Effects of Humic Acid and Edta on Phytoremediation, Growth and Antioxidant Activity in Rapeseed (Brassica Napus L.) Grown Under Heavy Metal Stress

Abstract

Rapeseed has been cultivated to produce non-edible and edible oil for thousands of years. It is known as the second-largest oilseed plant in the world with 24.6 million tons of oil production in 2021. The interventions that can be carried out during the cultivation of a plant with such a high production value are quite significant. Growth, enzymatic activities, and phytoremediation of rapeseed grown under heavy metal stress supported by humic acid (HA) and ethylenediaminetetraacetic acid (EDTA) applications were investigated for the first time in this study. Three doses of EDTA (EDTA1:5 mmol/kg, EDTA2:10 mmol/kg, EDTA3:15 mmol/kg) and three doses of HA (HA1:500 mg/kg, HA2:1000 mg/kg, HA3:2000 mg/kg) were applied in heavy metal treated pots. According to experiment results, HA1 and HA2 applications increased plant dry and fresh weights, root dry and fresh weights. However, EDTA applications caused a decrease in shoot length, a number of leaves, shoot fresh and dry weights, root fresh and dry weights. Bioconcentration factor (BCF) values for Zn, Cr and Cd we found higher than in both shoots and roots of rapeseed. For all levels of EDTA, the values of BCF (shoot) and BCF (root), transfer factor (TF) and translocation factor (TLF) increased compared to HA applications. On the other hand, in comparison to heavy metal polluted soils alone (PS), all levels of HA resulted in significantly reduced APX and CAT enzyme activity, and hydrogen peroxide (H2O2) and malondialdehyde (MDA) contents. We concluded that humic substances exert a significant influence on plant growth and reduce heavy metal toxicity in polluted soils. At the same time, HA could be more effective than EDTA in terms of phytoremediation of Cr. HA can increase phytoremediation in polluted soils as it improves plant growth and oxidative stress due to its organic nature. The results provide remarkable information for rapeseed cultivation in polluted regions.