Effects of heavy metal exposure on the morphological and microscopical characteristics of paddy plant

摘要

The objective of the study was to determine the effects of heavy metal exposure on the morphology and anatomy of paddy plant (Otyza sativa L.). Paddy plants were treated with single and combined close of Cd and Pb (5, 10, 15, 20 and 25 ppm) at 35days after germination. The results showed leaf chlorosis, decrease in number of roots and shoot height under both single and combined treatment. Heavy metal content in paddy was in the order of root>stem>grain>leaf and was highest at reproductive stage. A positive correlation was obtained between Cd, Pb and Cd-Pb concentrations in paddy plant parts with the concentrations of these metals in the soil. Scanning Electron Microscopic studies showed changes in the microscopic features due to accumulation of heavy metal and these included cell degeneration and thickening of cell walls, as well as increase in the number of treacherous elements in vascular cylinder and as residue in cells. Light microscope studies showed that Cd exposure caused dark deposits in the endodermal cells and vascular cylinder, as well as rupturing of parenchyma tissue. Results of the study indicated that paddy plants seemed to have some degree of tolerance to heavy metals.