Study On Ginseng Root Exudates And Their Autotoxicity

Ginseng (Panax ginseng C. A. Mey.) was known as the king of herb medicines, which grows mainly at Changbai Mountain in the northeast of China. At present, ginseng productions in the market were mainly produced by cultivation. Continuous cropping obstacle will occurred when ginseng continuous planted at the same field, and shown as poor growth, decrease in quality and yield, high incidence of diseases, and even annihilated in the field. Continuous cropping obstacle restricted the good agricultural practice of ginseng severely. In China, many scientists have carried out studies on continuous cropping obstacles of ginseng systematically, and concluded that which was related to the accumulation of soil-borne pathogens, changes in microbial populations, deterioration of soil physicochemical characters, soil fertility etc. But unfortunately, continuously cropping obstacles can not be eliminated through improve soil environment based on impact factors above. The put forward of plant allelopathy provided us anew idea to study continuously cropping obstacle of ginseng. This study wanted to explain continuously cropping obstacle from ginseng root exudates and their autotoxicity, and the results provided theoretic basis to solve ginseng repeated using soils.1. Root exudates of ginseng with different soils and nutrient solutions were collected and identified by GC/MS respectively, and according to the results analyzed by NTFS, we found that organic acid, organic acid esters, acid type and its derivatives, benzene derivatives category, alcohols, naphthalene, furan, cyclic alkanes, ketones, terpenoid, pyridine, pyrimidine, thiophene type, phosphoric acid, etc were included in it. We also found that, soil extracts inhibited the growth of radicle and hypocotyls of ginseng seed, which indicated that autotoxins inhibiting the germination of ginseng seeds were contained in soils cultivated ginseng.2. Based on GC/MS analysis results, benzoic acid, butanedioic acid bis(2-methylpropyl) ester, 1,2-benzenedicarboxylic acid bis(2-methylpropyl) ester, hexadecanoic acid and 2,2-bis(4-hydroxyphenyl)propane were selected to study their effect on the germination of ginseng seeds, activity of protective enzymes (POD, CAT, PAL) in ginseng root and content of ginsenoside. Furthrermore, continuously cropping obstacle mechanisms of allelochamicals in ginseng were studied. Results indicated that, organic acids, phenolic acids and their esters in ginseng root exudates inhibited the germination of ginseng seeds, decrease the activity of protective enzymes in seedling roots, and have impact on the synthesis of ginsenosides also.