Effect of Pb Stress on Ionome Variations and Biomass in Rhus chinensis Mill

Abstract

This study examined changes in the ionome of Rhus chinensis in response to Pb stress so as to understand Pb phytotoxicity-related processes and provide theoretical support for improving the efficiency of this plant in remediating heavy metal-polluted soils. Rhus chinensis seedlings were cultured in pots with soil. The concentrations of 12 elements in the roots, stems, and leaves of the seedlings under treatments of 0, 500, and 1000 mg·kg−1 Pb(NO3)2 were determined. Principal component analysis (PCA), correlation analysis, and partial least squares path modeling (PLS-PM) were used to analyze the contributions of the affected elements in the ionomes of different organs of the seedlings under Pb stress. PCA showed that 74% of the total ionome variation was caused by the difference in organ types. N, Mg, K, Cu, Ca, and Zn were the important elements contributing to the variation of the ionome. Pb disturbed the ionome of different organs at varying levels, and the order of the interference levels between the organs was: stem > root > leaf. Correlation analysis showed that biomass had a significant positive correlation with N and K and a significant negative correlation with Pb, Mn, and the C:N ratio. Stem biomass had a significant positive correlation with Ca, Cu, and the N:P ratio. Root biomass had a significant negative correlation with the C:P ratio. PLS-PM analysis indicated that Pb stress had a major, direct, and inhibitory effect on biomass. The variation of ionomic profiles caused by Pb stress was mainly caused by the difference in organ types; the variation of the ionomic profiles of each organ was mainly caused by Pb stress. The elements that caused the variation of ionomic profiles varied with organ types, and the plant biomass was directly affected by a strong Pb poisoning effect and indirectly affected by a weak ionomic profile variation effect.