Responses and tolerance mechanisms of K. paniculate seedlings under lead stress: physiological indicators, morphological distribution, enrichment effects and microstructure

Abstract

Phytoremediation could be an alternative strategy for lead (Pb) contamination, The physiological mechanisms of plant resistance to Pd contamination are of less concern. In this study, Different concentrations of Pb solutions were added to explore the growth of Koelreuteria paniculate (Sapindaceae). physiology and microstructure of K. paniculate were determined. The results showed that plant growth increased up to 123.8% and 112.7% relative to the control group when the lead concentration was 200 and 400 mg/L. In all treatments, most of the Pb accumulation reached 81.31%-86.69% in the roots and slightly lower concentrations in the above-ground leaves than in the stems. Transmission electron microscopy (TEM) showed that Pb accumulates in the inactive metabolic parts (cell walls and vesicles) in roots and stems, which may be the main mechanism for plants to reduce Pb biotoxicity. In addition, by Fourier transform infrared spectroscopy (FTIR), Pb stress increased the content of intracellular -OH and -COOH functional groups, including compounds such as organic acids, polysaccharides and proteins that bind to Pb, attenuating the toxicity to plants and enhancing their adaptation and tolerance to heavy metals.

Insights into the Mechanisms Involved in Lead (Pb) Tolerance in Invasive Plants—The Current Status of Understanding

“…However, there have been reports of decreased biomass allocation, which can be attributed to heavy metal concentrations in the soil and the growth strategies adopted by different plant species. This can lead to lower absorption or avoidance of pollutant uptake by roots [60][61][62]. In fact, Yang, et al [63] found that invasive species, such as Biden frondosa, Erigeron Canadensis, Alternanthera philoxeroides and Cynodon dactylon, accumulated significantly lower levels of Pb in both roots and shoots compared to native species.…”