The Study Of Toxicological Effects Of Lead, Zinc And Mercuary On Naked Oat

This thesis examined the toxicological impact of metals lead, zinc and mercury on naked oat (Avena nuda). The seeds were exposed to the Pb2+, Zn2+ or Hg2+ solution and the seedlings were collected for testing 8 indicators including the germination rate, seedling height, main root length, chlorophyll-(a,b), malondialdehyde, soluble saccharide, root activity and metal accumulation. The results are summarized as follows.The Pb2+ at concentration less than 15mg/L stimulated the germination rate, seedling height and main root length. When the Pb2+ concentration was more than 15mg/L the heavy metal increasing inhibited the three growth indicators in gradients. In the Pb2+ exposures at 0-30mg/L the chlorophyll-a level increased and then decreased at the turning point of Pb2+ at 15 mg/L. In contrast the chlorophyll-b kept declining even at the low Pb2+ exposure. The decreasing slope of chlorophyll-b was steeper than that of chlorophyll-a. In the range of Pb2+ at 0-30mg/L the exposure concentration were negatively correlated to root activity, but the positively correlated to the malondialdehyde and soluble saccharide content. Naked oat demonstrated resistance and bioaccumulation to lead exposure. The quadratic curve fitting showed satisfactory goodness-of-fit of Pb2+ exposure concentration verses the indicators of chlorophyll, malondialdehyde, soluble saccharide, root activity and lead accumulation.The Zn2+ at concentration of less than 50mg/L stimulated the seed germination, seedling height and main root length, but the impact turned slightly inhibitive at 50-100mg/L. In Zn2+ exposure of 0～100mg/L the soluble saccharide and chlorophyll-a first increased and then decreased at the turning point of 50mg/L, while the chlorophyll-a kept decreasing. The Zn2+ inhibited chlorophyll-a more than chlorophyll-b. In the same exposure range the increasing Zn2+ concentration corresponded to the increased malondialdehyde level, root activity, and Zn2+ bioaccumulation. The Zn2+ accumulation became gradually stable when the Zn2+ exposure were higher than 50mg/L, below which the naked oat demonstrative satisfactory resistance and accumulation. The quadratic curve fitting showed satisfactory goodness-of-fit between Zn2+ exposure concentration and the indicators of chlorophyll, malondialdehyde, soluble saccharide, root activity and copper accumulation.The Hg2+ showed no significant effects on germination, seedling height and main root length of naked oat when Hg2+ exposure was at less than 1.0mg/L, beyond which significant inhibition was observed. In Hg2+ exposure of 0-5.0mg/L the Hg2+ concentration were negatively correlated to root activity and chlorophyll-(a,b), and decline of chlorophyll-b was steeper than chlorophyll-a. In the same exposure range the increasing Hg2+ concentration corresponded to the increased malondialdehyde level, root activity, and Hg2+ bioaccumulation. The Hg2+accumulation became gradually stable when the Hg2+ exposure were higher than 2.0mg/L. The naked oat showed certain resistance and bioaccumulation to low Hg2+ exposure (<1.0mg/L)..The quadratic curve fitting showed satisfactory goodness-of-fit of Hg2+ exposure concentration verses the indicators of chlorophyll, malondialdehyde, soluble saccharide, root activity and mercury accumulation.This thesis provided basic data on the metal toxicology of naked oat which is commonly cultivated in the Loess Plateau, which might be useful in selecting the crop species for soil remediation in the region.