Soil Heavy Metal Absorption Potential of Azolla pinnata and Lemna gibba with Arbuscular Mycorrhizal Fungi in Rice (Oryza sativa L.) Farming

Abstract

This study assessed the potential uptake of soil-contaminated heavy metals by Azolla pinnata and Lemna gibba in combination with and without arbuscular mycorrhizal fungi (AMF) in traditional and improved rice varieties. Total levels of cadmium (Cd), lead (Pb), mercury (Hg), and arsenic (As) in soil, rice roots, shoots, grains, A. pinnata, and L. gibba were estimated using ICP-MS. The percentage colonization in AMF-inoculated and AMF-uninoculated rice varied from 1.13–30.67% and 1.33–5.42%, respectively. These findings suggested that AMF provide protection to rice plants against the combined toxicity of Cd, As, Pb, and Hg in rice field soil. The combined interaction of AMF, organic fertilizer, and A. pinnata decreased heavy metal accumulation in rice roots, shoots, and grains in both tested varieties. The intake and subsequent accumulation of Cd, As, Pb, and Hg in the rice grains differed significantly (p < 0.05) between the two rice varieties. Furthermore, it was revealed that the AMF-inoculated rice plants reduced the translocation of heavy metals from root to shoot. Therefore, it can be concluded that heavy metal absorption and accumulation in rice can be reduced by the application of AMF, organic fertilizer, and A. pinnata together in rice farming.