Cosmos sulphureus Cav. is more tolerant to lead than copper and chromium in hydroponics system

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ORIGINAL PAPER

Cosmos sulphureus Cav. is more tolerant to lead than copper and chromium in hydroponics system N. Aftab1 · K. Saleem1 · A. H. A. Khan1 · T. A. Butt2   · C. R. Mirza2 · J. Hussain3 · G. Farooq4 · A. Tahir5 · S. Yousaf1 · M. I. Zafar1 · I. Nawaz5 · M. Iqbal1  Received: 6 May 2020 / Revised: 3 September 2020 / Accepted: 6 October 2020 © Islamic Azad University (IAU) 2020

Abstract  Heavy metals are environmental contaminants that have gained much attention globally. Plant growth and development are greatly affected by toxic heavy metals like lead, copper, and chromium. Cosmos sulphureus Cav. an ornamental plant was grown in hydroponics system against these metals. Plants were exposed to 2, 4, and 8 mg ­L−1 lead; 5, 10, and 15 mg ­L−1 copper, and 2.5, 5, and 10 mg ­L−1 chromium for 3 weeks using control as reference. Lead stress slightly affected the growth of C. sulphureus, however, had extreme signs of phytotoxicity due to copper and chromium. At 8 mg L ­ −1 lead, reductions by 21, 25, 45, and 38% in fresh and dry weight, shoot, and root length were observed, respectively, as compared to control while reductions due to copper/chromium (15/10 mg L ­ −1 in hydroponics) were 79/77, 90/73, 56/60, and 87/90%, respectively. Lead accumulated mostly in roots of C. sulphureus and was observed to be 1000 mg kg−1 at 8 mg L ­ −1. While copper −1 −1 and chromium were also accumulated mainly in roots and were 3 mg kg and 900 mg kg , respectively, at 10 mg L ­ −1 in external solution. C. sulphureus without lead-induced phytotoxic effects as well as higher accumulation in roots, strongly advocates this plant as a potential candidate of lead-hyperaccumulator; however, further investigations at the physiological and molecular level are needed to explore the mechanisms for lead homeostasis in roots. Graphic abstract

Editorial responsibility: Senthil Kumar Ponnusamy. Naveed Aftab, Kanza Saleem contributed equally. Electronic supplementary material  The online version of this article (https​://doi.org/10.1007/s1376​2-020-02981​-w) contains supplementary material, which is available to authorized users. Extended author information available on the last page of the article

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International Journal of Environmental Science and Technology

Keywords  Accumulation · Heavy metal · Ornamental plants · Phytoremediation · Phytostabilization

Introduction The term heavy metal implies to metals and metalloids that have a density of more than 5 g cm−3 (Nie et al. 2016). Usually, they are a poorly defined group of inorganic chemicals and most of them are commonly found at contaminated sites. Heavy metals have the potential to cause harm because of their persistivity and ability to accumulate within plant’s body (Nie et al. 2016). Heavy metals usually stay in the upper layer of soil because of the ability of large organic horizons to bind these molecules (Ashraf et al. 2019), as a result, they are easily taken up by plants and thus the adsorption process of essential nutrients ­(Cu2+, ­Fe2+, ­Mn2+ and ­Zn2+) is