Physiological and ultrastructural effects of cadmium on wheat (Triticum aestivum L.) leaves.

The effects of a 7-day exposure of 3-day-old wheat plantsto increasing Cd concentrations are described, with special attention beinggiven to chloroplast ultrastructural changes, chlorophyll fluorescenceresponses, chlorophyll and nutrient concentration changes as well as growthchanges of the whole plant. The plants treated with 1 mM Cd showed symptomsof heavy metal toxicity. The root, shoot-leaf length and the root, shoot-leafbiomass progressively decreased with increasing Cd in nutrient solution andin 1 mM of Cd an almost complete inhibition of growth was found. Shoot-leafCd accumulation increased under Cd-treatments, while a Fe, Mg, Ca, and Kdecline in the above ground parts was observed. The growth reduction and theinhibition of chlorophyll content and photosynthesis observed in the upperplant parts seemed principally due to indirect Cd effects on the content ofessential nutrients. Cadmium treatment was shown to damage the structure ofchloroplasts, as manifested by the disturbed shape and the dilation of thethylakoid membranes. These ultrastructural changes suggest that Cd probablyinduced premature senescence.