Soil microorganisms are critical players in plant-soil interactions at the rhizosphere. We have identified a Bacillus megaterium strain that promoted growth and development of bean (Phaseolus vulgaris) and Arabidopsis thaliana plants. We used Arabidopsis thaliana as a model to characterize the effects of inoculation with B. megaterium on plant-growth promotion and postembryonic root development. B. megaterium inoculation caused an inhibition in primary-root growth followed by an increase in lateral-root number, lateral-root growth, and root-hair length. Detailed cellular analyses revealed that primary root-growth inhibition was caused both by a reduction in cell elongation and by reduction of cell proliferation in the root meristem. To study the contribution of auxin and ethylene signaling pathways in the alterations in root-system architecture elicited by B. megaterium, a suite of plant hormone mutants of Arabidopsis, including aux1-7, axr4-1, eir1, etr1, ein2, and rhd6, defective in either auxin or ethylene signaling, were evaluated for their responses to inoculation with this bacteria. When inoculated, all mutant lines tested showed increased biomass production. Moreover, aux1-7 and eir1, which sustain limited root-hair and lateral-root formation when grown in uninoculated medium, were found to increase the number of lateral roots and to develop long root hairs when inoculated with B. megaterium. The ethylene-signaling mutants etr1 and ein2 showed an induction in lateral-root formation and root-hair growth in response to bacterial inoculation. Taken together, our results suggest that plant-growth promotion and root-architectural alterations by B. megaterium may involve auxin- and-ethylene independent mechanisms.

Our results show that Sorghum bicolor is able to recognize bacteria through its volatile compounds and differentially respond to beneficial or pathogens via eliciting nutritional or defense adaptive traits. Plants establish beneficial, harmful, or neutral relationships with bacteria. Plant growth promoting rhizobacteria (PGPR) emit volatile compounds (VCs), which may act as molecular cues influencing plant development, nutrition, and/or defense. In this study, we compared the effects of VCs produced by bacteria with different lifestyles, including Arthrobacter agilis UMCV2, Bacillus methylotrophicus M4-96, Sinorhizobium meliloti 1021, the plant pathogen Pseudomonas aeruginosa PAO1, and the commensal rhizobacterium Bacillus sp. L2-64, on S. bicolor. We show that VCs from all tested bacteria, except Bacillus sp. L2-64, increased biomass and chlorophyll content, and improved root architecture, but notheworthy A. agilis induced the release of attractant molecules, whereas P. aeruginosa activated the exudation of growth inhibitory compounds by roots. An analysis of the expression of iron-transporters SbIRT1, SbIRT2, SbYS1, and SbYS2 and genes related to plant defense pathways COI1 and PR-1 indicated that beneficial, pathogenic, and commensal bacteria could up-regulate iron transporters, whereas only beneficial and pathogenic species could induce a defense response. These results show how S. bicolor could recognize bacteria through their volatiles profiles and highlight that PGPR or pathogens can elicit nutritional or defensive traits in plants.

Iron (Fe) is an essential element for plant growth and development. Some plant growth-promoting rhizobacteria can increase Fe uptake by plants through reduction of Fe(III) to Fe(II) at the root surface. The aim of this work was to identify novel bacterial strains with high Fe(III) reduction ability and to evaluate their role in plant Fe uptake. Four bacterial strains (UMCV1 to UMCV4) showing dissimilatory Fereducing activity were isolated from the rhizosphere of bean and maize plants and further identiWed by 16S rDNA ampliWcation and sequence analysis. From these analyses, UMCV1 and UMCV2 isolates were identiWed as Bacillus megaterium and Arthrobacter spp., respectively, whereas UMCV3 and UMCV4 were identiWed as Stenotrophomonas maltophilia. All four isolates showed Fe reduction in a nonXooded soil and when associated with roots of bean plants grown in alkaline soil or in mineral medium. In addition, the bacterial isolates were able to stimulate plant growth in vitro and on a broad level, plants grown in inoculated soil were generally bigger and with higher Fe content than those grown in sterilized soil. These results indicate that bacterial species isolated from the rhizosphere of bean and maize plants contribute signiWcantly to Fe uptake by plants likely through increased Fe(III) reduction in the rhizosphere.

Question Along an altitudinal gradient of 2000 m in a semi‐tropical mountain, we explored the relation between tree specific diversity and community functional composition by studying variations in tree allometry, stem and leaf functional traits, and their relationship with temperature and precipitation. Location Tequila Volcano, Jalisco, Mexico (20°48′ N, 103°51′ W). Methods We surveyed tree specific diversity, five forest structural parameters and six functional traits in ten horizontal transects (50–75 m in length) located every 200 m along a 2000‐m gradient (from 800 to 2800 m a.s.l.). We calculated alpha and beta diversity, and quantified the community‐weighted means for wood and bark density, Huber value (sapwood to leaf area ratio), leaf area, leaf dry mass content and leaf mass per unit area. The patterns of association were explored using Pearson correlations, and summarized using PCA. Results Alpha diversity was independent of altitude, and species turnover was almost complete between consecutive transects. Altitude (and its associated abiotic factors, temperature and precipitation) were highly correlated with functional traits. Maximum tree height, total basal area and the community‐weighted mean values for leaf mass per unit area, leaf dry mass content, and the Huber values were positively correlated with altitude, and the opposite was found for the number of basal stems. Stem and leaf trait values were correlated along the altitudinal gradient. Conclusions Altitude imposes environmental filters at the community scale that determine a high species replacement. Stem and leaf traits were correlated along the gradient; trees at higher altitudes were taller with a single stem, higher density of wood and bark, and leaves with higher leaf mass per area and dry mass content than in the low‐altitude sites. These results suggest the consistency of a fast–slow acquisitive trade‐off across environments, tending to promote slow acquisition and high longevity at higher altitudes.

In tropical latitudes, the analysis of leaf phenology in tree species of lineages with temperate origin can help better understanding the potential effects of climate change on these forests. Over three years (2008–2010), we recorded the timing of bud burst (BB), leaf unfolding (LU), and leaf spreading (LS) and their relation to temperature, precipitation, and soil water potential in two deciduous oak species (Quercus magnoliifolia Née and Quercus resinosa Liebm.) along an altitudinal gradient at the Tequila Volcano, central Mexico. Quercus magnoliifolia was monitored at three altitudes, 1450, 1667, and 1787 m, and Q. resinosa was monitored at 1787, 2055, and 2110 m. The onset of BB, LU, and LS occurred earlier at lower elevations with higher temperature in Q. magnoliifolia, but in Q. resinosa only the onset of BB occurred later at lower elevations with higher temperature. BB, LU, and LS were not correlated with rainfall and soil water potential in the two species. The total duration time of leaf development was not significantly correlated with rainfall in Q. magnoliifolia, but a significant negative correlation with rainfall was found in Q. resinosa. Results indicated that leaf phenology of the two examined oak species exhibited contrasting responses to temperature and precipitation.

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Resumen. Se presentan evidencias morfológicas y moleculares para reconocer a Centruroides limpidus tecomanus Hoffmann (Scorpiones: Buthidae) como especie válida y no como una subespecie de Centruroides limpidus (Karsch). Se diagnostica la especie. Palabras clave: escorpiones, taxonomía, rango específi co, Centruroides limpidus, subespecies.

Introduction: Non-communicable diseases (NCD) are the leading cause of mortality in the world. Among NCD varieties, obesity is a public health problem around the world, but it is especially important in poor or developing countries. The aim of this study is to explore the body composition, physical activity and food diversity in university students from Morelia, Mexico. Method: A cross sectional study was conducted with 422 students of university level. We used bioimpedance and anthropometry to determine the body composition of the students. The physical activity was analyzed by the International Physical Activity Questionnaire (IPAQ), while the food diversity was assessed by the guidelines for measuring household and individual dietary diversity of the Food and Agriculture Organization. Results: A matrix of 16 anthropometric variables was reduced to three principal components with a variance accumulate of 88.04% to women and 78.9% to men. We were able to separate groups of women based on anthropometric variables. In men, the percentage of muscle is the variable that most influences the separation of groups. The physical activity ranges from moderate to high; on average it was 5028.4 and 4449.4 MET-minutes/week for men and women respectively. A high food diversity and equitability of consumption was found, the socioeconomic level of the students does not allow inferring food insecurity. In men we found more associated variables than in women and we found no relationship with dietary diversity. We found statistically significant relationships between chronological age and metabolic age in both sexes, but we did not find a relationship between actual weight and ideal weight. Conclusion: In conclusion, we describe the body composition, anthropometry, physical activity and food diversity of university students.