We studied morphological changes over time by nodules formed on the root system of the common bean (Phaseolus vulgaris L.). Two cultivars, Bayomex and Cacahuate 72 with growth habit Type I and the Rhizobium etli strain CE-3 were used. The results showed the collapse of the infected zone, degradation of the cell walls and membranes, changes in the number and distribution of the starch granules, appearance of protein granules, and disintegration of the central tissue of the nodule with ageing. Additionally, we describe the influence of time on the progress of the nodular senescence.

Currently, some concerns regarding the potential toxicity of nanoparticles (NP) on the environment have emerged. The effect of ZnO, TiO2, and Fe2O3 NP on corn (Zea mays L.), common beans (Phaseolus vulgaris L.), nanobioremediation of polycyclic aromatic hydrocarbons (PAH), and soil organisms from agricultural or forest soils was studied at laboratory, greenhouse, and land level. The samples were analyzed by X-ray diffraction (XRD), field emission scanning electron microscopy with X-ray energy dispersion spectrometry (FESEM-EDS), scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS) gas chromatography (GC), ultra-performance liquid chromatography coupled to mass spectrometry (UPLC-MS) and Fourier transform infrared spectrometry with attenuated total reflectance (FTIR-ATR). ZnO-NP did not harm the mycorrhizal root colonization but, the presence of ZnO-NP decreased the degradation of PAH. The synthesis of metabolites from corn was more affected by the PAH than by ZnONP. FTIR spectra showed that NP affected the synthesis of compounds from specific functional groups in common bean plants. Fe2O3-NP were attached to the body of forestsoil organisms and significantly increased the concentration of Fe in their body, while TiO2-NP changed the morphological tissue of roots and stems of common bean as witnessed by micrographs of longitudinal and cross-sections. The NP used in this research significantly changed some response variables on the experiments carried-out at laboratory, greenhouse, and land level.

The removal of PAHs was stimulated by wastewater sludge in an alkaline saline soil of the former Lake Texcoco, but not always to the same extent. We investigated how a varying electrolytic conductivity (EC) affected the removal of phenanthrene (PHEN) and anthracene (ANTHR) from wastewater sludge-amended soils. Soil with EC 6, 30, 80, and 146 dS m -1 was contaminated with PHEN and ANTHR and amended with or without wastewater sludge, while emissions of CO 2 and concentrations of ammonium, nitrite, and nitrate were monitored. A decrement on the concentrations of PHEN and ANTHR was observed and was faster in soil with EC 6 dS m -1 than in soil with EC 30 dS m -1 and 80 dS m -1, and was slower than in soil with EC 146 dS m -1 . Adding wastewater sludge to soil reduced the concentration of PHEN and ANTHR in soil after 56 days. Spiking soil with PAHs or amending it with wastewater sludge increased the CO 2 emission rate, but decreased at higher EC. The concentration of NO 3 -decreased when soil was spiked with PAHs and amended with sludge, except in soil with EC 146 dS m -1. It was found that the removal of PAHs was not inhibited by salt content and a principal component analysis indicated that none of the measured soil characteristics, i.e., pH, EC, particle size distribution, water-holding capacity, or organic C content predicted the removal of ANTHR or PHEN from contaminated soil. The application of wastewater sludge increased the dissipation of PHEN and ANTHR after 56 days.

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<p><strong>Background. </strong>Pitayeras are traditional agroforestry harvesting systems that have been poorly studied but can harbor a diversity of trees and shrubs as in tropical dry forest (TDF). <strong>Objective. </strong> We described the diversity of woody communities<strong> </strong>in <em>Pitayeras</em> of the Sierra de Huautla to identify their importance in the conservation of TDF species. <strong>Methodology. </strong>150 plots with a defined area (10 x 10 m) divided into three <em>Pitayeras</em> (Plain, Hillside, and Orchard) were sampled. All individuals with a diameter ≥ 1 cm were quantified, and all species were identified. The alpha (H ', ⁰D, ¹D, ²D) and the beta (Bray-Curtis) diversity were estimated. A tree classification was performed to classify the plant communities of the <em>Pirayeras</em>. <strong>Results. </strong>57 species and 22 families were identified, which Fabaceae, Burseraceae, and Cactaceae were the most diverse. The most dominant species were <em>Euphorbia schlechtendalii</em>, <em>Stenocereus stellatus</em> and <em>Mimosa polyantha</em>. La Huerta was the most diverse <em>Pitayera</em>, while the Plain had the least diversity. The Plain and Orchard were the most similar <em>Pitayeras</em>. <strong>Implications</strong>. The diversity of trees and shrubs of the <em>Pitayeras</em> might be associated with particular edaphic, climatological and management conditions; however, these socio-ecological elements were not monitored. <strong>Conclusions.</strong> The <em>Pitayeras</em> harbor a diversity of trees and shrubs similar to the DTF of the Sierra de Huautla Biosphere Reserve and other parts of Mexico.</p>