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Abstract:

Sunflowers are considered as hyper-accumulators of heavy metals and can be used in the phytoremediation of heavy metal contaminated soils. Wastewater is a valuable irrigation source in peri-urban and urban areas. However, it is contaminated with numerous heavy metals, which can be accumulated and translocated to different plant parts. Unfortunately, limited studies have assessed the accumulation and translocation of heavy metals in ornamental sunflower species. Therefore, the current study was conducted to infer the effects of different water sources (normal and wastewater) and water availability regimes (60% and 35% wetted soil) on the growth and heavy metal (zinc, manganese and chromium) accumulation in two sunflower species (cultivated and ornamental). The cultivated (Helianthus annuus L.) and ornamental (Helianthus giganteus L.) sunflower species were grown in pots and irrigated with normal and wastewater. Furthermore, the pots were maintained at two different water availability regimes (i.e., 60% and 35% wetted soil). Different growth traits such as root, shoot and total biomass, and achene weight were recorded. Furthermore, accumulation of zinc (Zn), manganese (Mn) and chromium (Cr) was noted in the roots, shoots and achenes of both species. Residual concentration of these metals in the soil was also assessed after the harvest of plants. Nonetheless, bioaccumulation and translocation factors of all metals were computed. The species, water sources and water availability regimes significantly differed for growth traits, heavy metals’ accumulation and bioaccumulation and translocation factors. Higher concentration of heavy metals in different plant parts were noted with normal water indicating that the metals were transported from soil rather than wastewater. Nonetheless, ornamental sunflower exhibited significant potential for the phytoremediation of Mn and Cr; thus, it should be explored further with in-depth studies.