Yet if DnaB can be loaded at arrested RF by DnaC2 at non-permissive temperature, why cannot DnaB be loaded at oriC by DnaC2 during the initiation of replication? The fact that different partners are involved in the recognition of the Ginkgolide-C helicase complex is most certainly part of the answer. During replication initiation at oriC, the replicative helicase complex interacts directly with DnaA, while the replicative helicase is presented to a complex composed of primosomal proteins during the reactivation of the RF. It is tempting to speculate that the aptitude of the DnaC2 mutant protein to load the replicative helicase at non permissive temperature reflects indirectly a property acquired by the helicase loader through evolution. While RF reactivation is vital for the cell and has to be ensured by any means, the blockage of the loading of the replicative helicase during replication initiation is not deleterious and may in addition to the already known activities regulating this stage bring an additional level of control for the cell to verify that the conditions are appropriate to initiate replication of the chromosome. Thus, it is possible that structural peculiarities of the primosomal complex, specific interactions between the primosomal complex and the helicase complex, or even an as yet unknown additional factor, facilitate specifically the loading of the helicase during RF reactivation. Rehmannia is in the Scrophulariaceae family and is one of the most common and Demethylzeylasteral important medicinal herbal plants. It is perennial and its fresh or dried tuberous roots are used as a high demand traditional medicinal ingredient for hematologic conditions, sedation, insomnia and diabetes. Its commercial cultivation has been practiced for almost 1500 years. However, the consecutively monocultured plants are prone to severe diseases resulting in reduced biomass, especially the tuberous products. To maintain the cultivation, the farmers commonly limited the cultivation on a same plot once every eight years. Therefore, less desirable areas outside Jiaozuo had to be used for the planting with decreased tuber yields and lower product quality. The autotoxicity issue has attracted much attention. Autotoxicity is the phenomenon whereby mature plants inhibit the growth of their own seedlings through the release of autotoxic chemicals. It has been found to exist in various crops, such as greenhouse crops, fruits, forage, horticultural and medicinal plants. Several groups of chemicals have been implicated in autotoxicity, including terpenoids, phenolics, steroids, alkaloids, and cyanogenic glycosides. Recently, autotoxicity in Rehmannia has been reported especially in relation to the compounds derived from the root exudates. However, to date, the degradation of fibrous roots and its products had not been studied, and the mechanism of autotoxicity in Rehmannia remains unknown. This study aims to identify substances that contribute directly to Rehmannia autotoxicity. A number of potentially autotoxic compounds from the fibrous roots were isolated and characterized. The inhibitory effect of these compounds on seedling growth was observed. Furthermore, the concentration of these bioactive compounds in the top soil collected from one-year cultivated and two-year consecutively moncultured Rehmannia fields was determined. Our results demonstrate that the compounds isolated from ethyl acetate-soluble extracts of Rehmannia fibrous roots had the most auto-inhibitory effects on the seedling growth. Among them, the 7 phenolic compounds and 2 aliphatic acids selected for testing the inhibition effects showed a significant suppressive function on the seedling growth. The inhibitory effects were somewhat related to the concentration of the autotoxins.