Activation and tolerance of Siegesbeckia Orientalis L. rhizosphere to Cd stress

Jianyu Xie; Xiaoxun Xu; Shirong Zhang; Zhanbiao Yang; Guiyin Wang; Ting Li; Yulin Pu; Wei Zhou; Changlian Xu; Guochun Lv; Zhang Cheng; Junren Xian; Zhien Pu

doi:10.3389/fpls.2023.1145012

Activation and tolerance of Siegesbeckia Orientalis L. rhizosphere to Cd stress

Front Plant Sci. 2023 Mar 24:14:1145012. doi: 10.3389/fpls.2023.1145012. eCollection 2023.

Authors

Jianyu Xie¹, Xiaoxun Xu^{1

2}, Shirong Zhang^{1

2}, Zhanbiao Yang^{1

2}, Guiyin Wang^{1

2}, Ting Li³, Yulin Pu³, Wei Zhou³, Changlian Xu¹, Guochun Lv¹, Zhang Cheng¹, Junren Xian¹, Zhien Pu⁴

Affiliations

¹ College of Environmental Sciences, Sichuan Agricultural University, Chengdu, China.
² Key Laboratory of Soil Environment Protection of Sichuan Province, Chengdu, China.
³ College of Resources, Sichuan Agricultural University, Chengdu, China.
⁴ College of Agronomy, Sichuan Agricultural University, Chengdu, China.

Abstract

This experiment investigated the changes of rhizosphere soil microenvironment for hyperaccumulation-soil system under Cd stress in order to reveal the mechanism of hyperaccumulation and tolerance. Thus, Cd fractions, chemical compositions, and biochemical characteristics in rhizosphere soil of Siegesbeckia orientalis L. under Cd stress conditions of 0, 5, 10, 25, 50, 100, and 150 mg kg-1 were investigated through a root bag experiment, respectively. As a result, Cd induced the acidification of S. orientalis rhizosphere soil, and promoted the accumulation of dissolved organic carbon (DOC) and readily oxidizable organic carbon (ROC), which increased by 28.39% and 6.98% at the maximum compared with control. The percentage of labile Cd (acid-soluble and reducible Cd) in soil solution increased significantly (P < 0.05) from 31.87% to 64.60% and from 26.00% to 34.49%, respectively. In addition, rhizosphere microenvironment can alleviate the inhibition of Cd on soil microorganisms and enzymes compare with bulk soils. Under medium and low concentrations of Cd, the rhizosphere soil microbial biomass carbon (MBC), basal respiration, ammonification and nitrification were significantly increased (P < 0.05), and the activities of key enzymes were not significantly inhibited. This suggests that pH reduction and organic carbon (DOC and ROC) accumulation increase the bioavailability of Cd and may have contributed to Cd accumulation in S. orientalis. Moreover, microorganisms and enzymes in rhizosphere soils can enhance S. orientalis tolerance to Cd, alleviating the nutrient imbalance and toxicity caused by Cd pollution. This study revealed the changes of physicochemical and biochemical properties of rhizosphere soil under Cd stress. Rhizosphere soil acidification and organic carbon accumulation are key factors promoting Cd activation, and microorganisms and enzymes are the responses of Cd tolerance.

Keywords: Cd; Siegesbeckia orientalis; bioavailability; hyperaccumulator; phytoremediation; rhizosphere.

Grants and funding

This work was supported by the Key Research and Development Projects of Sichuan Province, China (Grant No. 2021YFN0018); Project of Scientific and Technological Innovation Research and Development, Chengdu (Grant No. 2021-YF05-00959-SN).