Assessment of leaf morphological characteristics, phenolics content and metal(loid)s concentrations in Calendula officinalis L. grown on fly ash amended soil

An experiment in pot culture was conducted to analyze the ameliorative impact of different doses of fly ash (FA) in soil on the plant growth performance, total phenolics and flavonoids, and elemental uptake in Calendula officinalis. To determine the growth status of Calendula officinalis, various concentrations of FA and soil [100% garden soil (T1), 20% FA+ 80% garden soil (T2), 40% FA+ 60% garden soil (T3), 60% FA+ 40% garden soil (T4), 80% FA+ 20% garden soil (T5), and 100% FA (T6)] were selected. The physico-chemical properties of FA and soil and elemental concentrations (Ca, Mg, Al, As, Co, Zn, Fe, Mn, and Ni) in all FA treatments were determined. The results showed that under low ratio of FA amendment to the soil (40% FA treatment), the plant growth performance was increased in comparison to plants grown in control (garden soil). However, at high FA doses in soil (60%, 80% and 100% FA treatments), these parameters tend to decrease. Fly ash at 40% concentration did not contain toxic concentrations of these elements such as Co, Zn, Fe, Mn, Ca, Mg, Al, As, and Ni, therefore, beneficial effects of fly ash in terms of improved growth and yield were evident. Furthermore, the leaves showed increasing trend of total phenolic and flavonoid content with increasing FA application up to 60% FA treatment. Therefore, this study showed that 40% FA treatment to the soil is suitable for the growth and yield of Calendula officinalis. Thus, this plant has the phytoremediation potential that can promote cleanup of FA polluted sites for sustainable development.

Automated summary

The experiment analyzed the impact of different doses of fly ash in soil on the growth performance, phenolics, flavonoids, and elemental uptake of Calendula officinalis. The results showed that low ratios of fly ash amendment to soil improved plant growth, while high fly ash doses tended to decrease growth parameters. A 40% concentration of fly ash did not contain toxic levels of elements and resulted in improved growth and yield. Additionally, increasing fly ash application up to 60% showed an increasing trend in phenolics and flavonoids in leaves.