Physiological responses of Allium cepa var. agrogarum L. plants to Cadmium stress

This study aimed to determine the effects of differentCd concentrations (0, 1, 10, 100, and 300 μM CdCl2) on Alliumplantlets. To achieve this goal, we examined the (1) dynamics of Cd2+flux in the rhizosphere, (2) partitioning of Cd between roots andleaves, (3) formation of reactive oxygen species (ROS), (4) levels ofH2O2 and chlorophyll, and (5) translocation of several macro- andmicronutrients. A strong net Cd2+ influx was observed in the rootapex after exposure to 100 μM Cd for 24 h. Exposure to either 1 or10 μM Cd for 96 h presented no evident influence on root growth.However, treatments with 100 to 300 μM Cd for 72 h significantlyinhibited root growth. ROS levels increased in roots and leaves withincreasing Cd concentrations. The concentration of photosyntheticpigments, except for carotenoids on day 4, increased with increasingCd concentrations and treatment duration. Cd accumulationdecreased photosynthetic carbon assimilation but exerted no effectson diurnal patterns. Cd accumulated in roots and leaves, but a largercontent was detected on roots than on leaves. Several macro- andmicronutrients showed tissue- and concentration-specific responsesto Cd.