Effect Of Soil Factors On The Symbiotic Relationship Between Bletilla Striata And Mycorrhiza Fungi

In this paper,the combination of optical microscopy,molecular biology and stable isotope techniques was used to study the effects of soil environments(soil moisture content,p H and carbon and nitrogen application)on the diversity,mycorrhizal structure and morphological characteristics of mycorrhizal fungi and carbon and nitrogen stable isotope characteristics and photosynthetic characteristics.The aim is to reveal the influence of soil environmental factors on the symbiotic relationship between B.striata and mycorrhizal fungi,to clarify the response of the symbiotic relationship between the two to the change of soil factors and the tolerance range of soil factors.The main findings are as follows:(1)Under different soil moisture conditions,a total of 305 OTUs,4 phyla and 99 genera were identified in the white and mycorrhizal fungi.The total species number and alpha diversity index of mycorrhizal fungi increased with decreasing soil water content(the total number of fungi with a soil water content of 45% was 18 OTUs less than the soil water content of 15%);There was a certain difference in abundance.With the decrease of soil water content,the dominant mycorrhizal fungi gradually changed into Agaricomycetes,Serendipita,and Hypocreales fungi of the order Agaricomycetes;at the phylum level,the abundance of Ascomycota decreased significantly when the amount of water decreased,while the abundance of Basidiomycota fungus did not fluctuate much;slice observation showed that mycorrhizal fungi entered the cortical tissue through pathway cells under different water content conditions,and then expanded and concentrated in some areas in the cortical cells,but the number of peloton and the infection rate decreased with the decrease of soil water content;in addition,the carbon and nitrogen isotope abundance gradually increased with the decrease of soil water content,but the net photosynthetic rate decreased obviously(When the soil moisture content was 45%,the net photosynthetic rate was 6.65 ± 0.24?mol/(m2s),and the soil photosynthetic rate at 15% was 0.49 ± 0.43?mol/(m2s)).The soil moisture content of 45% was the best level of white and mycorrhizal symbiosis.(2)Under different soil p H levels,a total of 414 OTUs were identified,and there were 4 phyla and 125 genera.Under acidic soil conditions(4< p H <7),the total number of mycorrhizal fungi and the alpha diversity index decreased as the soil water content decreased(the total number of mycorrhizal fungi was 95 OTUs at p H 4.0);Under alkaline soils conditions(7< p H <10),the total number of mycorrhizal fungi species and the alpha diversity index first increased and then decreased with the increase of soil p H,and the total number of mycorrhizal fungi was the highest(178 OTUs)at p H 8.5.Fusarium and Wallemia prefered acid soils,and Serendipita and Aspergillus prefered alkaline environments;the mycorrhizal fungal infection mode was not affected by soil p H,and the pathway cells in the outer cortex invaded the cortical tissue.The infection rate of mycorrhizal fungi and the number of peloton varied with the soil p H,and the infection rate of mycorrhizal fungi and the number of peloton were the highest when the p H was 4.Under different soil p H conditions,there was no significant difference in carbon and nitrogen stable isotope abundance and net photosynthetic rate,but carbon and nitrogen stable isotope abundance and net photosynthetic rate showed a strong negative correlation.The net photosynthetic rate was the highest when the soil p H was 4(7.51 ± 0.72?mol/(m2s)).A soil p H of 4 was the best condition for B.striata plant growth.(3)Mycorrhizal fungi treated with different soil carbon and nitrogen contents identified 386 OTUs,6 phyla and 146 genera.The species,abundance and dominant bacteria of mycorrhizal fungi were quite different under different soil carbon and nitrogen application.When the soil nitrogen content was consistent,the total mycorrhizal fungi and diversity index increased with the increase of soil organic carbon content.When the soil carbon application rate was 0g C/kg or 1g C/kg(sucrose),the species number and diversity index of mycorrhizal fungi increased with the increase of nitrogen application rate;when the soil carbon application rate was 0.5g C/kg,the mycorrhizal fungi and diversity index decreased with the increase of nitrogen application.Sectional observation showed that the entry of cells through the pathway cell was the main way of infection of cortical tissue by mycorrhizal fungi.The rate of fungal infection,the number of peloton and the form of hyphae were different under different carbon and nitrogen application conditions.The combination of 0.5g C/kg carbon application rate and 0.1g N/kg nitrogen application rate(urea)had the highest net photosynthetic rate(5.92 ± 1.19?mol/(m2s)).The medium-carbon and high-nitrogen combination had good carbon and nitrogen levels.