CADMIUM AND LEAD ACCUMULATIONS BY TYPICAL CULTIVARS OF WATER SPINACH UNDER DIFFERENT SOIL CONDITIONS

The typical cultivars of water spinach (Ipomoea aquatica Forsk.) with different Cd-accumulating abilities (two Cd-PSCs, cv. Qiangkunliuyeqinggu (QLQ) and cv. Qiangkunliuyebaigu (QLB), and one non-Cd-PSC, cv. Taiwan 308 chunbailiuye (T308)) were used to investigate Cd and Pb accumulations under different soil conditions. Variations of biomasses (DW) of both shoots and roots from cultivars were significant (p < 0.001). Average Cd concentrations in shoots in both the first and second harvest were in the order of T308 > QLB > QLQ, while those in roots of cv. QLQ and cv. QLB were mostly high. The average shoot Cd concentrations in the Cd-PSCs were always lower than in the non-Cd-PSCs unrelated to soil conditions and harvest timings, indicating that the variation in Cd accumulation among cultivars is genotype-dependent and less affected by soil properties. The average values of Cd TRs and TFs were lower in the Cd-PSCs than in the non-Cd-PSC, suggesting that Cd accumulation in different cultivars is associated with the ability of Cd uptake from soil to plant as well as translocation from root to shoot. Variation of shoot Pb concentration in cultivars was not significant (p > 0.05) for both the first and second harvests, indicating that the variations in Pb accumulation among the tested cultivars are much smaller than those in Cd accumulation. It was found that among the detected soil variables, soil pH, soil CEC and total and available P could be raised as the crucial factors affecting Pb accumulation in shoots of water spinach.