The positive effects of humic acid (HA) in alleviating the toxicity of cadmium (Cd) were demonstrated in pot grown Hybrid Pennisetum. Twelve treatments consisting of six concentrations of Cd (0, 10, 20, 50, 70 and 100 mg kg⁻¹) combined with two levels of HA (0 and 1.0 g L⁻¹) were applied. Our results showed that although Cd toxicity significantly inhibited plant growth, decreased the dry weights of leaves, stems and roots and substantially increased the leaf malondialdehyde (MDA) and Cd concentrations in different plant tissues, Hybrid Pennisetum had a strong ability in the uptake and transfer of Cd and could be used for phytoremediation in Cd-contaminated soils. The chlorophyll content and photosynthetic capacity of the leaves also decreased under Cd stress. The foliar application of HA alleviated the symptoms of Cd toxicity by increasing the net photosynthetic rate (P_n) and the content of photosynthetic pigments, although HA did not significantly decrease the concentration of Cd in the leaf, stem and root tissues. Compared with the zero-HA treatment, 1.0 g L⁻¹ HA increased the root, stem and leaf biomasses by approximately 2.7–99.4%, 3.9–11.2% and 18.2–87.1%, respectively. MDA had a significant negative relationship with P_n. The MDA content of the HA-treated Hybrid Pennisetum plants decreased by approximately 4.4–12.2% compared with that of the Cd-only plants, indicating the high Cd tolerance of Hybrid Pennisetum. It is concluded that foliar application of HA (1.0 g L⁻¹) can alleviate Cd toxicity and increase Cd stress tolerance in Hybrid Pennisetum, thereby lowering the potential risk of soil Cd contamination.

在盆栽杂交狼尾草中证明了腐殖酸（HA）减轻镉（Cd）毒性的积极作用。进行了十二种处理，包括六种浓度的Cd（0、10、20、50、70和100 mg kg ^-1）和两种水平的HA（0和1.0 g L ^-1）。我们的结果表明，尽管Cd毒性显着抑制了植物的生长，但降低了叶片，茎和根的干重，并显着增加了不同植物组织中叶片的丙二醛（MDA）和Cd的浓度，杂交狼尾草具有很强的Cd吸收和转移能力，可用于Cd污染土壤的植物修复。在镉胁迫下，叶片的叶绿素含量和光合能力也降低。叶面喷施HA可以通过增加净光合速率（P _n）和光合色素含量来减轻Cd毒性症状，尽管HA并不能显着降低叶片，茎和根组织中Cd的浓度。与零HA处理相比，1.0 g L ^-1 HA分别使根，茎和叶的生物量分别增加了约2.7–99.4％，3.9–11.2％和18.2–87.1％。MDA与P _n呈显着负相关。经HA处理的杂种的MDA含量与仅含镉的植物相比，狼尾草植物减少了约4.4-12.2％，这表明杂交狼尾草对镉的耐受性很高。结论是，叶面施用HA（1.0 g L ^-1）可以减轻杂交狼尾草的Cd毒性并提高Cd胁迫耐受性，从而降低土壤Cd污染的潜在风险。