| The secondary metabolites of plants can exert influence on other plants.This plant allelopathy performance is widespread in nature,such as continuous cropping obstacles and invasion of exotic plants.Poplar is one of the important tree species for greening and timber due to its fast growth and strong adaptability.Understanding the allelochemical composition of poplar,allelopathy effect and molecular mechanism are of great guiding significance for planting management of poplar varieties and mixed application with other plant varieties..In this study,the allelopathic components from leaves and roots of three poplar variety 84K,TC1521 which belong to Leuce and Populus euphratica were analyzed by GC-MS.Further evaluation of the allelopathic effect and dissection of the formation mechanism of the main allelopathic components were performed.The main results are as follows:(1)Allelopathic effect of different poplar varieties on tall fescueThe leaf aqueous extracts of poplar varieties showed inhibitory effect on the seed germination of tall fescue,including the decreased germination rate,germination energy,germination index and vigor index with the increase of concentration.The overall performance of seedlings growth was advanced at low concentration of aqueous extracts and inhibited at high concentration.Of them,the concentration of 84K aqueous extract below 5 mg/mL on the root length,below 50 mg/mL on the seedling length,and the concentration of,TC 1521 below 35 mg/mL aqueous extract on the seeding growth showed the positive effect on tall fescue plants,while the other concentrations of poplar leave aqueous extracts displayed negative effect on root length,seedling length and fresh weight of tall fescue plants.The allelopathic effect on seed germination and seedling growth of tall fescue plants by poplar root extracts also displayed typically as advance at low concentration and inhibit at high concentration,while the allelopathic effect was different by the same concentration of samples from different poplar varieties.For example,the seed germination index of tall fescue performed the best just at 35mg/ml of the root extract of 84K,5mg/ml of TC1521 and Populus euphratica.The growth index of tall fescue seedlings performd the best at 5mg/ml of the leaf extract of 84K and TC1521,and 20mg/ml of Populus euphratica.Totally,the average sensitivity index of tall fescue on poplar leave aqueous extracts was ranged in absolute value as Populus euphratica(0.5393)>TC1521(0.4255)>84K(0.3241),while that on poplar root aqueous extracts was ranged as 84K(0.1 817)>TC1521(0.0754)>Populus euphratica(0.0389).(2)The poplar allelopathic componentsThe allelochemicals of roots and leaves of three poplar varieties were determined by GC-MS,and percentage of each substance in the extracts was calculated by the method of area normalization.The results show that the type and content of allelochemicals in the poplar leaves and roots are various,the leaf samples contain more allelochemicals such as salicylic acid related of salicyl alcohol,salicylaldehyde,benzyl alcohol,benzoic acid,cinnamic acid,and some others of alkanes,phenol,benzoic acid and their derivatives,water-soluble organic acids,aliphatic aldehydes,ketones,and phenols.However,the root samples mainly contain some alkanes and esters with a small amount of compounds relateds to salicylic acid,The same tissure or organ from different poplar variety contains different type and content of allelochemicals.The leaf samples form three poplar varieties all contained 11 components such as salicyl alcohol,catechol,cis-1,2-cyclohexanediol and salicin,while 84K,TC1521 and Populus euphratica contains 15,5 and 14 kinds of unique components,respectively.The root samples from three poplar varieties all contain 6 components such as 1,1-diethoxy-3-methylbutane,2,4-di-tert-butylphenol,heptadecane,and hexadecane,while 84K,TC1521 and Populus euphratica contains 10,11 and 13 kinds of unique components,respectively.Totally,84K and TC1521 had the similar allelochemicals but a little different from that of Populus euphratica whether in leaves or roots.(3)Allelochemicals related genes in the poplar salicin metabolismThe main allelochemicals in poplar are salicin metabolism related products.In order to dissect the molecular mechanism of these allelochemicals formation,the 84K seedlings were treated with benzaldehyde,the upstream substance in the salicin metabolism pathway.Allelopathic analysis by GC-MS showed the content of salicyl alcohol and benzyl alcohol increased but salicylaldehyde,benzoic acid and salicin decreased in the leaves.Transcriptome analysis showed that 3874 DEGs were identified by benzaldehyde treatment,including 1689 up-regulated genes and 2185 down-regulated genes.Of them,617 genes were involved in the salicin metabolism pathways,including L-phenylalanine metabolism,acetyl-CoA metabolism,cinnamic acid metabolism,benzoic acid metabolism,phenylpropanoid metabolism,salicylic acid metabolic processes,and regulation of salicylic acid metabolism processes.A total of 755 DEGs were enriched into 120 KEGG pathways,of which phenylpropanoid biosynthcsis(ko00940)enriched 32 DEGs with 15 up-regulated genes and 17 down-regulated genes.RT-PCR analysis showed that the expression of the gene ALDH2B4,ALDH2B7,ALDH7B5,SAGTase,ALDH2C4,BEBT1,BEBT2 was significantly in relation to the benzaldehyde treatment and salicin metabolites,indicating the pertormance of these genes is of great significance to the allelopathic effect of poplar. |
PDF Full Text Request