Study On The Effects Of Coumarin And Vanillic Acid On The Seed Germination And Seedling Growth Of The Invasive Plant Bidens Pilosa

Biological invasion is the main cause of global biodiversity loss,second only to habitat destruction.As the group with the highest proportion of invasive species,invasive plants are large in number and cause great harm.Among them,invasive plants of the Compositae are the first.Bidens pilosa is a typical malignant weed of the Compositae.It has strong habitat occupation ability,high seed germination rate,and strong phenotypic plasticity.It has been flooded.Commonly used chemical reagents gradually lose their effectiveness on B.pilosa,and the application of chemical herbicides has caused great harm to the ecological environment.How to develop new ecologically safe herbicides is an urgent problem to be solved,and allelochemicals are to solve this problem.There are new ideas and hopes,but the research on B.pilosa is rarely reported.Coumarin and vanillic acid are allelochemicals widely present in plants and are harmless to the environment.Therefore,this study took B.pilosa as the research object,used petri dish experiments and pot experiments,set up different treatment liquid gradients,and exploring the possibility of using coumarin and vanillic acid on seed germination,seedling growth and physiology of B.pilosa seeds under separate and mixed treatments to explore the possibility of these two allelochemicals as green herbicides,with a view to preventing and controlling invasive plants provide theoretical basis.The results of the study are as follows:（1）Vanillic acid treatment and mixed treatment showed low-concentration promotion and high-concentration inhibitory effects on the germination rate and germination index of seeds,while coumarin treatment showed inhibitory effects.The higher the concentration,the greater the inhibitory intensity.Different treatments all inhibited the length of the radicle and hypocotyl of B.pilosa,and the inhibitory effect continued to increase as the treatment concentration increased.（2）Under different treatment methods,with the increase of time,the fresh weight,dry weight biomass,root and leaf morphological indexes,plant height,and base diameter of seedlings in each group continued to increase,but at any time period,all treatment methods are low-concentration promotion and high-concentration inhibition.Different treatments inhibited the root vitality of B.pilosa.With the increase of the treatment concentration,the inhibitory intensity increased,but the change trend of the root vitality of each concentration under different treatments was different;100 mg/L coumarin treatment group,the root vitality showed a trend of first rising and then decreasing with time,and the other groups showed a continuous downward trend;the root vitality of each group under vanillic acid treatment increased with time and showed a trend of first decreasing and then rising;under mixed treatment the root vigor of each group showed a trend of first decreasing,then increasing and then decreasing with time.（3）Different treatments have significant effects on the physiological and biochemical indexes of B.pilosa:1)Activity of antioxidant enzymes is different,but each treatment is promoted by low concentration and inhibited by high concentration;SOD activity increases with the treatment time.It increased first and then decreased.The coumarin treatment group had the maximum value on the 14 th day,the vanillic acid treatment group had the maximum value on the 7 th day,the mixed treatment high concentration group had the maximum value on the 14 th day,and the other groups had the maximum value on the 7 th day.There is a maximum value;the POD activity first increased and then decreased and then increased with the increase of the treatment time,and each group had a minimum value on the 14 th day;the CAT activity first decreased,then increased and then decreased with the increase of the treatment time,each group both have a maximum value on the 14 th day.2)The proline content of the coumarin-treated high-concentration group increased with the increase of the treatment time,while the other groups first increased,then decreased,and then increased;the vanillic acid treatment group and the mixed treatment group increased firstly with the increase of treatment time and concentration The trend of high and then decreasing,there is a minimum at 14 day.3)With the increase of treatment time and concentration,the MDA content,soluble sugar,soluble protein content,and ABA content increased significantly,while the GA₃ content decreased significantly.4)Different treatment methods all inhibit the photosynthesis of B.pilosa.As the treatment concentration increases,the inhibitory intensity increases;as the treatment time increases,the chlorophyll content,stoma conductance,intercellular CO₂ content,and chlorophyll a/b of each group increase.The value of increased first and then decreased,while the net photosynthetic rate and transpiration rate continued to decrease.（4）Principal component analysis results show that coumarin and vanillic acid inhibit the germination process of seeds by affecting the germination index and hypocotyl length of B.pilosa;by affecting plant biomass,hormone content,and growth status of vegetative organs,Photosynthesis and antioxidant enzyme activity and osmotic adjustment substance content interfere with the growth of seedlings,which mainly affect the growth of roots and leaves.Correlation analysis results show that there is a very significant positive correlation between the various indicators of seed germination,and the various growth indicators of seedlings are also very significant positive correlations.Root growth changes have a greater impact on root vitality,while other indicators are related to root vitality is not strong.Different physiological and biochemical indexes have different effects on the same growth index or different growth indexes have different influences on the same physiological index.Each index comprehensively affects seeds and seedlings.（5）The comprehensive allelopathic effect shows that the different concentration treatments of different methods have an inhibitory effect on the germination process of seeds;the low concentration treatments of different methods have a certain promotion effect on the growth of seedlings,and the high concentration has an inhibitory effect.,With the increase of treatment concentration,the inhibitory effect increases;seeds are more sensitive to coumarin and vanillic acid treatment than seedlings;allelopathic strength:coumarin treatment>mixed treatment>vanillic acid treatment;mixed treatment of coumarin and vanillic acid has an antagonistic effect;coumarin has the potential to be used as an environmentally friendly agent to control B.pilosa.In view of the actual situation,combined with the research results,the following prevention and control suggestions are put forward:（1）Screen the dominant native plants rich in coumarin and plant them in the B.pilosa invaded fragile habitats,and use GPS and remote sensing technology to track,monitor and control as much as possible Effect,avoid secondary invasion.（2）In areas where B.pilosa is distributed,spraying coumarin on the roots of seedlings can have a control effect,and it is necessary to strengthen the research on the synthesis of more green herbicides using coumarin as the precursor and gradually apply them in practice.（3）Strengthen the investigation and research of invasive plants,screen native plants that have similar niches to invasive plants in the community,and combine alternative control methods to gradually achieve ecological restoration effects.