Effect of Cadmium Stress on the Growth and Cadmium Absorption Rules of Different Tobacco Varieties

【Objective】The research was conducted to explore the response of different varieties of tobacco to cadmium (Cd) stress, deeply understand the toxic effect of cadmium on tobacco, and provide a theoretical basis for the prevention and control of tobacco Cd pollution.【Method】With ten tobacco varieties as test materials, the agricultural properties, physiological and biochemical indexes and cadmium content under different concentrations of exogenous cadmium were analyzed by pot method.【Result】Cadmium stress promoted the growth of some tobacco varieties under low concentration and inhibited their growth under high concentration, while it showed inhibition effect on the rest of varieties. Among the tested varieties, Zhongyan 100 and Yuyan 10 were sensitive to cadmium stress, and the biomass reduction rates of Zhongyan 100 under high and low cadmium stress were 29.98% and 29.94%, and those of Yuyan 10 were 22.16% and 28.39%, respectively. With the increase of cadmium concentrations, the chlorophyll content, Pn, Gs and Tr of tobacco leaves showed a decreasing trend; while SOD activity, POD activity, MDA content and free proline content in tobacco leaves showed an increasing trend. Cadmium contents in all organs of tobacco increased with the increase of cadmium concentration, and the rule showed as: leaf > stem > root. In the whole growth period, cadmium content showed a trend of increasing first and then decreasing, and the highest value was obtained in the prosperous stage. The cadmium contents in leaves of Zhongyan 100, Yuyan 10 and Yuyan 13 were significantly higher than those of other varieties. The cadmium content in leaves of Yuyan 10 was highest (60.27 mg/kg) at a cadmium concentration of 3 mg/kg, while cadmium contents of Yunyan 87 and K326 were 38.88 mg/kg and 39.23 mg/kg, relatively low. At a cadmium concentration of 10 mg/kg, the cadmium contents in leaves of Zhongyan 100 and Yuyan 13 were 109.3 mg/kg and 101.3 mg/kg, relatively high. The cadmium content in leaves of Yunyan 105 was significantly lower (62.75 mg/kg) than that of other varieties. The enrichment capacity of tobacco showed a trend of increasing first and then decreasing after the growth period, and the enrichment coefficient reached the maximum value generally in the prosperous stage. The enrichment coefficient of Yuyan 10 was highest (18.6) at the cadmium concentration of 3 mg/kg, while the enrichment coefficients of Yunyan 87 and K326 were lower with values of 12.00 and 12.11; At the cadmium concentration of 10 mg/kg, the enrichment coefficient of Zhongyan 100 was highest with a value of 9.89, and enrichment coefficient of Yunyan 105 was lowest with a value of 6.13. The enrichment coefficient of Zhongyan 100 was 1.61 times that of Yunyan 105.【Conclusion】The varieties Zhongyan 100, Yuyan 10 and Yuyan 13 are sensitive to cadmium, while the varieties Yunyan 8, Yunyan 105 and K326 are resistant to cadmium.