Axonopus compressus (Sw.) Beauv.: A potential biomonitor for molybdenum in soil pollution

Phytoremediation is an emerging technology that utilizes plants to remediate contaminated environments. In this study, Axonopus compressus (Sw.) Beauv, a fast-growing and hardy groundcover with wide geographical distribution, was exposed to soil Mo treatments ranging from 100 to 1000 mg/kg under tropical greenhouse conditions for five weeks. Generally, Mo accumulation increased as the concentration of Mo in the soil increased. The species was found to accumulate about 4000 mg/kg of Mo without exhibiting severe physiological stress at 600 mg/kg of soil Mo. Maximum accumulation of 6000 mg/kg Mo was observed at the 1000 mg/kg soil Mo treatment, though with severe necrosis and eventual plant mortality. The physiological observations, Mo accumulation behavior, and a bioconcentration factor of about 1 indicated that A. compressus could be a potential biomonitor of Mo.