Phytoremediation of cadmium improved with the high production of endogenous phenolics and free proline contents in Parthenium hysterophorus plant treated exogenously with plant growth regulator and chelating agent

Pot experiments were conducted to evaluate the effects of gibberellic acid (GA(3)) and ethylenediaminetetraacetic acid (EDTA) on growth parameters, cadmium (Cd) phytoextraction, total phenolics, free proline and chlorophyll content of Parthenium hysterophorus plant grown in Cd-contaminated (100 mg/kg) soil. GA(3) was applied as foliar spray (10(-2), 10(-4) and 10(-6) M) while EDTA (40 mg/kg soil) was added to soil as single and in split doses. Results showed decrease in growth parameters due to Cd stress but P. hysterophorus plant demonstrated Cd hyperaccumulator potential based on bioconcentration factor (BCF). Lower concentration of GA(3) (10(-6) M) showed highest significant increase in the growth parameters while Cd concentration, accumulation (1.97 +/- 0.11 mg/DBM) and bioconcentration (9.75 +/- 0.34) was significantly higher in the treatment T11 (GA(3) 10(-2) + split doses of EDTA). Cadmium significantly increased the root free proline while total phenolic concentration was significantly high in all parts of the plant. Chlorophyll contents were significantly reduced by Cd. GA(3) showed significant increase in phenolic and chlorophyll contents in plant. Cadmium accumulation in plant tissues showed positive correlation with free proline (R (2) = 0.527, R (2) = 0.630) and total phenolics (R (2) = 0.554, R (2) = 0.723) in roots and leaves, respectively. Cd contents negatively correlated with biomass, chlorophyll and total water contents. Proline and phenolic contents showed positive correlation with dry biomass of plant. These findings suggest further investigation to study the role of endogenous phenolics and proline in heavy metal phytoremediation.