Physiological responses of certain ornamental plants to sludge and artificial topsoils derived from flyash, sludge, and rengam series subsoil

Abstract

In this study, four artificial topsoil mixtures were produced by mixing incinerator flyash, sewage sludge, and subsoil (from granite origin) in various proportions. Each mixture had a different heavy metal content. Both sludge and the artificial topsoils were used to grow certain ornamental plants, namely, Bougainvillea spectabilis, Ixora coccinea, and three Heliconia taxa; H. psithacorum x H. spathocircinata cv. “Golden Torch”;, H. rostrata and H. psithacorum cv. “Tay”;. Their physiological responses were monitored using chlorophyll fluorescence Fv/Fm ratio and their general appearance was also recorded. All the five plants grown in sludge were observed to show no symptoms of heavy metal toxicity. However, it was found that I. coccinea and all three Heliconias were susceptible to heavy metal toxicity when grown in all the four mixtures of artificial topsoil. Bougainvillea spectabilis is capable of tolerating the heavy metal present in the artificial topsoil with the least amount of heavy metals but they showed different levels of toxicity symptoms when grown at the other three mixtures with higher heavy metal content. These findings indicate that B. spectabilis is the most tolerant plant to heavy metals among the tested plants grown in the different artificial topsoils.

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