Effects Of Organic Acids On The Growth Of Rape Under Cadmium Stress

With the development of industry modernization, urban civilization and agriculture modernization, the release of heavy metals into the environment has been accelerating annually. We regard cadmium as one of the most pernicious heavy metals, because of the mobility and the toxicity. Up to now, researches on heavy metals are mainly concentrated on the appraisal of environment and the biological effectiveness. We haven't got an optimal way that can alleviate the heavy metal stress. The organic acids exist in the soil and root exudates generally. They affect the existence form of heavy metals in solution. Now there are many domestic and foreign experts making efforts in searching the mutual function of organic acids and heavy metals and studying the effects of organic acids on the growth of plants under heavy metals stress. However, reports about the effects of organic acids on the growth of rape under cadmium stress are rarely. The resources of rape plant in our country are extremely rich. It is one of the main winter plants in our country. So researches on effects of low-molecular-weight organic acids on the growth of rape under cadmium stress have the vital significance. This study concentrated on the correlation of organic acids and cadmium.Cadmium adsorption-desorption, cadmium movement and transformation in soil-water-plant system, Cd forms and bio-availability were influenced by the interaction between low-molecular-weight organic acid with cadmium in soil. A review is given on recent advances in the study of interaction of organic acid and cadmium, the effect of organic acid on cadmium bioavailability and the toxicity, and existing problems in the recent studies and developing prospects in the future. Through pot cultivation experiments, effects of low-molecular-weight organic acids (tartaric acid, citric acid and oxaltc acid) on the growth of rape under cadmium stress were studied. The results showed that at the low concentration of three organic acids (0-0.5mmol·kg^-1) the dry weight of plant were increased evidently and the concentration of chlorophyll were increased by 65.3%(P < 0.05), 62.9%(P < 0.05) and 43.8%(P < 0.05) respectively, the activities of protective enzyme (SOD, CAT and POD) were enhanced, and the content of MDA and permeability of cell membrane were decreased. However, with increasing concentration of organic acids (0.5-1mmol·kg^-1), the amelioration capability on cadmium toxicity of tartaric acid enhanced and the content of MDA and permeability of cell membrance were reduced by 66.9%(P<0.05) and 18.5%(P>0.05), close to CK group level while citric acid and oxalic acid are reduced. The sequence of the ameliorating effect of three organic acids was: tartaric acid >citric acid>oxaltc acid.