AMF对不同水分条件下紫花苜蓿生态化学计量学特征的影响

为研究丛枝菌根真菌(AMF)对不同水分条件下紫花苜蓿(Medicago sativa)营养元素含量及生态化学计量学特征的影响,试验以紫花苜蓿阿尔冈金(M.sativa cv.Algonquin)为材料,通过温室盆栽的方法,在模拟干旱和正常供水两个水分梯度下,单接种丛枝菌根真菌AMF(Glomus constrictum,M)、单接种根瘤菌(Sinorhizobium meliloti,R)、双接种R和M(RM)以及不接种(CK),测定紫花苜蓿叶片和根系中碳(C)、氮(N)、磷(P)、钾(K)的含量并计算其生态化学计量学特征。结果显示,干旱胁迫降低了紫花苜蓿的生物量,抑制了叶片C、N、K和根系N、P和K的累积。M、R和RM处理均提高了干旱胁迫下紫花苜蓿的生物量,叶片C、N、P和K的含量,但却降低了根系N、P和K的含量。C/N对水分的响应较为不一致,但干旱胁迫提高了紫花苜蓿的叶片和根系的N/P和C/P。然而,M处理提高了干旱胁迫下紫花苜蓿叶片和根系的C/N、N/P和C/P。紫花苜蓿叶片和根系具有不同的代谢特征,所以其对AMF和水分具有不同的响应规律。此外,RM仅在对生物量和叶片N、P、K等方面具有较为明显的双接种协同增效的效益。本研究结果有助于进一步阐明共生体内C的消耗与N、P营养物质的转移之间的机制。

Effect of arbuscular mycorrhizal fungi on ecological stoichiometry characteristics of alfalfa under different water conditions

To evaluate the effect of arbuscular mycorrhizal fungi (AMF) on element contents and ecological stoichiometry of alfalfa (Medicago sativa) under drought and well-watered conditions,alfalfa plants inoculated with AMF (Glomus versiforme,M),rhizobia (Sinorhizobium meliloti,R),dual inoculation (RM),or no inoculations (CK) were evaluated in a pot experiment under controlled conditions.Organic carbon (C),nitrogen (N),phosphorus (P),and potassium (K) of plant leaves and roots were measured and ecological stoichiometric characteristics were calculated.The results showed that drought reduced the biomass of alfalfa and decreased the contents of C,N,and K in leaves and N,P,and K in roots.The M,R,and RM treatments improved the biomass of alfalfa and the contents of C,N,P,and K in leaves,but decreased the contents of N,P,and K in roots under drought.The response of C/N to water stress was not consistent,but drought improved N/P and C/P of alfalfa in leaves and roots.However,the M treatment increased C/N,N/P,and C/P of alfalfa in leaves and roots under drought condition.With different metabolic characteristics,alfalfa leaves and roots exhibited varied responses to AMF and different water availabilities.Moreover,there was no general synergistic effect of.dual inoculation with AMF and rhizobia on any parameter,except for the biomass and the contents of N,P,and K in leaves.All these results contribute to clarify the mechanism between consumption of C and transfer of N and P nutrition in symbiosis.