Inoculation of a metalophytic plant with arbuscular mycorrhizal fungi from lead contaminated soils

Abstract

The city of Córdoba is one of the most polluted cities in Argentina, with a large number of industrial plants located in urban and suburban areas. At 18 km from the capital of Córdoba is the town of Bouwer, considered one of the areas most affected by heavy metal contamination. An acid battery recycling factory dedicated to the recovery of lead (Pb) operated irregularly between 1984 and 2005. The smelter emitted Pb into the air and leaved a large amount of slag, used by neighbors to fill and level land. This caused numerous cases of Pb poisoning. Given the health risks and residence times of pollutants, it is necessary to apply remediation measures such as phytoremediation. For example the indigenous plant, B. pilosa, is a metalophytic plant species adapted to the climatic conditions and the soil of the area. The same behavior has been observed with native Arbuscular Mycorrhizal Fungi (AMF), which are important to be used as inoculants in remediation programs. Therefore, is important to select AMF species adapted to these contaminated sites. In the present work, the inoculation of B. pilosa seedlings with native AMF spores from Bouwer was evaluated. Seeds of B. pilosa collected in the field were sterilized and rinsed with sterile water. Seedlings were grown in hydroponic cultures enriched with Hoagland solution without phosphate. After 3 weeks, the seedlings were separated into 2 treatments: 1) added a Hoagland solution plus 1 mM Pb (NO3)2 and 2) added a Hoagland solution plus 1 mM NH4NO3. Thus, plants with Pb and without Pb were obtained to continue the experiment. After that, B. pilosa were inoculated with AMF (300-400 spores) from Bouwer: control site (Pb: 25 μg g-1) and a site with Pb (Pb: 7027 μg g-1). Each treatment had five repetitions and the plants were developed under controlled greenhouse conditions for 150 days. After that, the arbuscular mycorrhizal colonization was evaluated by roots staining, observed and counted under microscope. Arbuscular mycorrhizal fungi structures were observed in B. pilosa roots. Besides, a higher percentage of colonization (30%) was registered in plants with Pb and inoculated with AMF from the site with Pb compared to the rest of the treatments. This preliminary study show that AMF isolated from contaminated sites potentially increased the arbuscular mycorrhization in B. pilosa seedlings with Pb inside.