PHYSIOLOGICAL AND ULTRASTRUCTURAL EFFECTS OF CADMIUM ON WHEAT (TRITICUM-AESTIVUM L) LEAVES

The effects of a 7-day exposure of 3-day-old wheat plants to increasin g Cd concentrations are described, with special attention being given to chloroplast ultrastructural changes, chlorophyll fluorescence respo nses, chlorophyll and nutrient concentration changes as well as growth changes of the whole plant. The plants treated with 1 mM Cd showed sy mptoms of heavy metal toxicity. The root, shoot-leaf length and the ro ot, shoot-leaf biomass progressively decreased with increasing Cd in n utrient solution and in 1 mM of Cd an almost complete inhibition of gr owth was found. Shoot-leaf Cd accumulation increased under Cd-treatmen ts, while a Fe, Mg, Ca, and K decline in the above ground parts was ob served. The growth reduction and the inhibition of chlorophyll content and photosynthesis observed in the upper plant parts seemed principal ly due to indirect Cd effects on the content of essential nutrients. C admium treatment was shown to damage the structure of chloroplasts, as manifested by the disturbed shape and the dilation of the thylakoid m embranes. These ultrastructural changes suggest that Cd probably induc ed premature senescence.