In this study, the effects of ethylenediaminetetraacetic acid (EDTA) and humic acid (HA) chelate applied to soils contaminated with heavy metals on the development, antioxidant defence system, and phytoremediation of forage turnip (Brassica rapa L.) were investigated for the first. Three doses of EDTA (E 1 : 5 mmol/kg, E 2 : 10 mmol/kg, E 3 : 15 mmol/kg) and three doses of HA (HA 1 : 500 mg/kg, HA 2 : 1 000 mg/kg, HA 3 : 2 000 mg/kg) were applied to soils contaminated with heavy metals (Cd, Pb, Zn, and Cr) in the pot. According to experiment results, HA application as chelate to the polluted soil caused a significant increase in the growth of forage turnip. Phytoremediation values of the plant for Cd heavy metal were found to be BCF shoot , BCF root > 1, and translocation factor > 1. This result proved that forage turnip has Cd accumulating properties. Also, HA application caused a decrease in H 2 O 2 (46%) and malondialdehyde (6%) levels and antioxidative enzyme activity in polluted soil. It has been concluded that humic acid improves the oxidative stress conditions in the plant and is more effective in the development and growth of the plant than EDTA, so that it can be used effectively in phytoremediation studies.

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.

The aim of this study was to investigate the effects of humic acid (HA) applications on rapeseed (Brassica napus L.) growth, heavy metal uptake, bioconcentration factor (BCF), translocation factor (TF), tolerance index (TI), catalase (CAT), ascorbate peroxidase (APX) enzyme activities and hydrogen peroxide (H2O2) content in polluted soil with lead (Pb), chromium (Cr), cadmium (Cd), and zinc (Zn). Three doses of HA (Control, HA1:500 mg kg-1, HA2:1000 mg kg-1, HA3:2000 mg kg-1) were applied in pots. HA1, HA2, and HA3 applications increased plant growth parameters compared to polluted soil. Compared to the control, HA applications in polluted soil increased the Pb, Cr, Cd, and Zn concentrations in the plant. However, HA applications in polluted soil significantly decreased the heavy metal content in roots and shoots of the plant compared to polluted soil. BCF in both roots and shoots of the plants were greater than 1 for Pb, Cr, Cd, and Zn. However, specifically HA2 application decreased the shoot and root BCF values in polluted soil. TF was smaller than 1 in Pb, Cr, Cd, and Zn in polluted soil. On the other hand, HA applications for Cd increased TF values. Shoot TI decreased 17.37 %, and root TI decreased 9.09% in polluted soil. CAT and APX enzyme activities and H2O2 increased significantly in polluted soil. However, HA applications decreased CAT and APX enzyme activities and H2O2 content in rapeseed. It is concluded that HA application in Pb, Cr, Cd, and Zn polluted soil has a remedial effect on the development of rapeseed by reducing heavy metal content and oxidative stress.

Cadmium (Cd) and chromium (Cr) pollution severely limit the productivity of rapeseed (Brassica napus L.). A synergistic strategy combining biochar and arbuscular mycorrhizal fungi (AMF), applied with or without humic acid, was evaluated in greenhouse soil spiked with 50 mg kg⁻¹ Cd and Cr. AMF inoculation increased shoot dry weight by 36% and the Cd bioconcentration factor by 11% relative to polluted controls. Adding biochar or humic acid further elevated shoot- and root-BCF for Cd and Cr by 25–80% and raised the transfer factor above 1.2, indicating efficient root-to-shoot metal translocation. Total accumulation concentration doubled compared with AMF alone. The humic-acid + AMF treatment reduced malondialdehyde by 36% and moderated superoxide dismutase, catalase, and ascorbate peroxidase activities, evidencing lower oxidative stress. Overall, integrating AMF with biochar or humic acid enhanced biomass, mitigated oxidative damage, and strengthened phytoremediation capacity, offering a practical solution for Cd/Cr-contaminated, low-organic-matter soils.

This study aimed at investigating the effects of selenium (Se) against cadmium (Cd) toxicity on the plant growth, antioxidative enzyme activity, and Cd and Se content in lupine (Lupinus albus L.) plant and soil. The experiment was carried out under controlled conditions according to the factorial experiment design. Two doses of Cd (Cd1:25 mg kg-1and Cd2:50 mg kg-1) were applied in the soil. Three doses of Se (Se1:2,5 mg kg-1 Se2: 5 mg kg-1, and Se3:10 mg kg-1) were applied to the Cd-treated pots. Two-way analysis of variance was conducted to explore the interactions between Cd and Se doses. The results showed that Cd1 and Cd2 applications alone caused a decrease in plant growth as well as increased oxidative stress due to shoot and root Cd content in plants and soil. Se1 and Se2 applications to Cd-treated pots caused an increase in shoot and root length, fresh and dry shoot weights, fresh and dry root weights. However, Se3(10 mg kg-1) application decreased shoot and root length, fresh and dry shoot weights, fresh and dry root weights. More importantly, application of Se (2,5 mg Se kg-1 and 5 mg Se kg-1) is effective in improving the toxicity of cadmium increasing plant growth and diminishing shoot and root Cd, MDA content and DTPA-Cd content in lupine plant. We concluded that low and medium levels of Se alleviated the toxic effects of Cd in lupine. But high level of Se exerted negative influence on plant growth and oxidative stress under Cd toxicity. Moreover the effectiveness of selenium in reducing cadmium toxicity depends on the dose as well as the form of application.