Allelopathic Effects Of Ficus Carica Linn.extract On Seed Germination And Seedling Growth Of Isatis Indigotica Fort

Fig（Ficus carica Linn.）is one of the widely distributed fruit trees in China.It is a kind of perennial deciduous shrub with rapid growth and broad branches and leaves.In recent years,it has been paid more attention as a medicinal and food homologous plant.Fig allelochemicals exist in various organs and can produce different degrees of allelochemicals on the surrounding plants.In this study,the allelopathic effects of fig extract on Isatis indigotica Fort.were studied by filter paper culture,tissue culture and greenhouse pot experiment,and the potential allelochemicals were identified.By analyzing the changes of physiological indexes of Isatis indigotica F.in tissue culture and pot seedling growth,the allelopathic mechanism of potential allelochemicals of fig on seed germination and seedling growth of Isatis indigotica F.was clarified,which could provide theoretical reference for making full use of fig resources and improving the yield of Isatis indigotica F..The results are as follows:（1）The aqueous extracts of fig roots,stems and leaves at different concentrations（12.50,25.00 and 50.00 g/L）were obtained by distilled water extraction,and the allelopathic was determined using Isatis indigotica F.seeds and seedlings as the receptor.The allelopathy of figs on the germination of Isatis indigotica F.seeds was in the following order:stem>leaf>root.The promotion effect of different parts of figs on the growth of Isatis indigotica F.seedlings was ranked from largest to smallest:leaf>stem>root.（2）The aqueous extracts of fig leaves were extracted with petroleum ether,ethyl acetate,and n-butanol,and the extracts of each part were applied to Isatis indigotica F.seedlings in tissue culture for the determination of allelopathic activity,and it was found that the allelopathic promotion effect of ethyl acetate part was the most obvious,and these indexes were the highest in all treatment groups in terms of seedling emergence rate,above-ground fresh weight,total leaf area,seedling height and main root length.The order of allelopathic promotion effect of different polar extracts treating Isatis indigotica F.seedlings in tissue culture was:ethyl acetate phase>petroleum ether phase>n-butanol phase.（3）Nine fractions were obtained by column chromatographic separation and TLC detection,and two fractions with high allelopathic activity,Fr.5 and Fr.8 were further separated and purified according to the bioassay results to obtain three allelopathic compounds,which were identified by UV spectroscopy,IR spectroscopy,NMR and high-resolution mass spectrometry,and the three substances were obtained as:psoralen,bergapten and umbelliferone.（4）The initial identification of the three allelochemicals in fig leaves was replaced by exogenous compounds,and the allelopathic activities of Isatis indigotica F.in tissue culture seedlings was measured respectively.The results showed that:the seedling height and main root length of 0.0125 mg/m L bergapten seedlings were the longest,which were increased by 67.79%and 80.60%compared with the control,respectively.For the three indexes of above-ground and underground fresh weight,total leaf area and total leaf number,bergapten treatment groups with three concentrations were significantly higher than the control group,and the variation trend was consistent.Except 0.00625 mg/m L umbelliferone treatment group,the other treatment groups showed significant inhibition.In a word,all three allelopathic substances showed allelopathic effect of"low promotion and high inhibition".（5）The growth indexes of pot seedlings of Isatis indigotica F.treated with allelochemicals showed that the changes in seedling height,root length and above-ground and underground biomass after treatment with three different concentrations of allelochemicals were consistent with the concentration effect of"low promotion and high inhibition",100 ppm,150 ppm bergapten,100 ppm psoralen and 50 ppm umbelliferone promoted the growth of seedlings,while the other concentrations of umbelliferone inhibited the growth of Isatis indigotica F.seedlings.（6）The activities of superoxide dismutase（SOD）,peroxidase（POD）,and catalase（CAT）and the content of malondialdehyde（MDA）in pot seedlings of Isatis indigotica F.treated with allelochemicals were determined.The results showed that psoralen had a trend of first increasing and then decreasing on the activities of three protective enzymes with the increase of concentration.The SOD and CAT activities of bergapten on pot seedlings of Isatis indigotica F.showed a"up-down"trend,and the POD activities showed a"down-up-down"trend.Under umbelliferone treatment,the activities of three protective enzymes showed a"down-up-down"trend,and the content of MDA was positively proportional to the concentration,among which the MDA content of umbelliferone was the highest.（7）The effects of net photosynthetic rate（Pn）,transpiration rate（Tr）,stomatal conductivity（Gs）and intercellular CO₂ concentration（Ci）on pot seedlings of Isatis indigotica F.decreased with the increase of bergamolide and umbelliferone concentrations,while Pn,Gs and Ci in psoralen treatment group presented a"low-high-low"trend with the increase of concentrations.Under 100 ppm bergapten treatment,the chlorophyll content and photosynthesis of Isatis indigotica F.were the highest.The soluble protein content increased firstly and then decreased with the increase of allelochemicals concentration,the soluble sugar content was proportional to the concentration,and the root activity decreased with the increase of allelochemicals concentration.The allelopathic promotion effects of the three potential allelochemicals in fig leaves were in order of magnitude:bergapten>psoralen>umbelliferone.