| Cunninghamia lanceolata is one of the most important timber species in the south of China.During the planting process of Cunninghamia lanceolata,phenolic acids and other allelochemicals will be released,which will have an allelopathy effect on Cunninghamia lanceolata or other mixed species.It is an effective way to solve the problem of Cunninghamia lanceolata pure forest continuous cropping by utilizing the shade-requiring characteristics of medicinal plants to develop large-scale plantation of medicinal materials.Sarcandra glabra is a kind of perennial plant with great medicinal value.Because of the shade-endurance,it is widely planted under the Cunninghamia lanceolata forest and has significant economic benefits.Due to the widespread existence of allelopathy among different plants,the study on the mechanism of allelopathy of Cunninghamia lanceolata on Sarcandra glabra seedlings can provide data reference for planting Sarcandra glabra under Cunninghamia lanceolata forest,and guide production practice by allelopathy among plants.Four allelochemicals(p-hydroxybenzoic acid,ferulic acid,vanillic acid and gallic acid)were used as the treatment reagents in this experiment,and four concentrations(20 mg/L,40 mg/L,60 mg/L,80 mg/L)were set respectively,expressed in D1,D2,D3,D4,A1,A2,A3,A4,X1,X2,X3,X4,M1,M2,M3 and M4 respectively.The effects of allelochemicals on the growth,physiological activity,nutrient absorption and accumulation of secondary metabolites of Sarcandra glabra seedlings were studied with clear water as control(CK).The main results are as follows:1.Different allelochemicals had different effects on the growth of Sarcandra glabra seedlings.The height increment,ground diameter increment and biomass of Sarcandra glabra seedlings in A1 treatment reached the maximum,and the number of clumps in D2 treatment was the best.In general,A1 treatment had the best effect on the growth of Sarcandra glabra seedlings.2.The activity of phenylalanine ammonia lyase and the content of soluble amino acids increased first and then decreased with the increase of the concentration of allelochemicals.The activity of phenylalanine ammonia lyase in leaves was the highest in treatment A2,and it was the most obvious that treatment D2 promoted the activity of phenylalanine ammonia lyase in roots.Under the treatment of D4 and X4,the soluble amino acids in leaves and roots of Sarcandra glabra decreased significantly.The content of reducing sugar increased with the increase of allelochemicals concentration,and the content of reducing sugar in leaves and roots was the highest in X4 treatment.The highest content of soluble protein in leaves and roots was X3 and M3 respectively,which was beneficial to improve the osmotic regulation ability of plant cells.3.The low concentration of allelochemicals was conducive to the accumulation of auxin,but with the increase of allelochemicals concentration,the auxin content tended to decrease.A1 treatment could effectively promote the accumulation of auxin in leaves and roots of Sarcandra glabra.The higher the concentration of allelochemicals was,the better the synthesis of abscisic acid would be,and the maximum value would be reached at the concentration of 80mg/L.With the increase of allelochemicals concentration,gibberellin content first increased and then decreased slowly.The highest gibberellin content was A2 in leaves and roots.Different concentrations of allelochemicals affected the content of zeatin nucleoside.The general trend was that the content of zeatin nucleoside increased first and then decreased with the increase of allelochemicals concentration,but there was no significant difference with CK treatment.4.The total chlorophyll content of A1 and X2 treatments was higher than that of 7.2mg/g,which indicated that these two treatments could effectively promote the synthesis of chlorophyll.A1 treatment had the best effects on chlorophyll a,chlorophyll b and carotenoids,and had a significant effect on chlorophyll synthesis.Appropriate amount of allelochemicals was conducive to the increase of Pn,Gs,Tr and the decrease of Ci in the leaves of Sarcandra glabra.A1 treatment could effectively increase the Pn and Gs values of the leaves,while reducing the Ci value.X4 treatment had the highest Ci value,while Pn and Tr were significantly inhibited.The best transpiration rate was M2.D3 treatment significantly improved the Fv/Fm,Fv '/Fm',q P and ETR values of the leafs.With the increase of allelochemicals concentration to 80mg/L,the Fv/Fm,Fv'/Fm',q P,and ETR of leaves decreased significantly.At this time,the NPQ increased significantly.The value of NPQ was the largest in X4 treatment,which was 1.8 times of CK treatment.The value of NPQ in A1 treatment was the lowest.5.Different concentrations of allelochemicals had different effects on the nutrient absorption of different organs.A2 treatment was beneficial to the absorption of N and P elements in leaves,and treatment A1 was the best for the content of K in leaves.M2,A1 and A2 treatment were the highest for the content of N,P and K in stems;X2 treatment significantly increased the content of N and K in roots,and D2 treatment was beneficial to the content of P in roots.X4 treatment significantly inhibited the absorption of N element by coralline,and reduced the content of P and K in leaves and stems.M4 treatment was not conducive to the absorption of K element in leaves,while D4 treatment significantly reduced the content of P and K in roots.D3 treatment promoted the accumulation of Mg elements in all organs,and increased the content of Ca in leaves and stems.D2 treatment was the best way to absorb Ca elements in roots,while X4 treatment was not conducive to the absorption of Ca and Mg elements.A2 treatment was beneficial to the absorption of Fe elements in leaves,stems and roots,while increased the total Cu content in roots;M4 treatment inhibited the absorption of Fe and Cu elements in leaves,stems and roots.The Cu content of leaves and stems of M1 and M2 treatments was the best,which were above 22.00mg/kg.Allelochemicals had little effect on Zn absorption in all organs of Sarcandra glabra seedlings.6.In the experiment,A2 treatment was more beneficial to the accumulation of total flavone content,leaf and stem flavone content and the content of Isofraxidin in Sarcandra glabra,and D2 treatment significantly promoted the accumulation of flavonoids,chlorogenic acid and rosmarinic acid.X4 treatment was not conducive to the accumulation of Isofraxidin and chlorogenic acid.Different concentrations of allelochemicals had little effect on rosmarinic acid.7.Under the action of Cunninghamia lanceolata phenolic acid allelochemicals p-hydroxybenzoic acid,ferulic acid,vanillic acid and gallic acid,various indexes of Sarcandra glabra were changed.The results of sensitivity analysis and principal component analysis showed that vanillic acid treatment inhibited the Allelopathy of Sarcandra glabra was inhibited by vanillic acid treatment,while p-hydroxybenzoic acid,ferulic acid and gallic acid had positive effects on Sarcandra glabra.The order of promoting effect of these four allelochemicals on corals was ferulic acid,p-hydroxybenzoic acid,gallic acid and vanillic acid.The total score of Sarcandra glabra in A2 treatment was higher,which had a positive effect on Sarcandra glabra.According to the comprehensive analysis,ferulic acid in the four allelochemicals was relatively good for the growth status,physiological characteristics and the synthesis of the contents of Sarcandra glabra,and the effect was the best at the concentration of 40 mg/L. |
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