低磷环境下接种丛枝菌根真菌促进紫花苜蓿生长和磷素吸收的机理

[目的]磷极易被土壤吸附和固定,导致土壤中磷有效性较低.研究接种丛枝菌根真菌(arbuscular mycorrhizal fungi,AMF)和低磷处理两者交互对紫花苜蓿生长和磷吸收的影响,为提高碱性土壤中磷肥利用率提供理论依据.[方法]以黄绵土和紫花苜蓿(Medicago sativa)为试验材料进行盆栽试验.在施...

Mechanisms of increasing alfalfa growth and phosphorus uptake by inoculation with arbuscular mycorrhizal fungal under low phosphorus application level

  【Objectives】  Phosphorus (P) is easily adsorbed and fixed by soil, resulting in low P availability in soil. This research investigated the interactive effects of AMF and low levels of P fertilizer on alfalfa growth and P-uptake to identify optimal methods for increasing P efficiency in alkaline soil.  【Methods】  A pot experiment was conducted using loessial soil and alfalfa (Medicago sativa) as test materials. The soil was treated with different P levels (0, 5 and 20 mg/kg, code as P0, P5, P20), and with AMF inoculation (20 g/L Glomus mosseae BGC YN02; +AMF) or without (–AMF). After 120 days of plant growth, the growth indices of alfalfa, P concentrations in alfalfa tissues, pH values, alkaline phosphatase activities, available P contents, and microbial biomass P in the rhizosphere and non-rhizosphere soil were analyzed. The composition and concentration of rhizosphere organic acids were also measured.  【Results】  In +AMF treatments, alfalfa roots were colonized by mycorrhiza, but P application rate had no significant effect on AMF root colonization. Both P application and AMF colonization significantly increased the dry mass and P concentrations of shoots and roots. The plant dry mass and P concentration in P20+AMF treatment were significantly higher than in the other treatments. The total amount of rhizosphere organic acids, especially citrate and acetate, in +AMF treatments decreased with increase in P application rate, but they were still significantly higher than those in ?AMF treatments. Phosphorus and AMF application significantly decreased soil alkaline phosphatase activity, but increased soil available-P and microbial biomass P contents. Alkaline phosphatase activity and microbial biomass P in rhizosphere were significantly higher than in non-rhizosphere. P20 trentment significantly decreased P-uptake efficiency and P-utilization efficiency, and +AMF significantly increased P-uptake efficiency.  【Conclusions】  AMF has a good symbiotic relationship with alfalfa roots in alkaline loessial soil. Low level of P application (≤ 20 mg/kg) has no significant effect on AMF root colonization. Both P application and AMF colonization could significantly stimulate the growth and P uptake of alfalfa. In low available P soil, inoculating AMF could broaden absorption area of root, increase alkaline phosphatase activity in rhizosphere and secretion of organic acids (especially citrate and acetate), and increase P-uptake efficiency.