Effects of Cadmium Stress on the Growth and Physiological Characteristics of Sweet Potato in the Whole Growth Period

Abstract

This study evaluated the responses of sweet potatoes to Cd stress through pot experiments, thus laying a theoretical foundation for their comprehensive utilization in Cd-polluted cultivated land. Four treatments were designed in the experiments, i.e., CK and three Cd stress treatments (T1, T2, and T3) with Cd concentrations of 3, 30, and 150 mg/kg, respectively. Through analyzing the individual plant growth, photosynthesis, antioxidant capacity, carbohydrate Cd accumulation distribution, and other indicators of sweet potato at different growth periods, the characteristics of sweet potato carbon metabolism in response to Cd stress during the whole growth period were explored. The results showed that T2 and T3 treatments inhibited the vine length, leaf area, stem diameter, and tuberous root growth of sweet potato, while T3 treatment significantly increased the number of sweet potato branches. Under Cd stress, the synthesis of chlorophyll in sweet potato was significantly inhibited, while the activity of the Rubisco enzyme was significantly reduced. As the Cd concentration increased, the function of PS II was also affected. The soluble sugar content showed no significant change in low Cd concentration treatments but decreased significantly under high Cd concentrations; the tuberous root starch content decreased significantly with the increase in Cd concentration. During the whole growth period, the activities of catalase (CAT), peroxidase (POD), and superoxide dismutase (SOD) increased significantly in T2 and T3 treatments, while the SOD activity in T1 treatment was significantly lower than that of CK. With the increase in Cd concentration, the Cd contents of various sweet potato organs exhibited increasing trends. The absorbing roots had the highest bioconcentration factor, the tuberous roots had a lower bioconcentration factor and Cd accumulation, and the transfer factor from stem to petiole was the highest. These results showed that sweet potatoes had a high Cd tolerance and a certain restoration potential for Cd-contaminated cultivated land.