Hydrocarbon contaminated soil is a global problem. In Mexico, the regulations for environmental protection do not include any bioindicators to evaluate toxic effects in microorganisms and plants caused by hydrocarbons. The jamaica plant (Hibiscus sabdariffa L.) has a percentage of germination that is greater than 90%, and nascence occurs between 2 to 3 days. Thus, the objective was to verify whether the jamaica plant would be a viable bioindicator of toxicity in soil contaminated by hydrocarbons. In the toxicity bioassay, three hydrocarbon concentrations were tested: 895 ppm (T1), 447 ppm (T2), 223 ppm (T3) and a control without hydrocarbon (C), for two soils at the coast of Oaxaca, México (Bajos de Coyula and Barra de la Cruz). The germination index (GI) that integrates the relative percentage of germination (RPG) and the relative root growth (RRG) was determined. The following relationship was obtained: lower value at higher hydrocarbon concentration, in the indices that were tested. Inhibition in seedling height was lower than in root growth; while in the root growth up to 73.4% was inhibited, in the seedling height only 6% (T3) and 48% (T1) were inhibited. GI mean in Barra de la Cruz (43.7) was 1.1 times greater compared to Bajos de Coyula (39.3). Partial reduction of oxygen and lack of moisture in the soil matrix could be the possible causes of the negative effect on germination due to hydrocarbon. GI of the jamaica, was negatively affected by the hydrocarbon in soil, but, germination was not completely inhibited. Based on these observations, we suggest that the jamaica plant (Hibiscus sabdariffa L.) can be used as a bioindicator of toxicity in hydrocarbon contaminated soil.
Hibiscus sabdariffa L.; bioindicator; toxicity; hydrocarbon; hormesis.
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