Effect of cadmium stress on the absorption and transportation of metal micronutrient elements in Hybrid Pennisetum

To explore the response mechanism of Pennisetum americanum × P. purpureum to cadmium (Cd) stress, pot experiments were conducted to study the effects of different concentrations of Cd on the accumulation of micronutrient elements including iron (Fe), zinc (Zn), manganese (Mn), and copper (Cu). The results showed that 1) Cd significantly inhibited the growth of P. americanum × P. purpureum and decreased the plant height, tiller number, and dry matter yield (P < 0.05); 2) compared to the control, 26 mg·kg⁻¹ Cd had no significant effect on the content of Fe, Zn, Mn, and Cu in the roots, whereas 70 mg·kg⁻¹ Cd significantly increased the content of Fe, Zn, and Mn in the roots by 97.69%, 45.14%, and 13.00% respectively; 3) Cd stress significantly reduced the content of Mn by 29.30%～32.23% but had no significant effect on the content of Fe, Zn, and Cu in aerial parts; 4) Cd stress increased the bioconcentration factor (BCF) value of Fe and Zn in the root, decreased the BCF value of Zn and Mn in the aerial part, and inhibited the transport of Fe, Zn, and Mn from the roots to aerial parts; 60～70 mg·kg⁻¹ Cd significantly inhibited the upward transport of Cu in P. americanum × P. purpureum; and 5) the activity of nitrate reductase decreased, however, the activity of glutathione peroxidase increased significantly. The results showed that P. americanum × P. purpureum had good tolerance for Cd stress and did not significantly change the levels of Fe, Zn, and Cu; inhibited the levels of Mn, and changed the activities of Mn-related enzymes greatly. These results provide a scientific basis for developing physiological control materials with the function of alleviating Cd toxicity.