Amendments for enhancing phytoextraction potential of marigold (Tagetes erecta L.) in heavy metal polluted soil: effects on crop growth, physiological and biochemical responses.

To enhance phytoextraction potential of marigold (Tagetes erecta L. var. Pusa Bahar), an attempt was made to increase the bioavailability of heavy-metals in a polluted-soil through organic amendments and microbial inoculant. The study evaluated the effectiveness of farmyard manure (FYM), green-manure (Sesbania sp.) and heavy-metal solubilizing bacteria (MSB: Bacillus aerius-WSB68) when applied in different combinations for enhancing the bioavailability of Ni and Zn in marigold grown on a polluted-soil. A greenhouse pot experiment was conducted to prove the hypothesis. Results indicated that FYM application at 3% w/w (T2) improved growth and flowering traits; whereas, the combined-application of FYM (at 3% w/w), Sesbania (at 30 g fresh leaf kg-1 soil) and MSB (T7) enhanced heavy-metal bio-availability, which resulted in stress-induced higher antioxidant-enzyme activities, carotenoid content, and other biochemical properties, relative water-content and membrane-stability index of test crop with respect to control. Plants in polluted-(control)-soil (T1) showed higher photosynthetic rate, stomatal conductance and transpiration rate due to lower heavy-metal bioavailability with respect to amended soils. Findings of the present study indicate that combined-application of FYM, green manure and MSB in metal polluted-soil could be effective in enhancing phytoextraction potential of the ornamental marigold without compromising its growth and aesthetic quality of flower.