| Rhus typhina L.,a deciduous shrub or subtree belonging to Anacardiaceae,Rhus.,has high economic value,medicinal value and ornamental value and it is widely used in landscaping.Rhus typhina updates propagation speed in the botanical garden afforestation,which can reduce the number of species diversity,the change of soil physical and chemical properties,so researchers focus more on its invasion mechanism,especially on its allelopathy.However,few research has been done on whether the Rhus typhina by allelopathy affects other plant rhizosphere microbes and has an influence on the growth.In this experience,potted plant control experiment and Biolog-ECO micro-plate method were used to study the effects of aqueous extract from Rhus typhina roots on the growth of four compositive plants(Cosmos bipinnata,Zinnia elegans Tagetes erecta and Rudbeckia hirta)seedlings and the carbon source utilization of underground soil microorganisms.The relationship between the aqueous extract of Rhus typhina root and the growth of plants,the physicochemical properties of soil,and the use of carbon source by soil microbial community was studied,and the allelopathic mechanism of Rhus typhina on garden plants was researched.The main research results are as follows:1.4 kinds of concentration treatment of Rhus typhina root aqueous extracts all inhibited the growth of Tagetes erecta plant height,stem diameter and the increase of aboveground biomass;The seedling growth of the other two plants presented a trend of "low promoting but high inhibiting" on the whole.The root aqueous extract of high concentration(0.4 g·ml-1)inhibited the seedling growth,and the seedling growth was suitable when the concentration was 0.2 g·ml-1-0.3 g·ml-1.2.The aqueous extract from the Rhus typhina root had no effect on the soil water content of Cosmos bipinnata,Tagetes erecta and Rudbeckia hirta,but all of them reduced the organic carbon content and total nitrogen content of Tagetes erecta roots soil,and increased the soil p H.At 0.2g ·ml-1-0.3g ·ml-1,the soil conductivity,p H,organic carbon and total nitrogen content of Cosmos bipinnata,Zinnia elegans and Rudbeckia hirta were increased;The contents of organic carbon and total nitrogen in plant soil were reduced at 0.4 g·ml-1.3.The time when AWCD(Average Well Color Development)value reached stable stage varied with plant species.(Cosmosbipinnata 180 h,Zinnia elegans 204 h,Tagetes erecta 192 h,and Rudbeckia hirta 156 h);The AWCD values of the soil microorganisms of the four plants were significantly different because of the different concentrations of extracts.The AWCD values of Tagetes erecta were the highest when the concentration was 0 g· ml-1,while the AWCD values of Zinnia elegans,Cosmos bipinnata,Rudbeckia hirta were the highest when 0.1 g·m L-1,0.2 g·m L-1 and 0.3 g· ml-1,respectively.All the 4 plants reached the lowest level at 0.4 g· ml-1.4.The utilization rate of soil microorganisms to the six carbon sources varies with plant species.Compared with the control group,other concentrations of Rhus typhina root aqueous extract all promoted the utilization of amines by rhizosphere soil microorganisms of Cosmos bipinnata,carbohydrate by soil microorganisms of Zinnia elegans,and Rudbeckia hirta,and phenolic acids by soil microorganisms of Tagetes erecta.Moreover,the utilization of amino acids,amino acids and amines by the soil microorganisms of Cosmos bipinnata,amino acids,phenolic acids and amines by the soil microorganisms of Zinnia elegans,carbohydrates,carboxylic acids and polymers by the soil microorganisms of Tagetes erecta,and polymers,amino acids and amines by the soil microorganisms of Rudbeckia hirta decreased.5.The diversity index of soil microbial carbon source utilization reflects the richness of species in soil microbial community and the concentration of soil microbial dominant species.Through the analysis of soil microbial diversity index of plant root soil,it was found that the Shannon-wiener diversity index,Pielou diversity evenness index and Gini diversity index of Tagetes erecta soil microbial carbon source were higher than those of the other three plants,but lower than the control.The Shannon-wiener diversity index and Gini diversity index of Zinnia elegans were decreased.The pielou diversity index of Cosmos bipinnata soil microbial carbon source was higher than that of control.When the concentration of root aqueous extract from the Rhus typhina was 0.2 g·ml-1,the diversity of Rudbeckia hirta soil microbial carbon sources was the highest among the three species.When it was 0.3 g·ml-1,the diversity index of Shannon-wiener used by the microbial carbon source of Cosmos bipinnata soil was the highest,while the Pielou evenness index of Zinnia elegans was the highest.6.The correlation between AWCD value,diversity index,growth index and environmental index of soil microbial carbon source varies with different plant species.The AWCD value of soil microorganisms of Cosmos bipinnata,Tagetes erecta and Rudbeckia hirta showed a significant positive correlation with soil organic carbon and total nitrogen content,and an extremely significant negative correlation with Zinnia elegans.There was a significant positive correlation between AWCD and aboveground biomass with Cosmos bipinnata,Tagetes erecta and Zinnia elegans.The Pielou evenness index,shannann-wiener diversity index and Gini diversity index of soil microorganisms of Tagetes erecta and Rudbeckia hirta were significantly negatively correlated with soil p H.7.The results of RDA(Redundancy Analysis,RDA)showed that organic carbon and total nitrogen were the main factors affecting soil microbial changes of the four plants.To sum up,the different concentrations of Rhus typhina roots aqueous extract has a certain allelopathic effect on 4 compositae plants,mainly manifested as “low-promoting and high-inhibiting”,but the aqueous extract from the roots of Rhus typhina has the greatest influence on Tagetes erecta.Under different concentrations,the content of organic carbon and total nitrogen in the Tagetes erecta soil decreased.Meanwhile,the utilization of carbohydrates,carboxylic acid and polypolymer by soil microorganisms,and the number and diversity of soil microbial population were reduced,thus the growth of Tagetes erecta was affected.This study provides a theoretical basis for the research on the influence of allelopathy on the growth of other plants,and provides theoretical guidance for the plant configuration of torchbearers,which is of great significance in urban ecological construction and landscaping. |
PDF Full Text Request