| Rehmannia glutinosa Libosch is one of China's famous "four huaiyao". Since its root tube contains catalpol, Rehmannia glutinosa glycosides, Rehmannia glutinosa motherwort glycosides and a variety of active ingredient, its dry root can be used to pharmaceutical. In the continuous cropping of Rehmannia glutinos, it shows non-swelling and lots of fibrous roots. It takes 8-10 years to replant Rehmannia glutinos after the first cultivation. This has seriously hampered the development of medicinal herbs.This experiment study with different intervals years's soil of Rehmannia glutinosa, the different growth periods'soil Rehmannia glutinosa,the different type of soil, by HPLC to detect phenolic acids related to allelopathy effect in the soils,in-depth study of the relationship between phenolic acids changes of Rehmannia glutinosa soil and its microecological environment, aims to provide a theoretical basis for reducing autotoxicity and continuous cropping obstacles of Rehmannia glutinosa. The Main findings are as follows:1 AN phenolic acids of soils impact on the growth of Rehmannia glutinosa Rehmannia glutinosa's cropping performance which is not enlarged root tube, more fibrous roots. his study firstly shows that: 4-hydroxybenzoic acid and syringic acid's content of soils of 2 to 8 interval years and dry and fresh root weight and root volume of mid and late expansion of root and harvest period has significantly or very significantly negative correlation relationship, 4-hydroxybenzoic acid and syringic acid's content of soils of 2 to 8 interval years and dry and fresh leaf weight of mid and late expansion of root and elongation period has significantly or very significantly negative correlation relationship; Ferulic acid's content of soils of 2 to 8 interval years and dry and fresh root weight of seedling period has significantly negative correlation relationship; Syringic acid's content of soils of 2 to 8 interval years and each measure indexs of Rehmannia glutinosa has significantly positive correlation relationship.Ferulic acid,coumalic acid, 4-hydroxybenzoic acid's content of soils of 2 to 8 interval years and germination percentage and index of radish's bioassay of concentration of 60%'s aqueous extracts from the soils of Rehmannia glutinosa has significantly positive correlation relationship, Ferulic acid, oumalic acid,4-hydroxybenzoic acid's content of soils of 2 to 8 interval years and elongation of root and stem of radish's bioassay of concentration of 60%,24%,12%'s aqueous extracts from the soils of Rehmannia glutinosa has significantly or very significantly positive correlation relationship; Ferulic acid, coumalic acid,4-hydroxybenzoic acid's content of soils of 2 to 8 interval years and germination percentage and index of lettute's bioassay of concentration of 24%'s aqueous extracts from the soils of Rehmannia glutinosa has significantly positive correlation relationship, Ferulic acid, coumalic acid,4-hydroxybenzoic acid's content of soils of 2 to 8 interval years and elongation of root and stem of lettute's bioassay of concentration of 60%,24%,12%'s aqueous extracts from the soils of Rehmannia glutinosa has significantly or very significantly positive correlation relationship.Study on added phenolic acids exogenous to Rehmannia glutinosa, ALL 5 phenolic acids have inhibition of Rehmannia glutinosa under 3 concentrations by contrast the CK of normal rotation and successive cropping, but the inhibition of each them did not exceed the CK of successive cropping. Among them, the strongest acid's ability to inhibit Rehmannia glutinosa growth is syringic acid,dry and fresh root weight of Rehmannia glutinosa is 51%,54% and 106%,115% of he CK of normal rotation and successive cropping Rehmannia glutinosa under the conditions of the C concentration of syringic acid. The study also found that adding exogenous acid concentration and its effect on growth inhibition Rehmannia glutinosa capacity not related, of which 4-hydroxybenzoic acid, coumalic acid on the inhibitory effect of Rehmannia glutinosa and its concentration has no relationship. Low concentration of syringic acid and ferulic acid on Rehmannia glutinosa strong inhibition of growth; high concentration of vanillic acid to strong growth inhibition Rehmannia glutinosa. Considering field and laboratory bioassay results, first proved phenolic acids in soil of Rehmannia glutinosa are interactivly affect the growth of Rehmannia glutinosa, inhibit expansion of Rehmannia glutinosa's root tube.2 Seedling and elongation period of Rehmannia glutinosa is the critical period of Rehmannia glutinosa's autotoxicityField morphology data analysis of replanted Rehmannia glutinosa under different types of soil texture show that, from the beginning of seeding period, content of phenolic acids in soil and the morphology indexs of Rehmannia glutinosa has significantly or very significantly correlation, taking into account the lag autotoxicity to Rehmannia glutinosa of root exudates of Rehmannia glutinosa(or the result of microbial transformation),the seedling and elongation period should be the key period of all time.Analysis of bioassay results of different types of soil texture extraction showed that both the radish or lettuce,from the entire reproductive period, seeds radicle growth inhibition of various concentrations of extract of the soils of normal rotation and successive cropping Rehmannia glutinosa's pre and mid periods is the stronggest,inhibition of seed radicle growth in this period of successive cropping Rehmannia glutinosa under various concentrations of soil extract is very strong,this growth in line with the field.Study phenolic acids in soil of Rehmannia glutinosa dynamic changes can be found, sowing period successive cropping soil's content of 4-hydroxybenzoic acid is higher than normal rotation soil,before enlargement of Rehmannia glutinosa,successive cropping soil's content of,ferulic acid, coumalic acid, syringic acidis higher than normal rotation soil,in which the content of ferulic acid in the successive cropping soil is 2 to 5 times than normal rotation soil, and in this period, leaf and root weight of successive cropping Rehmannia glutinosa well below the normal rotation Rehmannia glutinosa,and they have a Significant negative correlation,it can be speculated that the ferulic acid,coumalic acid,syringic acid and 4-hydroxybenzoic acid in the successive cropping Rehmannia glutinosa inhibit the growth of pre Rehmannia glutinosa, in which a strong inhibitory effect of ferulic acid.Study the different levels of successive cropping soil's inhibitory effect to replanted Rehmannia glutinosa,successive cropping soil for 1 month the weakest inhibitory effect on Rehmannia glutinosa,successive cropping soil for 6 month the strongest inhibitory effect on Rehmannia glutinosa,as a word,the effect of autotoxicity gradually strengthen as time added.2 month successive cropping soil and 3 month successive cropping soil the greatest difference between the inhibitory effect, which the root of fresh, dry weight is 78.4%,80.0% for the former,it can be concluded that in July-August is the strongest effect of autotoxicity Rehmannia glutinosa,this conclusion coincides with field experiment data.Considering the different test results,it's the first time prove allelopathy of Rehmannia glutinosa occurred during the seedling and elongation period,this period an phenolic acids in soil play a key role for the continuous cropping obstacles,incomplete nutrition growth will lead to problems in reproductive growth,thus further affecting the expansion of Rehmannia glutinosa root tube.3 Effects of phenolic acids on the growth inhibition mechanism Analysis of Rehmannia glutinosaContent of vailable K,available N,total N and organic matter in Rehmannia glutinosa soil of interval of 2 years of soil of interval of 8 years is 1.79 times, 1.19 times, 1.05 times and 1.08 times,while Content of vailable P in Rehmannia glutinosa soil of interval of 8 years of soil of interval of 2 years is 2.94 times, which reports such as Chen Longchi the same conclusion.Therefore,phenolic acids may be inferred that the result of Rehmannia glutinosa soil nutrient to change and then have a impact of growth and development of Rehmannia glutinosa. C-N balance hypothesis that while nutritional stress, the rate of plant growth has slowed, compared with little change in photosynthesis, plants will have accumulated more C,H elements, in vivo C/N increases, so phenolic acids such as C-based allelochemicals will increase.According to this hypothesis,the short period between replanted Rehmannia glutinosa soil,due to nutritional stress,causes allelochemicals such as phenolic acids increase,thus affecting the growth of Rehmannia glutinosa.Therefore,soil nutrition and phenolic acids effects with each other,with the growth and development Rehmannia glutinosa formed an organic whole.Study show that vanillic acid is a sex hormone of heterodera glycines,and its analogues syringic acid in the greenhouse also significantly affect the density of heterodera glycines,the existence of the syringic acid in the soil and vanillic acid in the decomposition productsmay contribute to the cyst nematode reproduction,so that against the nematode density thresholds.Nematode is a very serious pest to Rehmannia glutinosa,root-knot nematode disease once infected,it will not lead to expansion of Rehmannia glutinosa root tube,and it is very difficult to cure, is Rehmannia glutinosa the "cancer",we can test it is clear found the incidence of root-knot nematode disease successive cropping Rehmannia glutinosa is much higher than the normal rotation Rehmannia glutinosa,it can be assumed successive phenolic acids in cropping soil of Rehmannia glutinosa arising from the interaction of the incidence of root-knot nematode disease.Studies have shown that the potential of plant allelopathy is the release of plant allelochemicals in all the results of the combined effects. Einhellig report that almost all plants,the potential of allelopathy are two kinds or more than two kinds of compounds caused by interaction. In the field environment,the plant released by the concentration of chemical substances are generally lower than the inhibitory effect of initial concentration, therefore, high levels of phenolic acids absolutely concentration do not necessarily represent the strong inhibitory effect to root tube of Rehmannia glutinosa, but the concentration of higher phenolic acids content may affect the growth of Rehmannia glutinosa, resulting in the leaf growth of intervals of 2 interval years of soil replanted Rehmannia glutinosa is weaker than 8 interval years of soil replanted Rehmannia glutinosa's, resulting in decline of manufacturing in photosynthetic capacity of the product of Rehmannia glutinosa leaf,the source of the insufficient supply of the library,hampered enlargement of successive cropping Rehmannia glutinosa root tube.The study found two types of phenolic acids in low concentration levels,their role is to increase mutual;the effect was antagonism if the concentration level of material is higher. we can see that because the growth of Rehmannia glutinosa process, mainly the leaves growth and development early, the latter is mainly the expansion of root and dry matter accumulation. Therefore on the one hand,the role of acid of early stage of growth of successive cropping of Rehmannia glutinosa through the effects of IAA and elongation of mitosis of root cells and thus the impact of successive cropping Rehmannia glutinosa root tube growth and absorption,on the other hand,damage to photosynthesis and resulting in Rehmannia glutinosa leaves manufacturers cropping decline in the ability of photosynthate.With the growth center transfer,the differentiation and development of root of successive cropping Rehmannia glutinosa start since the mid-late period.During this period the changes in acid concentration began to decline but the root of successive cropping Rehmannia glutinosa inhibit has continued to receive. Based on the above findings,the lower the acid concentration of acid is likely to lead to enhancement of the interaction effect,thus inhibiting the successive cropping Rehmannia glutinosa root enlargement.Test in the detection of five kinds of an phenolic acids are phenylpropanoid compounds of styrene-acrylic acid,the chemical structure very similar to the role of the membrane of the root system is basically the same site.Five kinds of phenolic acids as a result of the role of characteristics of different cell-to-ground Rehmannia glutinosa root is also a slight difference between the force, is more competitive acid tend to capture the role of more than one site (or at least closer to interfere in other sites).When the root cell membrane of Rehmannia glutinosa gathered around more than the total number of elements of the open site,the effect is enhanced between the phenolic acids(in the lower concentration of a substance). Conversely, if the total number of elements are more than cell sites, the more competitive acid will be able to capture the role of more sites, and less able to compete to capture the acid sites on the small, two types of phenolic acidss as a result of this effect has not been fully reflected (in the higher concentration of a substance), give rise to "antagonism."Add exogenous phenolic acids to Rehmannia glutinosa and to study changes in their growth to show that the absolute phenolic acids concentration and its inhibition of root enlargement has no significant correlation, the key solution to continuous cropping obstacles of Rehmannia glutinosa is the relative concentrations of these phenolic acids, specific to a single variety of phenolic acids and the role of the critical concentration of each other, but further in-depth study is needed.To sum up, the interaction between phenolic acids, multifaceted role in the rhizosphere of Rehmannia glutinosa microecological environment, caused by the change in order to direct and indirect effects of the expansion of Rehmannia glutinosa root tube.
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