in Pinus hartwegii Lindl. populations located at the ends of its elevational gradient on two volcanic mountains in central Mexico (La Malinche and Nevado de Toluca). Methods: Increment cores collected from 274 P. hartwegii trees were used to estimate their PP through reaction norms (RN), which relate the ring width and density traits with climate variables (temperature and precipitation). We estimated the trees' sensitivity (significant RN) to climatic variables, as well as the relative proportion of RN with positive and negative slope. We also estimated the relationship between the PP of ring width and density traits using correlation and Principal Component (PC) analyses. Results: Over 70% of all trees showed significant RN to growing season and winter temperatures for at least one growth ring trait, with a similar proportion of significant RN at both ends of the gradient on both mountains. Ring width traits had mostly negative RN, while ring density traits tended to have positive RN. Frequency of negative RN decreased from lower to higher elevation for most traits. Average PP was higher at the lower end of the gradient, especially on LM, both for ring width and ring density traits, although high intrapopulation variation in PP was found on both mountains. Discussion: Results indicate that P. hartwegii presents spatially differentiated plastic responses in width and density components of radial growth. PP was particularly strong at the lower elevation, which has higher temperature and water stress conditions, putting these populations at risk from the continuing global warming driven by climate change.

Pre-Germinative Treatments and Morphophysiological Traits in Enterolobium cyclocarpum and Piscidia piscipula (Fabaceae) from the Yucatan Peninsula, Mexico.

Enterolobium cyclocarpum and Piscidia piscipula are two important tree Fabaceae species distributed from the Yucatan Peninsula, Mexico. Our aims were focused on the E. cyclocarpum and P. piscipula seeds for: (1) to examine the seed permeability and imbibition rate, (2) to evaluate the effect of seed pre-germinative treatments, and (3) to characterize the structures involved on the presence of physical dormancy (PY). We used fresh seeds to determine seed permeability and imbibition rate, seed viability by means of tetrazolium test, furthermore, we applied mechanical scarification and boiler shocks for 5 s, 10 s and 15 s treatments. Morphological characterization of the seed coat was by Scanning Electron Microscope (SEM). Seed viability in E. cyclocarpum and P. piscipula were 100% and 96%, respectively. Seed permeability and imbibition rate in E. cyclocarpum were low. The highest germination in E. cyclocarpum was in the mechanical scarification (92%), while in P. piscipula, this parameter was in the 10 s boiling water treatment (76.0%). The presence of PY was confirmed in both species because they showed low seed permeability, and imbibition rate; furthermore, exhibited macrosclereids cells. The present research seeks to promote the sustainable use of E. cyclocarpum and P. piscipula.

Caracterización de la microbiota nativa del queso Oaxaca tradicional en tres fases de elaboración / Characterization of the native microflora of traditional Oaxaca cheese in three phases of production

El queso Oaxaca tradicional goza de gran reconocimiento y consumo a nivel nacional, al ser elaborado con leche cruda de vaca es considerado como factor de riesgo para la salud, sin embargo, contiene flora natural no patógena como las bacterias lácticas (BAL), que le proporciona características extraordinarias y su reconocida tipicidad siendo importante su caracterización. Se realizó el conteo, aislamiento y caracterización fenotípica (pruebas morfológicas, bioquímicas, factores de crecimiento y fermentación) de coliformes totales, BAL, levaduras y Staphylococcus spp.en las etapas de leche, cuajada y queso. Todos los recuentos se encontraron fuera de la normativa mexicana (NOM-243-SSA1-2010); se observó diferencia (p<0,05) entre la etapa de leche y queso para coliformes totales, BAL y levaduras. Se aislaron 43 cepas de BAL, 38 de coliformes, 24 de levaduras y 16 de Staphylococcus spp. El 72,1% de las BAL correspondió al género Lactococcus y el 27,9% a Lactobacillus, se detectó la presencia de E. coli, Staphylococcus aureus y Rhodotorula spp. Los resultados muestran deficientes prácticas de higiene en la elaboración de queso Oaxaca, siendo importante la identificación de la microbiota autóctona y monitoreo en toda la cadena productiva a fin de obtener un producto artesanal inocuo y de mejor calidad.

The traditional Oaxaca cheese is highly regarded nationally and its consumption, being made from raw cow’s milk is considered as a risk factor to health, however is nonpathogenic natural flora and lactic acid bacteria (LAB), which provides unique characteristics and typicality recognized to be important characterization. Count was performed, isolation and phenotypic characterization (morphological and biochemical tests, growth factors and fermentation) of total coliforms, LAB, yeasts and Staphylococcus in the stages of milk, curd and cheese. All counts were found outside Mexican standards (NOM-243-SSA1-2010), was difference (p<0.05) between the stage of milk and cheese for total coliforms, LAB and yeasts. 43 strains were isolated from BAL, coliform 38, 24 yeasts, and 16 Staphylococcus. The 72.1% of the BAL corresponded to the genus Lactococcus and 27.9% for Lactobacillus, we detected the presence of E. coli, Staphylococcus aureus, and Rhodotorula spp. The results show poor hygiene practices in Oaxaca cheese making and it is important to identify the indigenous microbiota and monitoring throughout the production chain in order to get a handmade product safe and of better quality.