Contaminated soils and water by heavy metals have posed a serious threat to environment and human health, which can be solved by both physicochemical and biological methods. Phytoremediation has recently become a topic of scientific research and gained much attention as a cost-effective and eco-friendly alternative. Many kinds of hyperaccumulator plants have been applied to deal with heavy metal contaminants such as As, Cd, Pb, Zn and various radionuclides. In recent study, a seedling vigor index (SVI) model, which uses specific hyperaccumulator plants (i.e., sunflower) as test subjects, is proposed to predict the phytotoxicity of heavy metals. However, whether this mathematical model can be commonly used has not been cleared yet. In this study, rapeseeds were treated with Cd, Pb, Ni, Zn to validate the SVI model which was proposed by some scholars previously. The phytotoxicity of heavy metal was evaluated using seed germination test and seedling length measurement. The test shows that germination percentage and seedling length decreased when heavy metal concentration increased. According to the results of regression analysis, heavy metal concentration is linear to germination percentage, root and shoot length, corresponding with SVI model. It can be concluded that the SVI estimation model obtained from sunflowers can also be applied to rapeseeds to describe the relative effects of heavy metal concentration on plants growth and development.. However, further experiments using more hyperaccumulator plants to validate the applicability of the SVI model are necessary.
Rice seedling test was conducted to check the loging tolerance at ripening stage through evaluating the root characters. Thirteen Korean and foreign rice cultivars with direct seeding adaptable or high quality characteristics were grown in a cell pot and under submerged paddy. The root characters and pushing resistance of rice hill were determined at seedling and ripening stage, respectively. The diameter of crown root at the 7th and 8th leaf stages was thicker in lodging tolerance cultivars than those of others and showed significant-positive correlation with both pushing resistance and crown root diameter of mature plants. Also, the tensile strength of crown root at the 7th and 8th leaf stage showed highly positive correlation with the tensile strength of crown root of mature plants. The number of crown root at 7th leaf stage was significant-positively correlated with that of mature plant. The diameter of seminal root was not significantly correlated with the diameter of crown root throughout the whole growth stage. These results indicate that the diameter, tensile strength and number of crown root associated with root lodging tolerance can be detected with the seedling at about 7th or 8th leaf stage, and the seedling test using the cell pot is an useful and practical method to select lodging tolerant cultivars or lines of rice based on root characters, especially diameter of crown root.