Phytoremediation capacity of Tagetes patula L. under constant exposure to zinc, nickel and chromium in irrigation water

Abstract

The pot experiment was conducted to study the phytoremediation capacity and to evaluate the response of Tagetes patula L. under the conditions of constant input of high concentrations of Zn, Cr and Ni into the soil with irrigation water. Tagetes patula could thrive well at high levels of Zn (232–1356 mg/kg), Cr (241 ± 35.2 mg/kg) and Ni (118 ± 1.46 mg/kg) in the soil during 28 days, with Ni (19.9 ± 7.79 mg/kg dry weight), Zn (114–661 mg/kg dry weight) and Cr (77.1 ± 23.8 mg/kg dry weight) accumulated mainly in plant roots. By the end of the experiment, Cr content in the roots and shoots, as well as Ni in all parts of the contaminated Tagetes patula samples, was approximately 200 and 100 times, respectively, higher than in the control samples. The average values of bioconcentration factor (BCF) were < 1, with the maximum accumulation capacity observed for Zn (BCF ⁓ 0.65) and the minimum one for Cr (BCF ⁓ 0.06). High concentrations of Ni had a stimulating effect on chlorophyll synthesis in leaves and phenolic compounds in flowers of Tagetes patula. On the contrary, the decrease in chlorophyll and phenolic compounds in Tagetes patula leaves was a response to exposure to high Zn and Cr content. The antioxidant response of Tagetes patula, in particular the increased 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging capacity of leaves and tissue-specific responses in the 2,2’-Azino-di-(3-ethylbenzthiazoline sulfonic acid) (ABTS) assay at high Zn and Ni content in soil, may serve as a functional indicator of physiological involvement in remediation processes.