Response Mechanism of Exogenous Organic Acid on Ryegrass Under the Stress of Pb~(2+)

In order to discuss the effect of organic acid exudation from root on the absorption and accumulation of Pb2+ by plant,oxalic acid,glacial acetic acid,malonic acid,tartaric acid and malic acid were added into soil under 500 mg/kg of Pb2+ content.And the content of organic acid was 1,3,5,6,7 mmol/kg.The rhizobox method was used to study the growth and development index of ryegrass,physicochemical properties of soil in rhizosphere and non-rhizosphere and the effect of absorption and accumulation by ryegrass in simulation greenhouse.The results indicated that the exogenous organic acid could improve the dry weight of shoot and root to some extent.The absorption and accumulation effect of Pb2+ by root was greater than shoot.And the activation of heavy metal was increased when added the organic acid.And the organic acid can promote the absorption and accumulation of Pb2+ by plant.The value of pH,Eh and residual quantity of Pb2+ in rhizosphere was less than non-rhizosphere.Tartaric acid,malic acid and malonic acid could promote the absorption and accumulation of Pb2+ by plant,the effect was obvious on shoot,but there were not bad influence on the growth of ryegrass.Glacial acetic acid could increase the activation of heavy metal in soil markedly.