| To explore the allelopathy of the exotic Thalia dealbat, the study analyzed the chemicalcomponents of aquatic leaf, leafstalk and root extracts of T. dealbat. with the chromatography/massspectrum (GC/MS). Altogether, the study measured the effects from aquatic leaf, leafstalk and rootextracts of T. dealbat on seed germination of3vegetables (Raphanus sativus, chinese cabbage,Cucumis sativus). The study measured the effects from aquatic root extracts of T. dealbat on seedgermination of6species (Nymphoides peltatum, Vallisneria natans, Nasturtium officinale, Irispseudacoru, Phragmites australi, Polygonum hydropiper) and the effects in seedlings of5species(Nymphoides peltatum, Vallisneria natans, Nasturtium officinale, Phragmites australis, Irispseudacorus) using the biossay. The results as follows:1. There were sixty-eight compounds in different organs of the aquatic extracts of T. dealbat.Themain compounds in the aquatic leaf extracts of T. dealbat were lauryl acrylate(35.35%),coumaran(9.78%), etc.. The main compounds in the aquatic leafstalk extracts were coumaran(31.61%), diisobutyl phthalate (21.72%), etc.. The main compounds in the aquatic root extracts wereguaiacol (83.05%), diisobutyl phthalate (4.75%), etc..2. Test results indicate that extracts from different parts of the plant all have inhibition effect on thethree test species, among which extract from leaf tissue showed the most significant effect. Leafextract (50Dw·mL-1) significantly (P<0.05) affects test plants respectively with an inhibition rate of30.49%～40.26for Turnip,2.33%～85.19%for Chinese Cabbage and0%～10.53%for Cucumber.Results also indicate that extracts from all parts of Thalia dealbata could inhibit seedling growth.Negative effects were detected in root length, shoot length, fresh weight and dry weight in theexperiment on the three plants. And this effect of inhibition showed a positive correlation with theconcentration of tissue extracts. High density extracts showed significant (P<0.01) inhibition onseedling growth. Inhibition rate of50Dw·mL-1extract solution on root length was51.21%for Turnip,91.7%for Chinese Cabbage and45.71%for Cucumber, and inhibition rate on shoot length was51.21%,69.66%and45.71%respectively. Also it could be concluded that allelochemicals exist in allpart of Thalia dealbata and the strongest allelopathic effect came from rhizome, followed by root,leafstalk and leaf tissue.3. The results showed that the aquatic rhizome and root extract of T. dealbat had significantallelopathic effects on seed germination of the six aquatic plant species，with the effects varying withthe concentration of the extract. Extracts at a concentration of50Dw·mL-1were found to beinhibitory(P＜0.01) to seed germination for the six aquatic plant species, the shoot length in theseedlings were reduced by29.2%,64.9%,42.3%,87.1%,18.16%and75.6%; the root length in theseedlings were reduced by50.5%,90.1%,72.7%,76.2%,29.9%and74.2%. In addition, the seedgermination index was more sensitive to extract application than the germination percent and otherindexes, with allelopathic sensitivity in the order of P. hydropiper﹥N. officinale﹥V. natans﹥I.pseudacoru﹥N. peltatum﹥Ph. australi.4. Results showed that the aquatic rhizome and root extract of T. dealbata had significantallelopathic effects on seedling growth in N. peltatum, V. natans, N. officinale, Ph. australis and I.pseudacorus, with the effects varying with the type of pasture plants and the concentration of theextract. The seedling growth index in N. peltatum, V. natans, N. officinale, Ph. australis and I.pseudacorus was highly significantly inhibited by treatment with50Dw·mL-1of the aquatic extract;the net photosynthetic rate in the seedlings of V. natans, N. officinale and I. pseudacorus were reduced by69.0%,63.7%and73.5%; the root activity in the seedlings of N. peltatum, V. natans, N. officinale,and I. pseudacorus were reduced by67.3%,65.4%,52.2%and46.7%, respectively, and thechlorophyll content in the five aquatic plants were reduced by59.7%,71.2%,35.2%,50.0%and76.5%, respectively, compared with the control. At5Dw·mL-1, the extract significantly increased theactivities of superoxide dismutase (SOD), peroxidase(POD), and catalase(CAT); whereas at50Dw·mL-1the extract reduced the activities of those enzymes while significantly increased the contentof malondialdehyde(MDA)in the seedling of the aquatic plants.The results of this study firstly proved that there were allelopathy effect in T. dealbata and providedthe basic theory for the mechanism of the formation od mono-dominant community of T. dealbata.And then it will help the selection and design of landscape plants. |
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