Study On Continuously Cropping Autotoxicity Of Rehmannia Glutinosa Libosch

R. glutinosa Libosch is a perennial officinal of Scrophulariaceae, and it has been cultivated for more than 1500 years. Its root is frequently used as a crude drug in traditional Chinese medicine. Continuously cropping obstacle recorded firstly in Ming dynasty by Lu zhiyi, it is still very serious in the current production. Some reports suggested that root exudates and residues of R. glutinosa remained in soil had an inhibitory effect on its growth in next year. This dissertation showed you preliminary results at the point of view of plant autotoxicity . The results were summarized as follows:1 .The result from the bioassay showed that aqueous extracts and methanol ones all inhibited growth of lettuce seedling and R. glutinosa Libosch, but reverse was true in the cases of petroleum ether , chloroform and ethyl acetate extracts from the herb. This might be attributed to dossage effects of allelochemicals in extracts. The experiment has proved that rhizospheric soil under continuously cropped R. glutinosa Libosch, contains harmful allelochemicals to growth of receptors, its continuously cropped R. glutinosa Libosch.2.The result from the simulation tests of continuously cropping in Lab showed that the growth of treated seedling of R. glutinosa Libosch became weaker, its root activity dropped, the content of chlorophyll in the leaves decreased, membrane permeability increased, antioxidant enzymes of the target plants were inhibited, IAA oxidase activity increased, and phenylalanine ammonia-lyase activity decreased. Meanwhile, the IAA and ZT content decreased obviously, but ABA content increased sharply due to methanol extracts of rhizospheric soil under continuously cropped R. glutinosa Libosch.The results from the experiment suggested that allelochemicals could dramatically influence on the growth and development of R. glutinosa Libosch, consequently resulted in autotoxicity.3.The results of extraction,separation,purification and characterization of allelochemicals by HPLC and ESI-MS showed that rhizospheric soil under continuously cropped R. glutinosa Libosch contained 10mg/g methanol extracts. Its physical properties are white solid, and quite easy to dissolve in water and methanol, and also partially dissolve in ethanol, but are difficult to dissolve in weak polar organic solvents such as acetone etc. Its chemical forms belong to strong polar components. The mass spectra include ten clusters of isotope peaks. This dissertation deduced six constituents that they were intercompared to chemical constituents of R. glutinosa Libosch reported in literature. It contains ferulic acid[3-(4-hydroxy-3-methoxyphenl)], D-Mannitol, 2[4'-hydroxyphenyl]-ethyl hexacosanoate, Acteoside,β-sitosterol, daucosterol etc, but it need further confirm.In summary, it was suggested that R. glutinosa Libosch has produced and accumulated lots of allelochemicals that show a significant inhibitory effect on its growth and development of the target plant to its rhizospheric soil. From the results as mentioned earlier, we made the conclusion that allelochemicals extracted from the rhizospheric soil under continuously cropped R. glutinosa Libosch, could operate directly the negative effect on itself, which inhibited the absorption of the target roots for water and nutrients from soil, and disturbed its growth regulation system, and hindered reaction process of secondary metabolism,in turn led to influenced growth and development of R. glutinosa Libosch. This finding suggested that autotoxicity was a direct cause of the continuously cropping obstacle on R. glutinosa Libosch.