Ultrastructural changes of radish leaf exposed to cadmium

Cadmium (Cd2+) is one of the most toxic heavy metal pollutants in nature. Mesophyll cells from the leaf of radish seedlings exposed to 0.25 and 1.0 mM of CdCl2 during 24 h exhibited structural changes of chloroplasts, mitochondria and nuclei when compared to non-treated control plants. Chloroplasts from Cd2+-exposed samples exhibited changes in the organelle shape, an increase in the stroma volume and a deposition of electron-dense material in the double membrane. The changes in the chloroplast membranes were not very drastic, however and reorganization of the thylakoids and stroma was observed. In contrast, the breakdown of the nuclear envelope of the plant cells treated with Cd2+ was very clear. The accumulation of electron-dense granules was also observed in mitochondria. No alterations were observed in the vacuoles of radish seedlings grown at different Cd2+ concentrations for the periods tested.