Effects And Mechanism Of Stachyose On Rehmannia's Continuous Cropping Obstacle

Rehmannia glutinosa Libosch.is a perennial herb belonging to the genus Scrophulariaceae and one of the traditional Chinese herbal medicines.The genuine producing area of Rehmannia is located in Wen County,Xiuwu,Wuzhi,Meng County and other places in Jiaozuo City,Henan Province.The quality of Rehmannia in genuine producing area is excellent,and the effective medicinal ingredients containing sterols are high.However,there is a serious problem of continuous cropping obstacles in the process of planting Rehmannia.The land planted Rehmannia after one-year-old requires 8 to 10 years of time before it can be planted again,severely limiting the sustainable development of the Rehmannia industry.In this paper,To explore the factors that resultig the continuous cropping obstacles of Rehmannia glutinosa.Arabidopsis thaliana DR5::GUS was used as a biomaterial for detecting allelopathic substances in the soil that planted Rehmannia glutinosa.The main root length of Arabidopsis seedlings on the 9th day of Arabidopsis thaliana culture was used as an indicator.After two batches of Arabidopsis thaliana bioassay experiments were conducted in different batches of soil from different townships in Wen County,it was found that soil water extracts at intervals of 1 year,2 years,3 years,and 4 years after planting of Rehmannia glutinosa have significant inhibitory effects on the main roots of Arabidopsis seedlings.Among them,the inhibitory effect of soil samples at the interval of 3 years(N3)in Xiangyun Town is the strongest.Since Arabidopsis thaliana seedlings can reflect the difference in soil after different years between planting of Rehmannia,Arabidopsis thaliana DR5::GUS can be used as a reliable bioassay material for detecting allelochemicals of Rehmannia,and N3 Soil samples as materials for the separation of Rehmannia allelochemicals.The blank soil sample CK2 from Xiangyun Town was used as the control group,and the N3 soil sample was used as the experimental group.The substances of the two soil samples were divided into methylene chloride phase,absolute ethanol phase,aqueous phase,and aqueous phase alkali adjustment supernatant and alkaline phase precipitation.The DR5::GUS bioassay experiments were performed on each phase and it was found that the substances that inhibited the elongation of the main roots of Arabidopsis seedlings were supernate after adjusting the alkali in the aqueous phase.After analysis,it was found that the main substance in the supernatant after adjusting the aqueous phase is fulvic acid(FA).FAs of 2 soil samples were extracted and subjected to Arabidopsis bioassay.It was found that FA of N3 soil could significantly inhibit the growth of the main roots of Arabidopsis seedlings.Therefore,the determination of FA in N3 soil samples is a potential allelopathic autotoxic substance that causes continuous cropping disturbance in Rehmannia glutinosa.In order to distinguish the FA in the blank soil samples,the FA of the N3 soil sample was named GFA.Further studies found that stachyose in the tissues of Rehmannia glutinosa participated in the formation of GFA.Fourier Transform Infrared Spectroscopy(FTIR)shows that GFA has 2 more=C-H and-(CH2)n-characteristic peaks than blank soil FA.And through Arabidopsis bioassay experiments and the effect of horseradish peroxidase enzyme activity experiments show that the product of stachyose and commercial FA mixed solution has the same function as GFA,which can inhibit the growth of the main roots of Arabidopsis seedlings and promote horseradish peroxidase degradation of IAA.Finally,it was verified by field experiment that the application of stachyose can result in a significant reduction in the production of Rehmannia.Therefore,the final determination of stachyose is an endogenous factor that causes a continuous cropping disturbance of Rehmannia glutinosa.At the same time,it was found that the auxin polar transport inhibitor triiodobenzoic acid(TIB A)can counteract the inhibition of the main roots of Arabidopsis seedlings caused by GFA,so TIBA can be used as a relieving agent for alleviating continuous cropping disturbance of Rehmannia glutinosa.In addition,by adding yeast capable of degrading stachyose in the soil first crop Rehmannia,the yield of Rehmannia can be improved.It is speculated that Rehmannia may have been affected by allelopathic effects in first cropping,but the effect is not obvious.Because stachyose reacts rapidly with soil FA to produce GFA,and a labile mix of stachyose and commercial FA shows that GFA has good stability and is not easily degraded by microorganisms.Therefore,the addition of yeast in the soil first crop Rehmannia can provide a reliable reference for alleviating the obstacles of continuous cropping of Rehmannia glutinosa.