Screening of various Brassica species for phytoremediation of heavy metals-contaminated soil of Lakki Marwat, Pakistan

Natural resources, especially agrarian soils, have been much contaminated with various pollutants including heavy metals since industrial revolution, so it is pertinent to utilize green technology, the so-called phytoremediation technology for reclamation of heavy metal-contaminated soils. A pot experiment was conducted to screen four different species (Brassica juncea, Brassica napus, Brassica rapa, Brassica campestris) of Brassicaceae family for the remediation of HMs contaminated soil of Lakki Marwat city, Pakistan, irrigated with municipal wastewater. Plants were analyzed for various morpho-physiological, biochemical, and phytoextraction factors like bioaccumulation (BAF) and translocation factor (TF). Results showed maximum morpho-physiological responses including seed germination, chlorophyll content, root fresh and dry weights, and shoot fresh and dry weights in B. juncea followed by B. napus, B. campestris, and B. rapa. Plant biochemical analyses of antioxidant enzymes including superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) also exhibited maximum activity in B. juncea followed by B. napus, B. campestris, and B. rapa, respectively, in both control and contaminated soils. Conversely, plant oxidative stress markers including malondialdehyde (MDA) and hydrogen peroxide (H₂O₂) showed maximum contents in B. rapa followed by B. campestris, B. napus, and B. juncea in both soils. Plant bioconcentration factors i.e. BAF and TF measured for all species in both soils confirmed that B. juncea accumulated maximum heavy metals. Similarly, enhanced phytoextraction capacity was noticed for all Brassica species in decreasing order i.e. B. napus > B. campestris > B. rapa. Hence, all the results confirmed that B. juncea excelled and can be recommended for phytoremediation purpose in soils of study area.