The Study Of Toxicological Effects Of Copper, Cadmium And Manganese On Naked Oat

This study examined the toxicity of Cu2+, Cd2+and Mn2+on the seedlings of naked oat (Avena nuda) cultured in laboratory. Eight toxicological indicators were tested after the exposure to the metals, and allozyme analysis was performed for CdCl2 exposure. The results are summarized as follows.The Cu2+ at low concentration strengthened the germination rate, seedling height and chlorophyll synthesis. However, when the Cu2+ exposure exceeded the threshold concentration (4mg/L) the inhibiting effects was observed. At higher concentration, Cu2+>4mg/L significantly inhibited the root growth and activity. At 2-10 mg/L, Cu2+induced the increase of malondialdehyde, soluble saccharide in naked oat seedlings. The bioaccumulation was observed at Cu2+ 0-8mg/L, beyond which the two indicators remained stable. The quadratic curve showed satisfactory goodness-of-fit of Cu2+exposure concentration to the indicators of malondialdehyde, soluble saccharide, root activity and bioaccumulation.Cd2+demonstrated significant inhibition to germination. The main root length and malondialdehyde were inhibited in gradient at Cd2+below 50mg/L, beyond which the inhibition remained stable. The Cd2+imposed increasing inhibitive effects on root activity at rising concentrations. The positive correlation was observed between Cd2+concentration (<50mg/L) and the malondialdehyde and soluble saccharide contents. However, the two indicators remained relatively constant when the Cd2+exposure was high than<50mg/L. In contrast, cadmium 20～100 mg/L negatively correlated to the root activity. The naked oat seedling demonstrated Cd2+ bioaccumulation at 0-50mg/L.At lower Mn2+concentration (<15mg/L) the stimulating effects was observed for germination rate, main root length, seedling height, root activity and chlorophyll-a. While exceeding the threshold of 15mg/L the Mn2+exposure showed inhibitive effects on the indicators as listed above. However, the Mn2+ inhibited the chlorophyll-b even at all concentrations (0～50 mg/L). The malondialdehyde or soluble saccharide showed positive correlation to Mn2+ at 0～15mg/L, beyond which the two indicators remained stable. The naked oat seedlings showed bioaccumulation of Mn2+ at 15mg/L or lower, beyond which no further bioaccumulation was observed. The Mn2+ exposure concentration verses total chlorophyll, soluble saccharide and Mn2+ accumulation demonstrated the quadratic relationship.Under the stress of CdCl2, the six pgi genotypes of naked oat showed significant difference in the contents of chlorophyll-b, malondialdehyde and the cadmium accumulation. The pgi-AC had significantly higer values in the three indicators, especially in comparsion to those of individuals with pgi-B allele. The pgi-C is likely to be related to the naked oat’s resistance to environmental cadmium. The results provide the data for phytoremediation of soil contamination.