Phytoremediation by Leucaena leucocephala in Association with arbuscular endomycorrhiza and Rhizobium in soil polluted by Cr

摘要

Chromium (Cr) is a heavy metal with risk to human health, and a contaminant found in agricultural soil and industrial sites. Phytoremediation, which relies on phytoextraction of Cr by biological organisms, is an important alternative to costly physical and chemical methods of treating contaminated sites. The ability of microorganisms like Rhizobium and arbuscular endomycorrhizal fungi (Glomus spp.) to enhance Cr uptake and plant tolerance was tested with the leguminous plant, Leucaena leucocephala, from southern Mexico and Guatemala, that grows in a wide diversity of soils. It is capable of surviving frosts. This study showed that the initial amount of Cr added to the soil in a pot decreased gradually. This tendency was similar at both concentrationsrnevaluated (20 and 200 mg kg~(?1)). The pots were watered with a slight excess, thus creating the possibility of a lixiviation of the metal. However, this was rather small, so the decrease of the metals in the soil could be attributed mainly to the plant uptake. In this case the mycorrhizal fungi Glomus sp. Zac-19, and Glomus intraradices, as well as Rhizobium strains, helped to partially alleviate Cr toxicity as indicated by greater plant growth. A considerable Cr accumulation was shown in non-colonized plants with 200 mg·kg~(-1), total mycorrhizal colonization as well as its componentes, arbuscular, and vesicles were affected more than by 20 mg·kg~(-1) or 0 mg·kg~(-1) of Cr. In addition, the magnitude was reduced for N, P, K. content, plant height, number of branches, stem diameter, number of leaves, number of leaflets, length of leaves, width of leaves, length of root, root volume, dry weight of roots, leaf area, dry weight of leaves, dry weight of stem, number of nodules, dry weight of nodules, total percentage of colonization (TC), and Cu and Cr contents in the leaf and stem. The results will help to design strategies for using Leucaena leucocephala. Associated with arbuscular endomycorrhiza and Rhizobium in bioremediation of Cr accumulation.