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

Abstract

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.