Effects Of Elevated Rhizosphere CO₂ On Growth Of Oriental Melon And Rhizosphere Microorganisms

The rhizosphere is a complex area where soil,plants and microorganisms work together.When the soil is flooded,compacted and poorly ventilated,the concentration of CO₂in the rhizosphere will increase significantly,which will affect the growth of plants.Oriental melon is a plant that is sensitive to rhizosphere gas,and its growth and development are affected by the rhizosphere gas environment.CO₂is one of the important rhizosphere gases,and it is also an inorganic carbon source for soil microorganisms.At present,under the high concentration of rhizosphere CO₂The changes of rhizosphere microorganisms have not been reported yet.Therefore,it is of great significance to explore the effect of elevated rhizosphere CO₂concentration on the melon rhizosphere microorganisms,which is of great significance to improve the oriental melon rhizosphere environment and the rational use of rhizosphere CO₂.In this experiment,substrate cultivation was used,and the melon rhizosphere was treated with different concentrations of CO₂to make it reach a high concentration of CO₂.Three representative CO₂concentrations selected in the previous preliminary test:T1（0.6%）,T2（0.9%）and T3（1.2%）were used as the treatment group,and the normal rhizosphere CO₂concentration was used as the control group CK（0.3%）.%),experimenting.Through the determination of the growth indicators of melon seedlings,the physical and chemical properties of the rhizosphere matrix,and the use of high-throughput sequencing technology,the effects of high concentration of CO₂in the rhizosphere on the growth of melon seedlings and rhizosphere microorganisms were explored.The main test results are as follows:1.After 10 days of rhizosphere high-concentration CO₂treatment,the plant height,stem thickness,dry and fresh weight,root vigor,photosynthetic pigment and photosynthetic parameters of muskmelon seedlings under T2 and T3 treatments were significantly reduced compared with CK.The decrease of potassium accumulation indicates that the growth and photosynthesis of muskmelon seedlings are inhibited,but there is no significant effect under T1 treatment.After 20 days,T1 treatment also began to inhibit the growth and photosynthesis of oriental melon seedlings.2.After 10 days of rhizosphere high-concentration CO₂treatment,compared with CK,the p H of rhizosphere substrate decreased significantly with the increase of CO₂concentration;the content of alkali-hydrolyzable nitrogen decreased significantly,but there was no significant difference between the treatments.After 20 days,the content of available potassium and organic matter began to decrease,the EC value increased,and there was no significant change between treatments.The content of available phosphorus was not affected under high concentration CO₂treatment.3.Rhizosphere high-concentration CO₂treatment for 30 days,compared with CK,with the increase of CO₂concentration,the number of bacteria first decreased and then increased,which was the least under T1 treatment;the number of fungi first increased and then decreased,and was the most under T3 treatment;actinomycetes The number is gradually decreasing.Analysis of bacterial community structure through high-throughput sequencing technology found that high concentrations of CO₂significantly reduced the diversity and abundance of bacteria,and some primitive flora mutated or even died under high concentrations of CO₂.Under T1,T2 and T3 treatments,the composition of the bacterial community also separated from CK,indicating that the genetic evolution of the bacterial community has changed,but the main bacterial species did not change.4.At the phylum level,Chloroflexi,Actinobacteria,Firmicutes,Bacteroidota,Actinobacteriota,Firmicutes,Bacteroidota and Acidobacteriota are the main phyla.With the increase of CO₂concentration,the abundance of Chloroflexi,Proteobacteria,Firmicutes,and Bacteroidota did not change significantly,and the abundance of Acidobacteriota and Proteobacteria The relative abundance of Proteobacteria showed an upward trend.At the genus level,SBR1031 genera,Actimomarinales genera,A4b genera,JG30-KF-CM45 genera,Galbitalea genera,and AKYG1722 genera were mainly detected.Among them,the relative abundance of SBR1031,A4b,and Galbitalea gradually increased with the increase of CO₂concentration,and there was no obvious change in Actimomarinales,JG30-KF-CM45 and AKYG1722.5.Correlation analysis showed that the abundance of Actinobacteria（Actinobacteriota）was significantly positively correlated with p H;the abundance of Proteobacteria（Actinobacteriota）was significantly negatively correlated with available potassium;the abundance of Actinobacteria（Actinobacteriota）was significantly correlated with available potassium,EC value,p H value and organic matter content are significantly negatively correlated.A4b genus is significantly negatively correlated with available potassium;Galbitalea genus is significantly positively correlated with available potassium,EC value and p H.The AKYG1722 genus is significantly negatively correlated with available potassium,EC value,p H and organic matter.