Characteristics of Organic Acids Exudated from Soybean(Glycine max L.)Roots under P Deficiency Stress

Most of the farmlands in the world are lack of P,organic acids exudates from plant roots increase under P deficiency stress.Plants form several adaptability mechanisms to adapt the P deficiency environment.In this study,solution culture and sand culture experiments were conducted to investigate the variation of total and components of organic acids exudates from soybean roots under P deficiency stress.The results showed that different P levels significantly affected organic acids exudating from soybean roots,whether the total or components of organic acids under P deficiency remarkably higher than that in normal P supplying,suggested that P deficiency stress is an important factor induced organic acids exudating from soybean roots.Exudation of organic acids from soybean roots varied with growth stages,which showed firstly increasing and then declining,exudation peak appeared at flowering stage.The components of organic acids from soybean roots were almost the same as in solution culture and sand culture experiment,were mainly as malic acid,citric acid,oxalic acid and tartaric acid,the amount of organic acids exudates from soybean roots in sand culture experiment was 2-3 times as in solution culture experiment.