INFLUENCE OF CADMIUM ON THE ULTRASTRUCTURE OF DEVELOPING CHLOROPLASTS IN SOYBEAN AND CORN

The influence of cadmium on the ultrastructure of developing chloroplasts in soybean and corn was evaluated by transmission electron microscopy. Soybean and corn plants were grown in the dark in Hoagland's solution containing 30, 50 and 100 μM final concentrations of cadmium chloride. After 48 hr in the dark, the plants were exposed to continuous light for 48 hr. The 100 μM treatment group in soybean showed reddish-brown discoloration and wilting of leaves and growth retardation after 48 hr of light. Leaf samples for electron microscopy were taken in the dark and after 12, 24, and 48 hr of exposure to light. Plastids in the 100 μM treatment group of soybeans exhibited a number of defects in their developmental pathway. The etioplasts of dark grown plants failed to develop a prolamellar body. Plastid development was also retarded in the 100μM treatment group. After 48 hr of exposure to light, severe disruption of grana was observed; thylakoids were widely and irregularly spaced. Soybean in other cadmium concentrations showed no disruption in the chloroplast developmental pathway. The corn showed no ultrastructural disruption of chloroplast development in any of the concentration of cadmium tested. © 1990.