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This study evaluated the survival of the grass Leersia hexandra (Lh) to the stress caused by crude oil (CO), by means of synthesis of reactive oxygen species, antioxidants in leaf-root, and by the rhizospheric bacterial activity of Lh. The experiment was carried out for 180 days, a 4x2 factorial arrangement was applied, four concentrations of CO and two technologies [phytoremediation (PH) with Lh and natural attenuation (NA) with native microorganisms]. The results recorded treatment means with statistical differences (Duncan p ≤ 0.05). Concentrations of 90 g/kg stimulated the formation of young plants (YP) and grass root. In YP leaves, the biosynthesis of H2O2, total phenols (TP) and total flavonoids (TFV) increased due to the effect of CO, as did catalase (CAT) and phenylalanine ammonia lyase (PAL) in roots. Grass roots with low H2O2 synthesis but high synthesis of CAT and PAL are a signal of tolerance to abiotic stress. Rhizosphere of Lh stimulated microbial activity and the population of Azotobacter spp but removal 22% de 90 g/kg the CO, and AN 58%. The results suggest adaptation of Lh to the stress caused by soil contaminated with oil, manifested by regulating the synthesis of H2O2 and antioxidants in leaf-root during the removal of hydrocarbons from oil.

Soil contamination with petroleum hydrocarbons affects plants and rhizospheric microorganisms. A nine-month experiment was set up to study the effect over time of oil on plant height, new plant production, plant matter production, and the population of rhizospheric microorganisms in the sedge Eleocharis palustris. The removal of total petroleum hydrocarbons from the soil was also evaluated. The results showed that plants responded differently depending on age and petroleum concentration. Concentration of 60 g of petroleum per kg of soil induced a significant increase in height (weeks 28 to 38) and new plant production (weeks 13 to 38). At the end of the evaluation period, a high petroleum concentration induced a significant increase in the number of primary roots, root and aerial dry matter, population of microalgae, total fungi, actinomycetes, Pseudomonas spp and hydrocarbonoclastic bacteria. Physiological and microbiological hormetic index values ≥1 showed a linear response to petroleum concentration in plant height and new plant production from weeks 3 and 2 to 38, respectively. A similar response curve was found for the number of primary roots, root and aerial dry matter, microalgae, total fungi, actinomycetes, Pseudomonas, and hydrocarbonoclastic bacteria (week 38). After 38 weeks of exposure to petroleum-contaminated soil, the rhizosphere of E. palustris showed petroleum removal percentages of 71, 72, 56, 42, 33 and 23% in soil that initially contained 3, 15, 30, 45, 60 and 75 g oil, respectively. The increase in petroleum removal was significantly and negatively correlated with the populations of microalgae, actinomycetes, Pseudomonas bacteria and hydrocarbonoclast bacteria.

La producción citrícola depende principalmente en la disponibilidad de portainjertos sanos, apropiados y vigorosos; parte de su reproducción está asociada con el uso de fertilizantes químicos, que contribuyen en la contaminación de los ecosistemas. El uso de fertilizantes orgánicos son alternativas para reducir el uso de fertilizantes químicos. El objetivo de este trabajo fue evaluar el efecto de tres fertilizantes orgánicos (estiércol de gallina, cachaza (1 y 2) y pinzote) suministrados en tres dosis (1, 2 y 3%), en las propiedades químicas y microbiológicas del suelo y en el crecimiento del portainjerto Citrange troyer, en invernadero. Se utilizó un diseño completamente al azar con 14 tratamientos y seis repeticiones cada uno, incluyendo dos testigos (absoluto y fertilizado). Mediante diluciones seriadas en medios específicos se cuantificó Azospirillum, Azotobacter, y bacterias solubilizadoras de fosfatos y de potasio. Los hongos micorrízicos arbusculares fueron evaluados según la técnica de clareo y tinción con azul tripano. El pH del suelo se incrementó 0.9 unidades al agregar 1% de cachaza-2; mientras que el carbono orgánico se elevó 0.7% con el estiércol de gallina al 1%. Las bacterias Azospirillum, Azotobacter y solubilizadoras de fosfatos, se incrementaron en los tratamientos suministrados con cachaza-1 1% y estiércol de gallina 1%. La cachaza-1 2%, indujo mayor colonización micorrízica y mayor crecimiento de la planta. Ocho de los doce tratamientos con fertilizantes orgánicos utilizados, modif icaron positivamente las propiedades químicas y microbiológicas del suelo, dando como resultado un mejor crecimiento de Citrange troyer comparado con los testigos.

Mexico has more than 40 years of researching, investing, and obtaining electric power through wind energy. Within the country, there are highly windy areas, such as the Isthmus of Tehuantepec or the state of Tamaulipas, and there are about 2500 MW installed and 70,000 MW tested, all onshore. There are still no offshore wind farms in Mexico, despite having two main coasts, the East and the West, with the Gulf of Mexico and the Pacific Ocean, respectively. Although the Mexican coastal states of the Gulf of Mexico are Tamaulipas, Veracruz, Tabasco, Campeche, and Yucatán, this work focuses on the study and feasibility of offshore wind energy use on the coasts of the states of Tabasco, Campeche, and Yucatán. This is because of the availability of data in that region; however, sustainability criteria that can be used in other regions are also presented. MERRA-2 and ERA5 data were used employing WAsP and Windographer software. It was found that the capacity factor in the area of Tabasco, Campeche, and Yucatán is 32%, 37%, and 46%. It can be noted that, in the WF100% scenario, each of the wind farms could contribute more than 35% of the region’s electricity consumption; those of Campeche and Yucatán stand out with contributions of more than 70%.

In this study were examined chemical, microbiological, and enzymatic changes at different depths of the soil and rhizosphere, produced by the burning of a commercial sugarcane crop in tropical areas of Mexico. Samples of silty loamy soil and rhizosphere were collected at three times in the sugarcane production cycle: before burning (BB), after first burning (AFB), and after second burnings (ASB), with a general interval of 15 days between the first and the third collection date. Soil organic matter (SOM), soil organic carbon (SOC), total nitrogen (Nt), phosphorus available (Pav), pH, and the C/N ratio were determined in soil and rhizosphere, as well as the enzymatic activities of phosphatase and urease. Furthermore, microbial respiration, microbial biomass, and nitrogen-fixing bacteria (NFB) and phosphate solubilizing bacteria (PSB) densities were monitored during 84 days. The Pav and the pH increased significantly in soil samples affected by the second burning of the stubbles, but SOM, SOC, Nt, the C/N ratio, phosphatase, and urease activities decreased as a result of the first and second burnings. This decrease was more pronounced in non-rhizospheric soil. The densities of NFB and PSB increased with the burning, as well as microbial respiration. All the variables evaluated recorded higher values in the soil surface layer.

An experiment was performed for 240 days to evaluate the oil removal through natural attenuation (NA) and phytoremediation (PH) combined with surfactant (SF), in soil up to 76,585 mg kg−1 of total ...

Plants establish symbiosis with arbuscular mycorrhizal fungi (AMFs) for nutrient exchange and also for tolerance to contaminants. During February 2019, soil and rhizosphere samples of Laguncularia racemosa (Lr) and Avicennia germinans (Ag) were collected on 4.15 hectares of a mangrove forest established in Histosol affected since 1967 by chronic oil spill in southeastern Mexico. The site was divided into four zones based on the amounts of total hydrocarbons of weathered petroleum (THWPs) accumulated in the soil for half a century. The abundance of intraradical propagules and the colonization structure of the AMFs in the roots of the two mangrove species were compared. The density of phosphate-solubilizing bacteria (PSBs) in soil and rhizosphere samples was also evaluated. The degraded oil stimulated the amount of PSBs in Lr but not in Ag. AMF biodiversity was lower in the Ag root; however, spore abundance was higher. We found abundant spores of Glomus claroideum and Diversispora aurantium in tertiary and quaternary roots of the Ag in soils contaminated with 48462 mg of THWPs. This study provides evidence of the presence and abundance of intraradical propagules in different types of roots, which may be an alternative that contributes to the understanding of oil dissipation and in future applications for the restoration of degraded ecosystems.

Resumen La evaluación del impacto del petróleo en la interacción suelo-raíz de la planta de mangle blanco, Laguncularia racemosa, es básica para identificar los cambios en la actividad microbiana y en el potencial biotecnológico para la remediación de histosoles contaminados. El objetivo de la investigación fue evaluar la distribución espacial de los hidrocarburos totales del petróleo (HTP) en el suelo orgánico, la densidad poblacional de bacterias promotoras del crecimiento vegetal, así como la respiración microbiana en el rizoplano (RI) en la rizósfera (RZ) y en suelo no rizosférico (SNR) de L. racemosa. Una superficie de 8 000 m2 de un histosol afectado desde 1967 y 1968 se evaluó por derrame crónico de petróleo y lodos de perforación provenientes del pozo petrolero La Venta 248. Se seleccionaron 15 árboles de L. racemosa y se extrajeron muestras del RI, RZ y SNR. Los HTP se extrajeron en equipo soxhlet con diclorometano durante ocho horas y se cuantificaron por gravimetría. La cantidad promedio extraída de HTP permitió la diferenciación de cuatro suelos (S) en el área evaluada, con valor promedio para el S1 de 1 797 mg kg-1 (no contaminado para la normativa mexicana) y tres suelos contaminados: S2 con 3 294, S3: 5 249 y S4: 10 389 mg kg-1. Los resultados evidencian diferencias estadísticas (Duncan, P ≤ 0.05) entre medias de las variables evaluadas. La mayor acumulación de HTP fue 22 962 mg kg-1, se extrajo del SNR en el S4. Las mayores densidades de bacterias fijadoras de N, solubilizadoras de P, Azospirillum y Azotobacter fueron bioestimuladas por la presencia de niveles altos de HTP en el suelo, sin embargo la respiración microbiana fue inhibida. Los resultados sugieren que L. racemosa es sostenible en suelos con petróleo intemperizado, y es un bioestimulador de la actividad microbiana para la atenuación natural. Abstract The evaluation of the impact of oil on the soil-root interaction of the white mangrove plant, Laguncularia racemosa is essential to identify changes in microbial activity and biotechnological potential for remediation contaminated histosols. The objective was to evaluate the spatial distribution of total petroleum hydrocarbons (THP) in organic soil, the population density of plant growth promoting bacteria, also in microbial respiration in the rhizoplane (RI), in the rhizosphere (RZ) and in non-rhizospheric soil (NRS) of L. racemosa. An area of 8 000 m2 of an affected histosol was evaluated, during 1967 and 1968, by chronic oil spill and drilling mud from the La Venta 248 oil well. Fifteen trees of this species were selected to obtain samples of the RI, RZ and NRS. The TPH were extracted in soxhlet with dichloromethane for eight hours and quantified by gravimetry. The average amount extracted from TPH allowed the differentiation of four soils (S) from the evaluated area, the average values were for S1: 1 797 mg kg-1 (not contaminated for Mexican regulations) and three contaminated soils, the values are S2: 3 294, S3: 5 249, and S4: 10 389 mg kg-1. The results show statistical differences (Duncan, P ≤ 0.05) between means of the evaluated variables. The greatest accumulation of TPH was 22 962 mg kg-1, it was extracted from the NRS in S4. The highest densities of N-fixing bacteria, P solubilizers, Azospirillum and Azotobacter were biostimulated by the presence of high levels of THP in the soil, however microbial respiration was inhibited. The results suggest that L. racemosa is sustainable in soils with weathering oil, and is a biostimulator of microbial activity for natural attenuation.

Se evaluaron los efectos toxicos que produce un suelo contaminado con petroleo fresco sobre plantas de Phaseolus vulgaris . Para ello se genero un indice absoluto de fitotoxicidad que integra siete parametros, medidos a traves de indices relativos de fitotoxicidad para las variables: altura, longitud radical, numero de nodulos y biomasa seca (foliar, radical, del fruto y total). Asimismo, se calcularon los coeficientes de determinacion (R 2 ). El bioensayo se realizo bajo condiciones de tunel de plastico y se evaluo los efectos toxicos del petroleo en plantas de frijol negro ( P. vulgaris L.) al cabo de 100 dias. Se establecio un diseno experimental de bloques al azar en condiciones semicontroladas, con seis tratamientos con tres repeticiones por tratamiento. Las concentraciones de hidrocarburos fueron: 1500, 3000, 4500, 6000, 7500 y 9000 mg/kg de hidrocarburos totales del petroleo (HTP) y un tratamiento testigo (0 mg/kg).Al dia 100, el detrimento fisiologico [emergencia (R 2 = 0.89; b = -3.427); altura(R 2 = 0.84; b = -0.0029); longitud radical (R 2 = 0.62; b = -0.001); numero de nodulos (R 2 = 0.68; b = -0.0092) y biomasa total (R 2 = 0.77; b = -0.0014)] de las plantas mostro una correlacion negativa con la concentracion de los HTP en el suelo, con diferencias entre los tratamientos (Tukey p≤ 0.05). Al dia 68 del ensayo se observo marchitez de las plantas a concentraciones mayores de 3000 mg/kg HTP.

The oil industry has generated chronic spills and its accumulation in the mangrove forest located on the southeast coast of Mexico. The evaluation of the impact of oil on the soil-root interaction of Languncularia racemosa (Lr) is basic to determine the changes in microbial activity and its biotechnological potential for land remediation. Lr is a tree that grows in these areas contaminated with weathered oil. The objective of this study was to evaluate the spatial distribution in soil of total petroleum hydrocarbons (TPH), the population of plant growth promoting bacteria, microbial respiration in the rhizoplane (RI), rhizosphere (RZ) and non-rhizospheric soil. (SNR) of Lr. For this study, an area of ​​8,000 m2 of a Histosol affected by chronic oil spill and drilling mud from the La Venta 248 oil well was used. Fifteen Lr trees were selected and samples were taken from the RI (secondary roots), from the RZ (secondary and tertiary roots with adhered soil) and SNR (organic matter). The results show differences in the amount of HTP accumulated in the organic soil. The spatial distribution of the HTP defined four study floor (S): S1: 1797, S2: 3294, S3: 5249, and S4: 10389 mg kg-1. The PHT were higher in RI of S1 and 2, but in RZ and SNR in S2 and 3. In RI of Soil 4 the population of N-fixing and P-solubilizing bacteria were stimulated in greater quantity, but Azotobacter was inhibited and Azospirillum. For the RZ of Lr Azospirillum it was favored but in the soil 2 and 4. The microbial respiration at 7, 14, 21, 42 and 63 days was stimulated by the IR followed by the RZ in the four evaluated soils, however the respiration microbial was negatively affected by oil in the RI, RZ and SNR. The results suggest that Lr is sustainable in soils with hydrocarbon contamination, and is a biostimulator of microbial activity that can be used for the natural attenuation of hydrocarbons, with a high population of N-fixing bacteria and solubilizers of P in RI with 10389 mg kg-1 of HTP derived from weathered petroleum. However, soils containing HTP higher than 4158 mg kg-1 in RI, RZ and SNR require previous treatment to remove the oil and put it in contact with the RZ of the white mangrove. La evaluación del impacto del petróleo en la interacción suelo-raíz de la planta de mangle blanco, Laguncularia racemosa, es básica para identificar los cambios en la actividad microbiana y en el potencial biotecnológico para la remediación de histosoles contaminados. El objetivo de la investigación fue evaluar la distribución espacial de los hidrocarburos totales del petróleo (HTP) en el suelo orgánico, la densidad poblacional de bacterias promotoras del crecimiento vegetal, así como la respiración microbiana en el rizoplano (RI) en la rizósfera (RZ) y en suelo no rizosférico (SNR) de L. racemosa. Una superficie de 8 000 m2 de un histosol afectado desde 1967 y 1968 se evaluó por derrame crónico de petróleo y lodos de perforación provenientes del pozo petrolero La Venta 248. Se seleccionaron 15 árboles de L. racemosa y se extrajeron muestras del RI, RZ y SNR. Los HTP se extrajeron en equipo soxhlet con diclorometano durante ocho horas y se cuantificaron por gravimetría. La cantidad promedio extraída de HTP permitió la diferenciación de cuatro suelos (S) en el área evaluada, con valor promedio para el S1 de 1 797 mg kg-1 (no contaminado para la normativa mexicana) y tres suelos contaminados: S2 con 3 294, S3: 5 249 y S4: 10 389 mg kg-1. Los resultados evidencian diferencias estadísticas (Duncan, P ≤ 0.05) entre medias de las variables evaluadas. La mayor acumulación de HTP fue 22 962 mg kg-1, se extrajo del SNR en el S4. Las mayores densidades de bacterias fijadoras de N, solubilizadoras de P, Azospirillum y Azotobacter fueron bioestimuladas por la presencia de niveles altos de HTP en el suelo, sin embargo la respiración microbiana fue inhibida. Los resultados sugieren que L. racemosa es sostenible en suelos con petróleo intemperizado, y es un bioestimulador de la actividad microbiana para la atenuación natural. n el RZ del mangle blanco.

This study evaluated the effect of crude oil on the intraradical structures and morphospecies of arbuscular mycorrhizal fungi (AMF) and on the aerial and root dry matter of the grass Leersia hexandra Swartz in order to propose indicators of toxicity. An experiment was conducted in a microtunnel for 180 days. The concentrations (g kg−1) of crude oil in the Gleysol were 0.693 (control), 3, 10, 30, 60, 90, 120, 150, and 180. The growth of intraradical hyphae, arbuscules, vesicles, and spores in soil was stimulated by crude oil concentrations of 3, 10, 30 and 60 g, but concentrations of 90, 120, 150, and 180 g kg−1 inhibited it. Eight morphospecies of AMF were identified. The number of spores of Rhizophagus fasciculatus, Rhizophagus intraradices, Funneliformis geosporum, Diversispora eburnea, and Ambispora gerdemannii showed sensitivity to the concentration of crude oil (index values were lower than one). The number of spores of Diversispora sp. was stimulated by exposure to crude oil, with non-toxic values for the eight concentrations. The index based on the aerial dry matter of L. hexandra showed toxicity values lower than one with crude oil concentrations of 60, 90, 120, 150, and 180 g kg−1, but the root dry matter showed non-toxic values with the eight concentrations. We suggest using the number of spores and morphospecies as an index of toxicity of crude oil and recommend using Diversispora sp. and L. hexandra for the phytoremediation of Gleysol contaminated with crude oil in the Mexican humid tropics.

The aim of this study was to evaluate the spatial distribution of total petroleum hydrocarbons (TPH) in rhizoplane and non-rhizosphere of Leersia hexandra, known as Japanese grass, the effect of oil on the aerial biomass of L. hexandra, the population of plant growth-regulating bacteria, and microbial respiration in rhizosphere and non-rhizospheric soil. Samples of rhizosphere and soil were collected at 14 points across a surface of 2.3 ha, layer 1 (0–15-cm depth), layer 2 (15–30 cm), and layer 3 (30–70 cm), to measure TPH (mg kg−1). The spatial distribution of TPH defined four study zones (Z): Z1: 1393, Z2: 3455, Z3: 5574, and Z4: 7544. TPH were higher in underlying layers in the four zones. Zone 2 produced the largest amount of aerial biomass; oil induced hormesis in the grass, but inhibited it at doses ≥5574. For the rhizosphere of L. hexandra, it was cut with a sterilized knife, stimulated the population of N-fixing and phosphorus solubilizing, heterotrophic bacteria, as well as microbial respiration (day 1, 14, 21, 42, and 63 after incubation) in the four zones. The population of the three groups of bacteria was more stimulated by weathered oil in rhizosphere soil, compared to non-rhizosphere soil and with control treatment, suggesting that the rhizosphere system of L. hexandra has the potential to bioestimulate beneficial microbial activity in unpolluted and polluted areas compared to non-rhizosphere soil. We recommend the use of L. hexandra to recover soils degraded by weathered oil in farms located in the Mexican humid tropics.

An experiment was conducted in field for three years to assess the sustainability of aquatic plants Leersia hexandra, Cyperus articulatus, and Eleocharis palustris for use in the removal of total hydrocarbons of weathered oil in four areas contaminated with 60916-119373 mg/kg of hydrocarbons. The variables evaluated were coverage of plant, dry matter, density of plant growth-promoting rhizobacteria, and the removal of total weathered oil. The variables showed statistical differences (p = 0.05) due to the effects of time and the amount of oil in the soil. The three aquatic plants survived on the farm during the 36-month evaluation. The grass L. hexandra yielded the greatest coverage of plant but was inhibited by the toxicity of the oil, which, in contrast, stimulated the coverage of C. articulatus. The rhizosphere of L. hexandra in control soil was more densely colonized by N-fixing bacteria, while the density of phosphate and potassium solubilizing rhizobacteria was stimulated by exposure to oil. C. articulatus coverage showed positive relationship with the removal of weathered oil; positive effect between rhizosphere and L. hexandra grass coverage was also identified. These results contributed to the removal of weathered oil in Gleysols flooded and affected by chronic discharges of crude oil.

The aims of our study were to compare the effectiveness of poultry manure (PM) and banana waste (BW), with regard to their use as inoculant carriers of a bacterial consortium constituted by strains of Azospirillum, Azotobacter and P-solubiliser bacteria and to establish the most efficient dose of biofertilizer for a soil cultivated with banana (Musa paradisiaca AAA Simmonds), with respect to improving plant performance and soil physical and microbiological properties. Six months after planting, plant growth had increased with increase in dose of the biofertilizers applied. The biofertilizer prepared on BW enhanced the density of P-solubiliser bacteria, the concentrations of available P and foliar P to a greater extent than with the biofertilizer prepared on PM. The increases produced by the biofertilizer prepared on PM for the soil aggregate stability, enzymatic activities and the labile carbon fractions were highly correlated to the dose applied. Both biofertilizers can be considered potentially useful as inoculant carriers of PGPR but the usefulness of BW appears to be restricted to moderate doses of application (� 3%). 2008 Elsevier Ltd. All rights reserved. The banana (Musa paradisiaca AAA Simmonds) c.v. ‘Dwarf Cavendish’ is an important food crop in tropical areas of Mexico, with a cultivated area of 76,313 ha and an annual production of 2,196,155 Tm (SIAP-SAGARPA, 2006). In particular, about 19% of surface cultivated with banana is located in the state of Tabasco (SE Mexico). The system production is based on intensive use of inorganic fertilizers and pesticides that yields 7–70 Mg ha � 1 of banana

Compactación, Densidad aparente, Humedad, Infiltración básica, Retención de agua, Textura.

Los estudios toxicológicos permiten identificar las especies vegetales más sensibles a concentraciones bajas de contaminantes en el suelo. Las leguminosas son plantas con órganos y respuesta fisiológica sensibles a concentraciones bajas de petróleo en el suelo. El objetivo del presente estudio fue evaluar y explicar la respuesta en crecimiento, biomasa total, número de nódulos y en ausencia/ presencia de leghemoglobina en los nódulos de cuatro leguminosas a diferentes concentraciones de petróleos nuevo (recién extraído) o intemperizado (expuesto al ambiente por más de 20 años). Se realizaron dos ensayos de fitotoxicidad en invernadero. El primero con plantas de chipilín silvestre (Crotalaria sp) durante 120d con arreglo factorial 1×5 y diseño al azar con cuatro repeticiones por tratamiento, con concentraciones de petróleo de 150 (suelo testigo), 7500, 25000, 50000 (nuevo) y 79457 (intemperizado) mg·kg-1 de hidrocarburos totales del petróleo (HTP), base seca. El segundo ensayo fue durante 150d, con dormilona (Mimosa sp), guaje (Leucaena sp) y zarza (Mimosa pigra) en un arreglo factorial 3×5 en un diseño al azar con cuatro repeticiones, y concentraciones de 150, 50000, 79457, 100000 y 150000 mg·kg-1 de HTP, base seca. Hubo diferencias estadísticas significativas en todas las variables evaluadas, que se asociaron negativamente con la presencia de petróleo en el suelo. Chipilín silvestre fue la planta más sensible a la exposición al petróleo y evidenció mejor su fitotoxicidad, por lo que podría ser utilizada como especie fitoindicadora de suelos contaminados con petróleo. El número de nódulos con leghemoglobina fue el indicador más sensible para medir el efecto fitotóxico del petróleo. Toxicological studies enable to identify those plants with the highest sensibility to low concentrations of soil pollutants. Leguminous plants have extremely sensible organs and physiological responses to low concentrations of oil in the soil. The object of this study was to assess and explain the response in terms of growth, total biomass, number of nodules and presence/absence of leghaemoglobin in the nodules of four different leguminous plants at four different concentrations of oil under two conditions: new oil, recently extracted, or weathered oil, exposed to the environment for >20 years. Two phytotoxicity assays were carried out under greenhouse conditions. The first involved «wild chipilín» plants (Crotalaria sp) for 120 days with a 1×5 factorial arrangement and a random design with four replicates per treatment, testing oil concentrations (in mg·kg-1 of total petroleum hydrocarbons (TPH), dry weight) of 150 (control soil), 7500, 25000, 50000 (new oil) and 79457 (weathered oil). The second assay lasted 150 days, testing plants of "dormilona» (Mimosa sp), «guaje» (Leucaena sp) and «zarza» (Mimosa pigra), in a 3×5 factorial arrangement, at random with four replicates. The concentrations tested were 150, 50000, 79457, 100000 and 150000 mg·kg-1 TPH, dry weight. Statistically significant differences were found in all variables, being negatively associated to the presence of oil in soil. Wild chipilín was the most sensitive species to oil exposure, better showing its phytotoxicity, so that it could be used as a phytoindicative species of oil-polluted soil. The number of nodules containing leghaemoglobin was the most sensitive indicator of oil’s phytotoxic effect. Os estudos toxicológicos permitem identificar as espécies vegetais mais sensíveis a concentrações baixas de contaminantes no solo. As leguminosas são plantas com órgãos e resposta fisiológica; sensíveis a concentrações baixas de petróleo no solo. O objetivo do presente estudo foi avaliar e explicar a resposta em crescimento, biomassa total, número de nódulos e na ausência/ presença de leghemoglobina nos nódulos de quatro leguminosas a diferentes concentrações de petróleo novo (recém extraído) ou intemperizado (exposto ao ambiente por mais de 20 anos). Realizaram-se dois ensaios de fitotoxicidade em invernadeiro. O primeiro com plantas de "guizo-de-cascavel" ou "xiquexique" (Crotalaria sp) durante 120 dias com arranjo fatorial 1×5 e desenho ao acaso com quatro repetições por tratamento, com concentrações de petróleo de 150 (só testemunha), 7.500, 25.000, 50.000 (novo) e 79.457 (intemperizado) mg·kg-1 de hidrocarbonetos totais do petróleo (HTP), base seca. O segundo ensaio foi durante 150 dias, com Jurema de Imbira (Mimosa sp), leucena (Leucaena sp) e "malícia-de-boi" ou "Jiquiri Grande" (Mimosa pigra) num arranjo fatorial 3×5 em um desenho ao acaso com quatro repetições, e concentrações de 150, 50.000, 79.457, 100.000 e 150.000 mg·kg-1 de HTP, base seca. Houve diferenças estatísticas significativas em todas as variáveis avaliadas, que se associaram negativamente com a presença de petróleo no solo. «Guizo-de-cascavel» ou «xiquexique» foi a planta mais sensível à exposição ao petróleo e evidenciou melhor sua fitotoxicidade, pelo que poderia ser utilizada como espécie fitoindicadora de solos contaminados com petróleo. O número de nódulos com leghemoglobina foi o indicador mais sensível para medir o efeito fitotóxico do petróleo.

El estudio del comportamiento de plantas en suelos contaminados con petróleo permite identificar y seleccionar especies fitoindicadoras de tal contaminación. Se estudió el efecto del petróleo en el suelo sobre la diversidad, cobertura y productividad en una pradera en el sureste de México. Se evaluaron diferentes concentraciones de petróleo nuevo e intemperizado en la germinación, crecimiento, biomasa aérea, radical y total, y número de nódulos. La pradera se dividió en cuatro áreas según la concentración de hidrocarburos totales de petróleo (HTP): 150, 2791, 9035 y 79457mg·kg-1. La mayor diversidad vegetal se encontró en los dos suelos más contaminados pero la producción de biomasa se redujo hasta 50% respecto al suelo con menos HTP. Se realizaron tres experimentos secuenciales en plántulas durante 32 días de exposición al petróleo, y en plantas durante 150 días de exposición, en arreglo factorial y diseño al azar, con las especies Echinochloa polystachya, Brachiaria mutica, Cyperus articulatus, Cyperus sp. y Mimosa pigra. Se prepararon tres concentraciones (50000, 100000 y 150000 mg·kg-1) para compararlos con el petróleo intemperizado (79457mg·kg-1). Se aplicó el protocolo OCDE Nº208 para evaluar efecto tóxico en plántulas y para plantas se diseñó un protocolo. Se evaluaron germinación, altura, longitud de raíz, biomasa y número de nódulos. Hubo diferencias significativas en todas las variables en plántulas y plantas de las cinco especies. La germinación se asoció positivamente con las mayores concentraciones de petróleo intemperizado, pero se redujeron crecimiento, longitud de la raíz, biomasa y número de nódulos en plántulas. En plantas todas las variables fueron reducidas. Las especies más sensibles, mejores fitoindicadoras de niveles tóxicos, fueron E. polystachya y B. mutica en plántulas, y M. pigra en plantas. The study of plant behavior in petroleum contaminated soils allows the identification and selection of oil pollution indicator species. The effect of soil petroleum on the diversity, canopy and productivity of a prairie in Southeastern Mexico was studied. Different and tempered petroleum concentrations were evaluated on the germination, growth, aerial, root and total biomasses, and number of nodules. The praire was divided in four areas according to the total petroleum hydrocarbons (THP) concentration: 150, 2791, 9035 and 79457mg·kg-1. The largest diversity was found in the two most contaminated soils but biomass production was 50% lower than in the soil with less THP. Three sequential experiments were carried out, on sprouts for a 32 day exposure to oil, and on plants for a 150 day exposure, using a random factorial analysis and the species Echinochloa polystachya, Brachiaria mutica, Cyperus articulatus, Cyperus sp. and Mimosa pigra. Three concentrations (50000, 100000 y 150000 mg·kg-1) were prepared for comparison with tempered petroleum (79457mg·kg-1). OECD Protocol Nº208 was applied to evaluate the toxic effects on sprouts and a protocol was designed for plants. Germination, height, root length, biomass and number of nodules were evaluated. Significant differences were found in all variables in sprouts and plants of the five species. Germination was positively associated with the largest tempered petroleum concentrations but growth, root length, biomass and number of nodules were reduced in sprouts. In plants all the variables were reduced. The most sensitive species, best phytoindicators of toxic levels were E. polystachya and B. mutica in sprouts and M. pigra in plants O estudo do comportamento de plantas em solos contaminados com petróleo permite identificar e selecionar espécies fito-indicadoras de tal contaminação. Estudou-se o efeito, do petróleo no solo, sobre a diversidade, cobertura e produtividade em um prado no sudeste do México. Avaliaram-se diferentes concentrações de petróleo novo e intemperizado na germinação, crescimento, biomassa aérea, radical e total, e o número de nódulos. O prado dividiu-se em quatro áreas segundo a concentração de hidrocarbonetos totais de petróleo (HTP): 150, 2791, 9035 e 79457mg·kg-1. A maior diversidade vegetal encontrou-se nos dois solos mais contaminados mas, a produção de biomassa reduziu-se até 50% com respeito ao solo com menos HTP. Realizaram-se três experimentos seqüenciais em plântulas durante 32 dias de exposição ao petróleo, e em plantas durante 150 dias de exposição, em arranjo fatorial e modelo ao azar, com as espécies Echinochloa polystachya, Brachiaria mutica, Cyperus articulatus, Cyperus sp. e Mimosa pigra. Prepararam-se três concentrações (50000, 100000 y 150000 mg·kg-1) para comparar com o petróleo intemperizado (79457mg·kg-1). Aplicou-se o protocolo OCDE Nº208 para avaliar efeito tóxico em plântulas e para plantas se desenhou um protocolo. Avaliaram-se germinação, altura, longitude da raiz, biomassa e número de nódulos. Houve diferenças significativas em todas as variáveis em plântulas e plantas das cinco espécies. A germinação se associou positivamente com as maiores concentrações de petróleo intemperizado, mas se reduziram crescimento, longitude da raiz, biomassa e número de nódulos em plântulas. Em plantas, todas as variáveis foram reduzidas. As espécies mais sensíveis, melhores fito-indicadoras de níveis tóxicos, foram E. polystachya e B. mutica em plântulas, e M. pigra em plantas.