| Phosphorus(P)is one of the major factors limiting crop growth worldwide,because most soil P exists in pools of low availability.Molybdenum(Mo)is a trace element found in soil and is required for microorganism and plants growth.Synergistic effects exist between Mo and P in plant.However,molybdenum-induced effects on the dynamics of P in the rhizosphere of different crops have still not been investigated.Here,the long term field study was carried out to investigate the effects of Mo supply(-Mo and +Mo)on microbial population structure,variation of metabolites,phosphorous transformation characteristics in rhizosphere and non-rhizosphere soil in leguminous and nonleguminous crops system.(1)16S r RNA sequencing analysis revealed that Mo application affected varies at genus and class level.As compared to-Mo treatment,higher percentage of Proteobacteria and Acidobacteria were observed in +Mo treatment both in soybean and maize rhizosphere soil.These both phylum(Proteobacteria and Acidobacteria)accounted together for 39.43%,57.74% –Mo and +Mo respectively in soybean rhizosphere soil,while 44.51% and 46.64% in maize rhizosphere soil.At class level,there was significant differences in the Accidobacteria,Ktedonobacteria,iii-8,Actinobacteria,Thermomicrobia,Gemmatimonates,Deinococci,DA052 and ?,?-proteobacteria between-Mo and +Mo treatment in soybean rhizosphere soil.In miaze there were significant differences in Acidobacteria,Actinobacteria,Cytophagia,?,?,and ?-proteobacteria,TK-10 and 4Cod-2 between the-Mo and +Mo.Lef Se analysis indicated that 105 and 40 biomarkers were respectively associated the maize and soybean crop between-Mo and +Mo treatment across all taxonomic levels.It is clear from these results that molybdenum has a significant role in shaping the microbial community structure and diversity,while the differential response also existed between the soybean and maize rhizosphere soil.(2)The metabolites profiling of maize and soybean rhizosphere soil extraction were analyzed in molybdenum applied and without molybdenum application treatment.There were respectively 8 and 10 differential metabolites between-Mo and +Mo treatment in maize and soybean rhizosphere soil,which were mainly microbial metabolites.In-Mo treatment,there were 53 significantly differential metabolites between maize and soybean.In +Mo treatment,there were 70 significantly differential metabolites between maize and soybean rhizospere soil,which included the carbohydrate,organic acid,amino acid,lipid and other secondary metabolite.These results indicated that the crop type have greater effects on metabolites in rhizosphere soil relative to Mo application.(3)Phosphorous transformation characteristics were investigated in leguminous and non-leguminous crop system.The results showed that Mo application decreased the p H of the rhizosphere soil both in leguminous and non-leguminous crop system,while Mo deficiency have higher p H level for non-rhizosphere soil both in leguminous and nonleguminous crop system.On the contrary,Mo application increased the organic matter of the rhizosphere soil both in leguminous and non-leguminous crop system,while Mo deficiency decreased organic matter for non-rhizosphere soil both in leguminous and non-leguminous crop system.Similarly,Mo application increased the microbial phosphorus of the rhizosphere soil both in leguminous and non-leguminous crop system,while Mo deficiency decreased microbial phosphorus for non-rhizosphere soil both in leguminous and non-leguminous crop system.Molybdenum application significantly increased the available P fractions(H2O-Pi and Na HCO3-Pi)in rhizosphere and nonrhizosphere soil of both leguminous and non-leguminous crops system.Moreover,as compared with-Mo,Mo application significantly increased soil acid phosphatase,alkaline phosphatase and phytase in both leguminous and non-leguminous crops.Mo application significantly up-regulated the expressions of pho N/pho C,pho D and BPP genes.Expression of these genes was higher in the rhizospeher soil as compared to nonrhizosphere soil both in leguminous and no-leguminous crops.In short,our study findings imply that Mo supply increased P bioavailability through enhancing P enzymatic activity and P related genes expression.(4)Phosphorus uptake efficiency can be enhanced by Mo application in different crops and more specifically Mo can help to maintain the stability of chloroplast structure.There were significant differences in biomass,grain yield and nutrient acquisition between the Mo application and the control treatments.Mo supply ameliorated chloroplasts deformation in the leaves compared with-Mo treatment.+Mo treatment leaves had greater stomatal length and width.The results imply that Mo-induced increases in plant biomass and grain yield through increased P in different parts of the crops and by preserving the chloroplast,stomatal and mesophyll tissue cells configuration,suggesting that Mo has more complementary effects to plant yield and P assimilation. |
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