Effects Of Heavy Metals On Plant Growth And Different Organic Acids On The Bio-availabilities Of Heavy Metals In Soil

Pot experiments were conducted to study the effects of Cd and Pb on rape (Brassica campestris) in physiology and biochemistry, as well as the accumulation and distribution of Cd and Pb in rape plant. The poison mechanism of Cd and Pb to rape was discussed. The effects of extraneous source organic acids on the bio-availabilities of heavy metals in soil were studied too. The results indicated that:1. Both of Cd and Pb added in soil caused the growth of rape to be blocked and slow, the accumulation of rape biomass to be remarkably suppressed. The injuried symptoms of rape shoot were that the adult rape plant dwarffed, the leaf blade changed thinness and stricture, the chlorosis phenomenon was obvious, and the root system bad developed.2. The contents of chlorophyll, antiscorbutic acid, and nitrate in rape reduced, the proline content increased in rape, and the activity of nitric acid reductase and the vitality of rape root decreased as the amounts of Cd (1 mg/Kg Cd is an exception) or Pb added in soil increased. When Cd and Pb added in soil together, Pb cordinated Cd to perform the effects.3. The plants growed in the soil polluted with heavy metals could alleviate the heavy metal poison by accumulation of proline and reduction of antiscorbutic acid content and so on.4. The contents of Cd and Pb in rape increased as Cd and Pb added in soil increased. When Cd and Pb added in soil together, Cd suppressed the absorption of rape to Pb, but Pb promoted the absorption of rape toCd.5. The extraneous source organic acids promoted the absorption of rape to Pb, but suppressed the rape to the absorption of rape to Cd. The contents of Cd and Pb in second stubble rape were more than that in first stubble rape when soil added with organic acids.