The Effect of Cadmium Toxicity on the Development of Lettuce Plants on Contaminated Sod-Podzolic Soil

The influence of cadmium on the morphometric and biochemical indicators of the development of lettuce of the Moscow greenhouse variety, on productivity and also on metal accumulation in plant biomass during cultivation on sod-podzolic soil polluted with this toxicant in the doses range from 2 to 100 mg/kg was studied. It was shown that cadmium has a toxic effect on the development of lettuce: the plant height was reduced by 29.7–77.5%, the number of leaves was reduced by 16.4–61.3%, and the leaf surface area decreased by 34.5–99% depending on the level of contamination. The presence of metal in the soil in concentrations 5–100 mg/kg caused a decrease of the content of chlorophyll a by 15.6–38.1% in plants; chlorophyll b content decreased by 18–20% at cadmium concentration 10–100 mg/kg; carotenoids decreased by 40% at concentrations 20–50 mg/kg. Cadmium contributed to a decrease in free proline content by 20–26% with Cd concentrations at 5–100 mg/kg of soil; at a concentration of 2 mg/kg, on the contrary, Cd caused an increase of proline content of 66.2% and malondialdehyde content of 59.9% in comparison with the control. Productivity of plants decreased by 49.6–99.6% at all studied concentrations, and the level of metal accumulation in plants was significantly higher than the permissible level of cadmium (0.03 mg/kg) for lettuce.