In order to study the difference of cadmium (Cd) accumulation in three species of Solanum, the Cd accumulation characteristics of Solanum nigrum L., Solanum alatum Moench and Solanum nigrum L. var. humile (Bernh.) C. Y. Wu et S. C. Huang were studied by pot experiment under the condition of Cd concentration of 10 mg/L. The results showed that the biomass of all parts of S. nigrum was significantly higher than that of other Solanum species, while the rank order of the Cd content of the Solanum species was as follows: S. nigrum var. humile > S. alatum > S. nigrum. The amount of Cd extracted by the Solanum species observed significant difference, and the amount of Cd extracted by the stems, leaves and shoots of S. alatum was significantly higher than other Solanum species, indicating that S. alatum had the best repair effect on Cd-contaminated soil.

In order to study the effect of mutual intercropping tomato on soil enzyme activity and available selenium content in selenium-containing soil, cherry tomatoes of red, yellow and purple varieties were selected for pairwise and three intercrops in this experiment respectively. The results showed that the activities of sucrase, phosphatase and urease in soil were increased after the three kinds of tomato were intercropped with each other, and the highest soil enzyme activity was found when red and purple tomatoes were mixed. Soil pH reached the maximum when three tomatoes were mixed. The content of available selenium in soil after intercropping tomato was higher than monoculture, and the content of available selenium was the highest when red and yellow tomatoes were mixed. Therefore, intercropping could improve the soil microecological environment, increase soil enzyme activity and increase available selenium content in tomato rhizosphere soil.

To determine if the uniconazole concentration(s) whether could enhance the cadmium (Cd) tolerance of Cyphomandra betacea seedlings, the effects of spray treatments with various uniconazole concentrations (0, 5, 10, 20, and 50 mg/L) on the physiological characteristics and Cd accumulation of C. betacea seedlings were studied in a hydroponic experiment. The results indicated that uniconazole significantly decreased the Cd content of C. betacea seedling stems, leaves, and shoots, but significantly increased the biomass of all analyzed seedling parts. Additionally, the leaf chlorophyll a, chlorophyll b, and carotenoid contents as well as the net photosynthetic rate, transpiration rate, stomatal conductance, and CO 2 concentration of intercellular were higher for the uniconazole-treated C. betacea seedlings than for the control seedlings. The optimal uniconazole concentration significantly promoted the superoxide dismutase, peroxidase, and catalase activities and the soluble protein content of C. betacea leaves. Moreover, uniconazole decreased the soluble sugar content of the C. betacea roots and stems, but had the opposite effect on the soluble sugar content of the leaves and shoots. The 20 mg/L uniconazole treatment resulted in the highest C. betacea seedling biomass and the lowest Cd content, indicating this concentration may be useful for improving C. betacea seedling growth in Cd-contaminated soils.

Diethyl aminoethyl hexanoate (DA-6) can lessen the effects of cadmium (Cd) toxicity on some plants. A pot experiment was conducted to examine the impact of different DA-6 concentrations (0, 10, 20, 30, and 40 mg/L) on growth and Cd accumulation of tomato seedlings. A DA-6 concentration of 10 mg/L increased the biomass of roots, stems, leaves, and shoots, while the other concentrations either had no significant effects or inhibited the growth of tomato seedlings. Concentrations 10 and 20 mg/L of DA-6 increased the chlorophyll b and total chlorophyll contents, and the activities of superoxide dismutase and peroxidase. All the four tested concentrations of DA-6 reduced catalase activity and increased the soluble protein content. Importantly, all tested DA-6 concentrations decreased the Cd content of tomato seedling roots, and increased in the Cd contents of stems, leaves, and shoots. While 10 mg/L DA-6 did not significantly affect the translocation factor of tomato seedlings, the other tested DA-6 concentrations enhanced the translocation factor. Therefore, 10 mg/L DA-6 could significantly promote the growth of tomato, but all the tested concentrations of DA-6 could also promote the uptake of Cd in tomato shoots, which could impede the safe production of tomatoes in Cd-contaminated soils.

To improve the ability of Cyphomandra betacea to accumulate selenium (Se), the effects of uniconazole (S3307) at different concentrations on the growth and Se accumulation of C. betacea seedlings were studied in this experiment. S3307 at different concentrations increased the biomass of C. betacea seedlings, and 20 mg L À1 S3307 had the best effect. The application of S3307 also increased the net photosynthetic rate, stomatal conductance, intercellular CO 2 concentration, transpiration rate, photosynthetic pigment (chlorophyll a, chlorophyll b, total chlorophyll, and carotenoid) content, and antioxidant enzyme (superoxide dismutase, catalase, and peroxidase) activity of C. betacea seedlings. Application of S3307 increased the Se content in the different organs of C. betacea seedlings to some extent. Besides, the different S3307 concentrations demonstrated a polynomial regression relationship with the root and shoot biomass and the root and shoot Se content. Besides, Se content of the various organs significantly positive correlated with the different organs' biomass. These results indicate that S3307 promotes C. betacea seedling growth and improves Se accumulation ability, with 20 mg L À1 demonstrating the highest response.