Cadmium (Cd) accumulation in Solanum nigrum L. is known to occur mainly in cell walls and vesicles. However, limited research has been conducted on the toxic effects of Cd specifically targeting mitochondria in S. nigrum leaves. This study aims to delineate the impact of Cd accumulation on mitochondrial structure and function in S. nigrum leaves, thereby providing a theoretical foundation for enhancing its application in phytoremediation of Cd-polluted soils. The results showed that the Cd content in mitochondria would gradually reach saturation with the increase of Cd treatment concentration. However, the accumulation of Cd led to osmotic pressure imbalance and morphological changes within mitochondria, which in turn caused a series of impairments in mitochondrial function. Cd severely damaged the energy metabolism function of mitochondria, especially under 200 mu M CdCl2 stress, the mitochondrial ATP content decreased by 90.65 % and the activity of H+-ATPase decreased by 80.65 %. Furthermore, reactive oxygen species (ROS) in mitochondria accumulated mainly in the form of H2O2. Compared with the non-Cd control group, the H2O2 content in the Cd-treated groups (50, 100, and 200 mu M CdCl2) increased by 61.62 %, 186.69 %, and 405.81 %, respectively. The inhibition of cellular respiration by Cd and the sharp increase in ROS exacerbated the oxidative damage in mitochondria. Interestingly, the activities of mitochondrial peroxidase (POD) and dehydroascorbate reductase (DHAR) exhibit remarkable tolerance under Cd stress. Based on these results, we believe that Cd can cause dysfunction and oxidative damage to the mitochondria of S. nigrum leaves.

Soil cadmium (Cd) pollution is a serious ecological problem worldwide. Understanding Cd-detoxification mechanisms in woody plants will help to evaluate their tolerance ability and phytoremediation potential to Cd-polluted soils. This study investigated the growth, physiochemistry, Cd distribution, and transcriptome sequencing of male and female poplars under three Cd levels (0, 50, and 100 mg & sdot;kg-1). The results showed that Cd stress significantly inhibited the growth of aboveground parts. Over 70 % of the Cd was distributed in the cell wall fraction of roots, stems, and leaves, with the majority accumulating in the roots. Poplars can conjugate Cd with phytochelatins to reduce Cd damage, which is more evident in males than females. The antioxidant defense system of females is more effective than that of males at reducing the damage from Cd. Females demonstrated a stronger Cd-regulation ability than males under the 100 mg & sdot;kg- 1 Cd treatment. Sex-specific responses to Cd were associated with differential gene expression. Under Cd stress, the genes related to oxidation-reduction processes, antioxidant enzyme activity and defense mechanisms, cell wall synthesis, and glutathione metabolism were mainly enriched and upregulated in females, whereas in males, genes related to photosynthesis and photosynthetic pigment biosynthesis were mainly enriched and downregulated, indicating greater damage to the photosynthetic system than in females. Our study provides novel insights into the mechanisms responding to Cd tolerance in poplars. Further studies should be carried out to assess the impact of soil Cd pollution on the wood quality of poplars.