Abstract:

Objective: This study aims to investigate the ionomic responses in four cultivars of Salix integra under cadmium (Cd) stress, so as to provide a theoretical basis for selecting high Cd-enriched S. integra, and improving the remediation efficiency for heavy metal contaminated soil. Method: A hydroponic experiment was conducted to analyze the variation of Cd, macro elements (N, P, K, Ca, Mg), and trace elements (Fe, Zn, Cu, Mn, Mo, Se) contents in roots, cuttings, new branches and leaves of four cultivars of S. integra under 0, 10, and 50 μmol·L^?1 of Cd(NO₃)₂ treatments. Combined with principal component analysis, correlation analysis and partial least squares regression analysis were performed to identify the elemental contribution of ionomic variation in different tissues under Cd stress and influence on accumulation of Cd and translocation of the major elements in S. integra. Result: 1) The coefficient of variation (CV) of macro elements, especially N, was significantly smaller than that of the other elements, and the CV of Cd in leaf tissue was significantly higher than that in the other tissues. The CVs of divalent cations such as Mn, Zn and Fe under Cd stress were all greater. 2) PCA analysis revealed that 78.3% of the total variation in the ionome of S. integra was caused by the tissue types, among which Zn, Fe, Cu, Mn and Mo were important components of the variation in the ionome of S. integra. 3) The degree of interference of Cd treatments on different tissue ionome was: root > leaf > new branch > cutting. Results also showed that Cd content in the leaves was significantly and positively correlated with Fe and Mg; Cd content in the new branches and cuttings was significantly and positively correlated with N and Se; Cd content in the roots was significantly and positively correlated with Ca, Cu and Se. Cluster analysis and partial least squares regression confirmed that N, P, Ca, K, Mn, Fe, Mg and Mo played an important role in Cd translocation in S. integra. Conclusion: The ionomic variation in S. integra caused by Cd stress mainly originates from the differences among tissue types. In the same tissue, the ionomic variation mainly originates from Cd stress. Moreover, the main elements that cause ionomic variation vary in different tissues. The transport of Cd in S. integra is affected by ionomic variation, among which the macro elements of N, P, K, Ca, Mg, and the trace elements of Mn, Fe and Mo play an important role in the transport of Cd in S. integra.

Key words: cadmium stress, Salix integra, ionome, mineral elements, cadmium transport