Physiological effects and uptake of cadmium in Pisum sativum

Germination and elongation of pea radicles were significantly inhibited when Cd was added to the culture solutions. The heavy metal also retarded shoot elongation and leaf development of young seedlings even at a concentration of 1 μg/mL. In addition to chlorosis and leaf wilting, Cd caused severe stem constriction. This observation together with the ultrastructural studies on the vascular system indicated that Cd damaged growth through narrowing of vessel pits and deposition of unknown debris which blocked the water translocation flow. The degree of inhibition on root and shoot growth normally increased with an increase in Cd concentration contained in the culture medium, although mild enhancement of growth was also recorded when Cd was added at a level of 25 ng/L. In all parts of the plants, the amount of Cd uptaken was directly related to the external level of Cd. Despite 70 to 80% of the total Cd accumulated was confined to the root portion, the stem and the leaf appeared to be more severely affected than the root. This may suggest that the root is the most tolerant part which plays a role to sequester Cd from being transported to the upper parts of the plant.