Germination tolerance of legumes exposed to soil with As, Cd, Cr and Pb from La Escondida lagoon, Tamaulipas, Mexico

Abstract

Urban growth and industrial development in Reynosa, Tamaulipas, Mexico have contaminated the soil of the La Escondida lagoon with potentially toxic elements (PTE), such as As, Cd, Cr, and Pb. However, legumes such as Neltuma glandulosa, Parkinsonia aculeata, and Leucaena leucocephala are found within the lagoon and can be used as a preliminary tolerance test for phytoremediation. This study evaluated the germination tolerance of legumes exposed to the lagoon soil. Physical and chemical soil parameters (texture class, N, P, K, CIC, pH, and electrical conductivity) were quantified. Aqueous extracts were then prepared for germination (10 seeds were placed on absorbent paper in Petri dishes, and 13.5 mL of the extract was added). Germination percentage (GP), relative GPR, relative root length (RRL), and germination index (GI) were measured over one week. The physical and chemical parameters were analyzed using Tukey's test. Subsequently, the means of the germination variables were correlated via Manova, and finally, all study variables were correlated using principal component analysis (PCA). The results showed that N. glandulosa and P. aculeata, with a higher germination index (GI) (73.06\% and 100\%, respectively), are significantly different (P <= 0.05) from A. lebbeck and L. leucocephala in GPR, RRL, and GI. The PCA indicates that these same parameters have a 5.90\% contribution in N. glandulosa and P. aculeata compared to the latter two species. N. glandulosa and P. aculeata are tolerant to EPTs.