蛇纹岩形成的土壤和在锌冶炼厂附近的土壤里,含有过量的重金属,如镉、铜、锌或镍(高岸等,1973;本间和白田,1977)等。在这种土壤里,桑树生长发育不良,经常发生象缺绿病和根叶畸形的显著病症(饭冡,1973;Shiba,1973)。另外,Bazzaz 等(1974a,b)报道了低浓度的镉、镍和铅能降低向日葵和玉米叶子的光合强度。为了弄清过量 Serpentine-forming soils and soils near zinc smelters contain excessive levels of heavy metals such as cadmium, copper, zinc or nickel (Takanai et al., 1973; Ben and Baita, 1977). In this soil, mulberry trees grow poorly and often develop significant symptoms like green-leaved and leaf-root deformities (Ito, 1973; Shiba, 1973). In addition, Bazzaz et al. (1974a, b) reported that low concentrations of cadmium, nickel and lead reduce the photosynthetic intensity of sunflower and maize leaves. To find out the excess