Ionomics Analysis Reveals the Key Nutrient Elements Influencing Cadmium Uptake and Translocation in Wheat (Triticum aestivum)

To explore the key nutrient elements influencing cadmium (Cd) uptake and translocation in wheat plants, a hydroponic experiment was conducted to investigate the characteristics of the ionome (including Cd, Fe, Mn, Cu, Zn, P, S, K, Ca and Mg) in seedlings of ten wheat cultivars under different concentrations of Cd stress treatments. The relationships of ionomic variations with Cd uptake and translocation were also analyzed. The results reveal that, in comparison to the control group (no Cd stress), a 9-day exposure to 5 μmol·L^-1 Cd (low-concentration Cd stress) did not significantly impact the root and shoot growth of wheat seedlings. In contrast, 20 μmol·L^-1 Cd (high-concentration Cd stress) treatment for the same duration of exposure resulted in substantial inhibition of plant growth. Notably, considerable variability in Cd uptake and translocation was observed across the studied cultivars. Under low Cd stress, the differences in Cd uptake and the translocation factor among the ten wheat cultivars were 1.58 and 1.95 fold, respectively. These differences were further expanded to 2.15 and 2.44 fold, respectively, under high Cd stress. Compared with low Cd stress, high Cd stress altered one or more nutrient concentrations in the roots and shoots of some wheat cultivars. Moreover, the correlations of Cd uptake and translocation with the concentration of nutrient elements in wheat seedlings showed discrepancies between the low and high Cd treatments, indicating that Cd stress disrupts the ion network within wheat plants. Correlation and redundancy analyses reveal that under low Cd stress, Zn, P, and Mg are likely to be the critical nutrients influencing Cd uptake and translocation. Under high Cd stress, in addition to Zn, P, and Mg, elements such as S, Mn, Fe, and K also significantly contributed to wheat Cd uptake and translocation. These findings suggest that the types of key nutrients influencing Cd uptake and translocation in wheat are related to the degree of wheat Cd stress. Wheat seedlings adapt to Cd stress by physiologically and biochemically adjusting their internal element contents in response to the level of Cd exposure.