Cadmium stress in rice plants: The effect of cadmium on seed germination and seedling growth of rice plant (Oryza sativa L.)

摘要

Cadmium (Cd) non-essential, but toxic, element for animals and plants is frequently present in paddy fields. Oryza sativa L., a staple food for at least thehalf of world population, also aquatic plants are known to accumulate heavymetals, easily absorbs Cd by the root, and in this organ the pollutants evokeconsistent damages and reducing the root system. In this study the effects ofdifferent cadmium chloride concentrations (0 ,15, 25, 35, 45 and 55 ?M) onsome physiological and biochemical processes including seed germination,root and shoot fresh and dry weight in rice were investigated. The resultsshowed that after treated, seed germination rate was less affected, but rootgrowth was restrained evidently. It affected the subsequent growth rate inthese plants. Higher cadmium concentrations specially at 45 and 55 ?M reduced plant growth significantly. Leaf chlorosis, wilting and leaf abscissionwere observed in plants treated with cadmium. Also Cd treatment reducedthe germination percentage 6.9, root and shoots length 68.9 and 85.6,respectively. The decrease of 42.3 in fresh weight was noticed following thetreatment with 45, and 55 ?M cadmium doses compared with control treatment, respectively.Based on the results we concluded that, these traits of riceplant are seriously affected by Cd treatment and also these are symptoms oftoxicity of Cd element. Our results demonstrate that Cd affect rice root system,by interfering with the formation of the roots and their development. Thisresults into an important change in the root system architecture, which maynegatively affect plant survival in highly polluted paddy soils. Therefore, lessamount of reduction in a special genotype is referred to the index of toleranceto Cd. Finally, in the metal contaminated areas, further research is needed todetermine different levels of metals in the environment and various parts ofthe plants. Having in mind the value of this crop as a food all over the world,the consequences of the reactivity of its root system to these pollutants is veryimportant for evaluating possible economic losses, and for executing repairstrategies.