Regulation Of Banana Arbuscular Mycorrhizal Colonization And Phosphorus Supply On Nutrient Uptake

Using two banana cultivars,Baodao and Baxi,this study combined two experiments:firstly,a pot experiment was carried out in greenhouse to study the effects of different phosphorus(P)supply levels on plant growth,nutrient uptake,arbuscular mycorrhizal(AM)colonization and P acquisition by mycorrhizal hyphae;secondly,a field experiment was conducted to compare the dynamics of AM colonization for the two banana cultivars.The pot experiment set three P supply levels(0,50,500 mg P/kg)on a low-P acid soil.Based on this,heterogeneous P supply in plastic chambers adding with 50 mg P/kg was set,with +H soil chamber enclosed with 30 ?m mesh fabric to allow passage of mycorrhizal hyphae alone and-H soil chamber enclosed with 0.45 ?m microfiltration membrane to prevent passage of both root and mycorrhizal hyphae.After about five month,plants were sampled to measure growth parameters,nutrient uptake,AM colonization level,mycorrhizal hyphae density and soil available P change.The field experiment was conducted with sufficient nutrient and water supply,and roots were sampled monthly to measure AM colonization level.+H and-H soil chambers were also installed at distance of 30 cm and 60 cm from plant,and soil available P level in chambers were measured at fast growth,flowering and maturity stage.The main results were as follows:1.In pot experiment,increasing P supply increased plant growth for both banana cultivars,with highest plant height and dry weight obtained under 500 mg P/kg.With increasing P supply,P and potassium concentrations and total uptake increased,while copper concentration and uptake decreased.Because of increased plant biomass,the total uptake of nitrogen,calcium,magnesium and zinc increased with increase of P supply.As P supply level rose up,Baodao showed decreased uptake of iron but increased uptake of manganese,whereas iron uptake of Baxi gradually increased and manganese uptake showed an up-and-down trend.2.In pot experiment,AM colonization was significantly influenced by P supply level.AM colonization level was highest under 50 mg P/kg for Baodao,but under 0 mg P/kg for Baxi,respectively.The high P level(500 mg P/kg)severely inhibited AM colonization for both cultivars.3.In pot experiment,with increasing P supply,mycorrhizal hyphae density in soil decreased.At the same P supply level,mycorrhizal hyphae density showed an order of bulk soil>+H chamber soil>-H chamber soil.Soil available P level was lower in+H chamber that in-H chamber.With increasing bulk soil available P level,P acquisition from +H chambers by mycorrhizal hyphae reduced.4.Under field condition,both banana cultivars had very low level of AM colonization,with an increase occurring in the middle growth stage.With sufficient supply of nutrients and water,P acquisition by mycorrhizal hyphae was severely inhibited.From these results,it can be concluded that on low-P soils increasing P supply increased plant growth and uptake of most nutrients for the two bananas.AM colonization and soil mycorrhizal hyphae density were influenced by P supply level,namely low or middle P supply level increased AM colonization and hyphae density,but sufficient nutrients and water supply restricted.AM hyphae could explore localized P supply according to bulk soil P availability,with higher P acquisition by hyphae occurring when bulk soil available P level was lower than localized P supply.