12 / 2021-06-18 20:34:38

Effects of potentially toxic metals (PTMs) on physiological response, and PTMs subcellular distribution and chemical forms of Symphytum officinale L.

heavy metals; chemical forms; subcellular distribution

Effects of potentially toxic metals (PTMs) on physiological response, and PTMs subcellular distribution and chemical forms of Symphytum officinale L.

Xuejia Wang^1,a, Juan Du^1,a, Ronghua Li^a, Di Guo^a, Weidou, Guan^a, Yaqiong Xu^a, Jingwen Wang^a, Yichen Zhang^a, Zengqiang Zhang<sup>a,*

a</sup> College of Natural Resources and Environment, Northwest A&F University, Yangling, Shaanxi 712100, China

¹ Both authors contributed equally to this work.

^*Corresponding author:

Prof. Z. Q. Zhang,

College of Natural Resources and Environment,

Northwest A&F University, Yangling,

Shaanxi Province 712100, PR China

Tel./Fax: +86 13609254113; +86 02987080055.

E-mail address: zhangzq58@126.com (Z. Q. Zhang)

The accumulation, resistance and stress response associated with the toxic heavy metals (Cd, Pb, and Zn) of Symphytum officinale L. were investigated by hydroponic experiments. Symphytum officinale L. were cultivated in nutrient solution with the addition of Cd (10 mg• L^-1), Pb (15 mg• L^-1), and Zn (50 mg• L^-1), respectively. The results showed that there was a decreasing trend of the chlorophyll content of plant leaves under the stress of toxic heavy metals (Cd, Pb, and Zn). The concentration of malondialdehyde (MDA) in the plant leaves contained PTMs were significantly higher than the control sample. The existence of potentially toxic metals (PTMs) also led to the increase of activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) in the Symphytum officinale L.. The results of PTMs subcellular distribution displayed that the PTMs were primarily stored in the cell wall in the plant roots, while the PTMs were compartmentalized into the soluble fractions in the leaves. Additionally, Cd was mainly extracted in the forms of inorganic, water soluble organic acid, and undissolved phosphate. Pb primarily existed in inorganic form. The dominant forms of Zn were inorganic and undissolved phosphate. The resistance mechanism, and the subcellular distribution and chemical forms of PTMs indicated the accumulation of PTMs in Symphytum officinale L., which provided a theoretical basis for its application in contaminated soils.

Keywords: heavy metals; chemical forms; subcellular distribution