| Biochar is a stable carbon-rich product synthesized through pyrolysis of plant-and animal-based biomass.The application of biochar in agricultural production can promote the growth and development of crops.However,there are few studies on the effects of water-soluble substances in biochar on crop growth and soil microorganisms.In this thesis,the effects of biochar water extract on barley germination,growth and rhizosphere microflora were studied and the barley rhizosphere growth-promoting bacteria were isolated,identified and characterized.Besides,the metabolic changes of biochar water extract on barley grain were analyzed and the physiological mechanism of biochar water extract promoting crop growth was explored.The main findings are as follows:1.The effects of different concentrations of water extracts of rice husk carbon,straw carbon and corncob carbon on barley germination performance,endogenous hormones,hydrolase activity and endosperm hydrolysis were determined.The results showed that when the concentration of corncob carbon aqueous extract was 10%,it had the most significant promoting effect on barley germination performance,endogenous hormone activity,hydrolase activity and endosperm hydrolysate,which was 1.9% ～ 89.3% higher than that of the control group;The content of abscisic acid and β-glucan was 50% and 27.8% lower than that of the control group respectively.Therefore,the aqueous extract of corncob charcoal can significantly promote the germination of barley.2.In order to clarify the effect of biochar water extract on the growth and development of barley seedlings,corncob carbon water extract,the concentrations of which were 0.1%,1%,10% and 100% respectively,was applied as the barley grew.The results showed that when the concentration of corncob carbon aqueous extract was 10%,it had the most significant effect on the growth index,chlorophyll content,root absorption capacity,protective enzyme and stress resistant enzyme activities of barley seedlings,which were 10% ～ 67% higher than those of the control group.When the concentration was 1%,the soluble protein content and catalase(CAT)activity were 10% and 35% higher than those of the control group respectively.Therefore,when the concentration of corncob carbon aqueous extract was 1% and 10%,it had the most significant effect on the growth of barley.3.In order to reveal the effect of biochar water extract on the structure of barley rhizosphere flora,the total DNA of barley rhizosphere soil was sequenced.When the concentration of corncob carbon water extract was 1% and 10%,the difference of flora abundance in barley rhizosphere soil was analyzed and the function of barley rhizosphere bacteria was predicted.The results showed that the aqueous extract of corncob charcoal could significantly reduce the richness and diversity of bacterial community in barley rhizosphere.LEf Se analysis showed that when the concentration of corncob carbon aqueous extract was 1%,the abundance of 21 genera such as Acinetobacter increased significantly;When the concentration was 10%,the abundance of 18 genera such as pan bacteria increased.The prediction of the treatment of corncob carbon aqueous extract involves the functions of bacterial nitrogen fixation,glycolysis,phosphorus dissolution and amino acid degradation in barley rhizosphere.Therefore,when the concentration of corncob carbon aqueous extract was 1% and 10%,it had the most significant effect on the enrichment of barley rhizosphere growth promoting bacteria.4.The growth promoting bacteria in barley rhizosphere treated with biochar aqueous extract were isolated,identified and characterized.The 7 strains were identified as Bacillus amyloliquefaciens,Bacillus pumilus,Bacillus megaterium,Acinetobacter Qiong,Sphingomonas,Bacillus subtilis and paenibacillus.Among them,Acinetobacter Qiong has the strongest ability of dissolving inorganic phosphorus and organic phosphorus,nitrogenase activity and secreting IAA.And Bacillus megaterium has the strongest antibacterial ability against Fusarium.The germination rate of barley was the highest after application of Bacillus amyloliquefaciens,which was 2.7% higher than that of the control group.Paenibacillus improved the growth index of barley most significantly,17.7% ～ 28% higher than that of the control group.Bacillus amyloliquefaciens and Paenibacillus promoted the change of aboveground biomass of barley most significantly,which was 13.1% higher than that of the control group.After applying the aqueous extract of corncob charcoal,the bacterial concentration and nitrogenase activity of Paenibacillus were 37.5% and 23.1% higher than those of the control group,respectively.The dissolving ability of Bacillus amyloliquefaciens to organic phosphorus and potassium and biofilm forming ability were 18.8% ～ 52.2% higher than those in the control group;The solubility of inorganic phosphorus by Acinetobacter Qiong was 24.1% higher than that in the control group.Therefore,among the 7 strains isolated,screened and identified from barley rhizosphere,Bacillus amyloliquefaciens and Paenibacillus had the most significant effect on the growth of barley.5.In order to clarify the effect of barley rhizosphere growth promoting bacteria on barley yield and grain metabolites,1% concentration of corncob carbon water extract,amylolytic bacillus and paenibacillus were added respectively.The yield and other indexes were measured after barley ripening.The metabolites and differential multiples of barley grains were analyzed,the differential metabolites of barley grains were screened and the metabolic pathway was analyzed.Results under the combined action of corncob carbon water extract and barley rhizosphere growth promoting bacteria,barley yield,barley quality and germination performance were significantly improved,which were 2.7% ～ 25.9% higher than those in the control group,and the increase of total metabolite content in barley grain was the largest.PLS-DA analysis combined with analysis of variance screened 22 different metabolites.Metabolic pathway analysis mapped 12 metabolic pathways,of which 4metabolic pathways significantly related to different metabolites,were related to amino acid metabolism and biosynthesis,of which the most significant metabolic pathway was aminoacyl t RNA biosynthesis.The results showed that the aqueous extract of corncob carbon could increase the abundance of growth promoting bacteria in barley rhizosphere,and then improve the yield and quality of barley. |
