Abstract
Introduction: Plants and microorganisms have been used as bioindicators to evaluate the toxicity of hydrocarbons in soils. Objective: This study evaluates the toxicity of a chronically-contaminated Gleysol with several concentrations of weathered petroleum hydrocarbons (WPH), collected from La Venta, Tabasco (Mexico), on the growth of Clitoria ternatea and the phytoxicity attenuation due to inoculation of emulsifying bacteria. Methods: Soils with 50 and 150 g WPH kg-1, and control soil with 0.15 g WPH kg-1 (biogenic origin) were utilized, as well as the inoculation of six emulsifying bacteria and their combination (consortium). The WPH-phytotoxicity was evaluated by considering plant height, dry biomass production (root, shoot, and total), leaf area, specific leaf area, and the efficiency of photosystem II (EPSII), after 30 days. Results: WPH did not affect plant height, but soil with 50 g WPH kg-1 diminished root and total dry weight, and leaf area, when compared to both control soil and soil with 150 g WPH kg-1. The strain Sml (Stenotrophomonas maltophilia C10S1) significantly increased shoot and total dry weight, while the strain Ro (Raoultella ornithinolytica C5S3) produced higher specific leaf area relative to uninoculated plants. In control soil, the bacterial consortium stimulated plant height. The strains Sm (Serratia marcescens C11S1) and Sm2 (S. marcescens C7S3) improved plant height and specific leaf area when compared to uninoculated plants in soil with 50 g WPH kg-1. In soil with 150 g WPH kg-1, strains Spa (Stenotrophomonas pavanii C5S3F) and Cfr (Citrobacter freundii C4S3) enhanced root and shoot dry weight, respectively. The EPSII was unaffected by soil contamination. Emulsifying bacteria reduced the phytotoxic effects of WP, but depending on the content of WPH in soils. Conclusions: Soil with 50 g WPH kg-1 showed the greatest phytotoxic effects on plant growth. Bacterial inoculation favored growth, biomass production and leaf area in soil with 150 g WPH kg-1. The EPSII was not affected by WPH in soils.
Highlights
A nivel mundial el petróleo es una de las fuentes de energía más importantes para la economía
Las especies utilizadas en la fitorremediación incluyen gramíneas y leguminosas (Khan, Afzal, Iqbal, & Khan, 2013; Khan, Biswas, Smith, Naidu, & Megharaj, 2018); aunque las leguminosas son más susceptibles que las gramíneas a sufrir daños severos por exposición a los hidrocarburos totales del petróleo intemperizados (HTPI) en el suelo, por lo que pueden ser utilizadas como indicadoras de toxicidad inducida por estos compuestos (Khan et al, 2013; Morales-Guzmán et al, 2017)
Las bacterias productoras de surfactantes mejoran la dispersión y favorecen la remoción de los compuestos del petróleo, mediante el proceso de emulsificación permitiendo que sean utilizados como co-sustrato, y fuente de energía para satisfacer el metabolismo microbiano e incrementar la degradación de los hidrocarburos del petróleo, favoreciendo el crecimiento de las plantas (Morales-Guzmán et al, 2017; Reddy, Karegoudar, & Nayak, 2018; Cecotti, Coppotelli, Mora, Viera, & Morelli, 2018)
Summary
A nivel mundial el petróleo es una de las fuentes de energía más importantes para la economía. El objetivo de la presente investigación fue evaluar la fitotoxicidad en el crecimiento de C. ternatea, y el efecto de la inoculación de bacterias emulsificantes en la atenuación de la toxicidad inducida por un Gleysol contaminado de origen, con diferentes concentraciones de petróleo intemperizado, recolectado en La Venta, Tabasco (México).
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