Increased antioxidative enzyme activity mediates the phytoaccumulation potential of Pb in four agroforestry tree species: a case study under municipal and industrial wastewater irrigation

Abstract

Wastewater used as irrigation water is causing heavy metal accumulation in the agro-ecosystems. A greenhouse study was conducted to compare the phytoaccumulation ability of four agroforestry tree species under different wastewater treatments. Three-month-old potted seedlings of <i>Morus alba</i>, <i>Acacia nilotica</i>, <i>Acacia ampliceps</i>, and <i>Azadirachta indica</i> were irrigation with tap water (C), municipal wastewater (MWW), and industrial wastewater (IWW). Results showed that MWW had a positive and IWW had a negative impact on biomass production in all the species. <i>Acacia ampliceps</i> showed the highest increment (65%) and showed the lowest decrease (5%) in total biomass under both MWW and IWW treatment. Pb concentration was also found highest in the leaves, stem and roots of <i>Azadirachta indica</i> (108.5, 46.2, 180.5 mg kg^-1, respectively) under IWW. Production of H₂O₂ was highest in IWW treatment with almost 148% increase observed in <i>Azadirachta indica</i>. Similarly, the production of antioxidative enzymes (Superoxide dismutase, Catalase and Peroxidase) was also highest in <i>Azadirachta indica</i> under IWW. Therefore, results suggest that along with high increment in total biomass, both <i>Acacia ampliceps</i> and <i>Azadirachta indica</i> showed high Pb concentration and an effective antioxidative defense mechanism and thus, can be used for planting in soils irrigated with MWW and IWW.