Effects of intercropping with Youngia erythrocarpa, Conyza canadens and Mazus japonicus on physiological and biochemical characteristics of Galinsoga parviflora under cadmium stress

A pot experiment was conducted to study the effects of intercropping with Youngia erythrocarpa, Conyza canadens and Mazus japonicus on physiological and biochemical characteristics of hyperaccumulator Galinsoga parviflora under cadmium (Cd) stress. The results showed that intercropping with Y. erythrocarpa (GIY), C. canadens (GIC) and M. japonicus (GIM) all increased the superoxide dismutase (SOD), peroxidase (POD), peroxidase (CAT) activity and the soluble protein content of G. parviflora compared with monoculture (MG), the photosynthetic pigment (chlorophyll a, chlorophyll b, total chlorophyll, carotenoid) content and chlorophyll a/b of G. parviflora increased after intercropping, too. Among all treatments, GIC had the highest antioxidant enzyme activity, soluble protein content and photosynthetic pigment content. As for photosynthetic characteristics, GIC had the highest net photosynthetic rate (Pn), followed by GIY, GIM and MG. Compared with MG, the stomatal conductance (Gs) and transpiration rate (Tr) of GIC and GIM all increased significantly while that of GIC had no significant change, moreover, GIC had significantly lower CO2 concentration of intercellular (Ci) than other treatments, there was no significant difference in value of pressure deficit leaf (Vpdl) among all treatments. Therefore, under Cd stress, intercropping with C. canadens can improve the antioxidant enzyme activity and photosynthetic capacity of G. parviflora to the greatest extent, which was conducive to its remediation of Cd contaminated soil.