Intercropping with Solanum nigrum and Solanum photeinocarpum from Two Ecoclimatic Regions Promotes Growth and Reduces Cadmium Uptake of Eggplant Seedlings

Soil contamination by heavy metals is a serious environmental problem worldwide, and reduction of heavy metal accumulation in vegetables grown on contaminated land is a matter of urgency. A pot experiment was conducted to study the effects of intercropping with the Cd hyperaccumulators Solanum nigrum and Solanum photeinocarpum from two ecoclimatic regions, Ya'an and Chengdu, Sichuan Province, China, on the growth and cadmium (Cd) uptake of eggplant (Solanum melongena L.). The biomass, photosynthetic pigment contents, and activities of antioxidant enzymes of eggplant were enhanced by intercropping. The biomass of eggplant was the highest after intercropping with S. photeinocarpum from Ya'an, but did not differ significantly from that after intercropping with S. nigrum from Chengdu. The shoot Cd content of eggplant was significantly reduced by intercropping with the hyperaccumulators, which ranked as follows: S. nigrum from Chengdu > S. nigrum from Ya'an > S. photeinocarpum from Chengdu > S. photeinocarpum from Ya'an, with the decreases being 19.60%, 14.36%, 9.66%, and 6.42%, respectively, as compared with the control. The lowest shoot Cd content and translocation factor of eggplant were attained after intercropping with S. nigrum from Chengdu. Therefore, it was feasible to intercrop eggplant with S. nigrum and S. photeinocarpum on Cd-contaminated soil.