Cadmium uptake and subcellular distribution in plants of Lactuca sp. Cd–Mn interaction

Cd uptake and subcellular distribution in (Lactuca sativa cv. Grandes Lagos) was studied. In vivo and in vitro experiments were carried out to study Cd effect on Mn uptake and subcellular distribution. Lettuce plants were grown in hydroponics with nutrient solutions containing 0.1 and 1.0 mg Cd l−1 in a greenhouse (in vivo experiments). Also, Cd was directly infiltrated on lettuce leaves in in vitro studies (0.5 and 1 mg Cd l−1), to minimize absorption and transport processes. Root and shoots were sampled after 16 days of exposure to the Cd solutions. Cd, Mn and other micronutrients were assessed in the different parts of the plant sampled and in the subcellular fractions obtained after wet mineralization, using A.A. spectrophotometry. Results show that Cd was accumulated in leaves mainly in cell wall fraction (64%) and this accumulation was fairly independent of Cd level in nutrient solution. The lowest Cd concentration (12–14%) was found in chloroplasts for both Cd levels tested. The increase in Cd concentration in the external medium caused an increase in Mn uptake and translocation to the shoots of lettuce plants, in contrast to the behavior of the other essential micronutrients, and an increase in Mn content in the chloroplasts, suggesting an interaction between Cd and Mn at the chloroplast level.