Research On Allelopathy And On The Chemical Composition In Root Exudates Of Ectomycorrhizal Pinus Massoniana Seedlings

Pinus massoniana is the most widely distributed,the highest degree of comprehensive utilization conifer species in south area in our country,having fast-growing,high–yield,well-adapted,drought-resistant,and other excellent features.Furthermore,it is a typical ectotrophic mycorrhiza tree species.Ectotrophic mycorrhiza fungi and plant roots formed hyphae network,enlarged the plant root absorption area,enhanced the vitality of plant root system,changed the micro ecological environment of root,improved the ability of plants to absorb water and nutrition metabolism.The one-year-old seedlings,inoculating ectomycorrhizal fungi and unvaccinated,of P.massoniana were taken as the research objects,the chemical constituents and contents differences of rhizospheric soil were analyzed,by ethanol and methanol for extraction and separation of the constituents and GC-MS,studied the allelopathy effects of root exudates and three kinds of main organic acids allelochemicals on seeds and seedlings of Pinus massoniana.It provides scientific basis and theoretical guidance for mycorrhizal seedlings and the natural renewal of pinus massoniana.The main results are showed as follows: 1.The chemical composition in root exudates of mycorrhizal/non-mycorrhizal seedlings of Pinus massonianaThrough ethanol extraction,varieties of rhizospheric soil extracts from seedlings that inoculated Sl12 and Sl13 were 22 and 23 kinds more than unvaccinated seedlings,respectively,while relative contents are more than 1% were 18 and 16,The acids comprised most of the detected compounds.The soil acids of inoculating Sl12 and Sl13 accounted for 51.20% and 48.80%,respectively,while it was 34.17% in unvaccinated soil extract.Through methanol extraction,varieties of rhizospheric soil extracts from mycorrhizal seedlings were 34 and 32 kinds,respectively,while relative contents are more than 1% were 12 and 9,but it was 23 in unvaccinated one.Acids and Esters comprised most of the detected compounds,The acids of seedlings which inoculated Sl12 and Sl13 accounted for 39.06% and 44.86%,esters accounted for 32.01% and 38.91%.and the acids was 33.96%,the esters was 39.59% in unvaccinated extract.Palmitic acid,stearic acid and 2,4-2 tertiary butyl phenol could be detected in mycorrhizal seedlings rhizosphere,no matter through ethanol or methanol extraction,while only palmitic acid was detected in non-mycorrhizal seedlings.2.The allelopathy of root exudates of mycorrhizal/non-mycorrhizal seedings(1)Under the treatment of high concentration level(1 mg?ml-1),The root exudates of mycorrhizal seedlings and non-mycorrhizal seedlings have negative effect on seed germination rate,germination index,hypocotyl length,radicle length.Under the treatment of low concentration levels(0.25 mg?ml-1),the three kinds of Pinus massoniana seedlings root exudates have positive effect on seed germination and seedling growth.Three kinds of seedlings root exudates have significant difference affect on seed germination of Pinus massoniana(p < 0.05).(2)The root exudates of mycorrhizal/non-mycorrhizal seedlings could promote the growth of seedling height,ground diameter,the accumulation of biomass of one year seedlings of pinus massoniana.Compared with the treatment of control,the inoculated and uninoculated seedlings root exudates promoted the growth of seedlings performance for Sl13>Sl12>CK.Under the treatment of high concentration level(0.25 mg?ml-1),The three kinds of seedlings root exudates could reduce the content of MDA,increase the activity of SOD,POD,decrease the soil acid phosphatase(S-ACP)activity,improve the soil polyphenol oxidase(S-PPO),urease(S-UE)activity and the nutrient content of soil.3.The allelopathy of organic acid allelochemicals(1)Under the treatment of high,medium and low three concentration levels,phthalic acid have negative effect on seed germination rate,germination index,vigor index,hypocotyl length,radicle length,fresh weight and dry weight.Under the treatment of high concentration level(1 mg?ml-1),palmitic acid restrained the seed germination rate,germination index,vigor index,improved the growth of hypocotyl length,radicle length of pinus massoniana seedlings.octadecanoic acid improved the seed germination rate,germination index,vigor index,radicle length,restrained the growth of hypocotyl length.Under the treatment of low concentration levels(0.25 mg?ml-1),palmitic acid and octadecanoic acid performance the allelopathic effect of promoting.Compared with the treatment of control,The three kinds of organic acid allelochemicals refrained the dry matter accumulation of pinus massoniana seedlings.(2)Compared with the treatment of control,under the treatment of high concentration level(1 mg?ml-1),the three kinds of organic acids allelochemicals refrained the growth of one year seedling of pinus massoniana seedling height,ground diameter,total fresh weight and total dry weight,and the inhibiting effect performanced for phthalic acid> octadecanoic acid> palmitic acid.The three kinds of organic acids allelochemicals could increase the content of MDA,reduce the activity of SOD,POD.except the palmitic acid,octadecanoic acid and phthalic acid all reduce the activity of soil,such as acid phosphatase(S-ACP),polyphenol oxidase(S-PPO),urease(S-UE).Under the treatment of low concentration level(0.25 mg?ml-1),The three kinds of organic acids allelochemicals promoted the growth of one year seedling of pinus massoniana,and the acceleration performanced for octadecanoic acid >phthalic acid > palmitic acid.The three kinds of organic acids allelochemicals could increase the content of MDA,increase the activity of SOD,POD,improved the activity of soil of urease.In conclusion,ECM fungi could reconstructure the rhizosphere through altering the profiles of rhizospheric soil extracts,which eventually effect plant growth.