Chromium and arsenic bioaccumulation and biomass potential of pink morning glory (Ipomoea carnea Jacq.).

Abstract

Soil contamination with heavy metals and metalloids is a global concern nowadays. Phytoremediation is an eco-friendly, cost-effective, and sustainable way of mitigating such contamination by utilizing the plants' ability to accumulate, sequester, and stabilize elements. Biomass-producing plants may outperform hyperaccumulators in terms of total elemental removal and offer more cost-effectiveness through their usable biomass. Ipomoea carnea is a wild plant in the Asian region. It is resilient, spreads rapidly in a wide range of soil conditions, and has a high potential for biomass feedstock. In this work, we have tested this plant species for its growth performance and accumulation characteristics of Cr and As. In a pot experiment, the plants could easily grow from rootless stem segments in 2 weeks when garden soils are treated with 100-500 ppm of Cr and 20-300 ppm of As. Plant growth reduction was little at the moderate level of these elements, with a significant accumulation of elements in 45 days. Within this time, in the stems and leaves, the Cr concentrations were found to be 49 and 39 ppm, respectively, when treated with 500 ppm of Cr, whereas the As concentrations were obtained as 83 and 28 ppm, respectively, for the treatment with 300 ppm of As. To estimate the biomass production potential, the plant was grown with a density of 80,000 per ha under normal field conditions (without metal stress). At the harvest, the plants consisted of 80% stems, 11% leaves, and 9% belowground portions on a dry weight basis. The dry weight of stems, leaves, and belowground parts was 31.3%, 17.9%, and 23.7%, respectively. Overall, the estimated biomass was 25.8 Mg/ha/year from three harvests. The ability to regrow from the basal part makes it useful for continuous sequestration of toxic elements over multiple harvests. Our results show that I. carnea could lower Cr and As from contaminated soils and potentially a phytoremediation candidate considering accumulation rate and high amount of usable biomass production.