Possible adaptive growth responses of <i>Chromolaena odorata</i> during heavy metal remediation

Abstract

The changes in morphological and crude protein content of Chromolaena odorata to heavy metal-induced stress were investigated. This was with a view to providing information on the test plant adaptation potential during remediation of contaminated with . Stems of C. odorata were planted in soils treated with Cd (as CdCl) and Pb (as PbCl) at different concentrations of 6.67, 33.3 and 100 mg/kg respectively, singly and in combinations (Cd+Pb). After the exposure of C. odorata to heavy metals for 3 months, results showed that residual Pb concentration in soil was 4.31 mg/kg in the 6.66mg (Pb)/kg-polluted soil, compared to the control (0.7 mg/kg). Residual concentration of Cd in soil was 0.22 mg/kg in the soil originally polluted with 6.66 mg (Cd)/kg, compared to a residual concentration of 5.94 mg/kg in the 100 mg (Cd)/kg-polluted soil. Residual metal concentration after plant exposure was lower for Cd in Cd-polluted soil than for Pb in Pb-polluted soils suggesting better plant-assisted remediation of Cd than Pb. Total crude protein content of plants exposed to metals increased with increase in metal concentration in soil. The presence of metal in soil reduced plant height from 127 cm in the control to a range of vales from 93 – 117 cm in the plants exposed to metal contamination. However, at lower concentrations of the Cd in soil, plants showed improved root branching (117.00±11.31), compared to the control (62.35±5.63). Results of the study further show the capability of C. odorata for metal remediations and also possible morphological adaptation mechanisms of survival in metal-impacted soils.

Keywords: Heavy metals, bioremediation, crude protein, adaptation, Chromolaena odorata