| The paper studied the effect of the drought tolerance, growth and Phosphorus Utilization of alfalfa that was inoculated with differetn arbuscular mycorrhizal fungi that were examined in pot experiments. At the same time, a three compartment-cultivation system was designed to investigate the development of mycorrhizal network as mediated by the time effects, Medicago sativa, Dactylis glomerata and Bromus inermis Leyss as test plant were grown in two outer compartment, one as donor compartment receiving AM fungil inoculum and another as receiver compartment indicating development of hyphal network. We observed the biomass dynamics, production and turnover of the fine root of alfalfa by container method and minirhizotron in the whole growing season, the main reached the following conclusions: 1. The results showed that the underground biomass and infection rate of alfalfa were significantly increased that was inoculated with AM fungi under drought stress. The leaf water retention capacity of alfalfa and the content of soluble sugar, soluble protein were significantly increased after inoculating with AM fungi, but the content of malondialdehyde and proline were decreased, and the effect of drought tolerance of alfalfa was significantly difference that was inoculated with different AM fungi. It was suggest that AM fungi could improve plant water metabolism, the drought-resistant ability of alfalfa was enhanced that was inoculated the matching strains. Analysis the correlation between the indexes and drought resistance of alfalfa was showed that spore density> root dry weight>mycorrhizal infection rate> malondialdehyde aldehyde > soluble protein> soluble sugar >proline> water saturation deficit. 2. The experimental results indicated that: At 8 weeks after planting the external hyphas from donor plants penetrated the nylon meshes separating different compartments colonized Dactylis glomerata and Bromus inermis Leyss. The colonization of donor and receiver plants was different when they inoculated with different AM fungi species. At 14 weeks after planting, mycorrhizal colonization rate of receiver plants reached the same level as that of donor plants, however, the shoot and root biomass and the phosphorus concentrations were significant different, and the effect of biomass and P concentrations of alfalfa was outstanding difference that was inoculated with five AM fungi species. The study show that time was important factor influencing development of hyphal network between plant roots, and the established hyphal netwoek could promote the absorption of phosphorus. 3. The results showed that mixed inoculation treatment and G. mosseae colonized roots of alfalfa well and the colonization rate of mixed inoculation treatment was the highest. Inoculation of AM fungi promoted with the infection of root nodules, and increased colonization rate and root nodule numbers at the level of P60. The inoculation of alfalfa was significantly higher than non inoculated treatment in root dry weight, root length, plant height and the number of branches, with the dry weight of above increasing between 25.74% to 36.93%.At the same time, the dry weight of above and below ground as well as the number of branches was significantly higher in the level of P60 than in the P0 level. The absorption of phosphorus was enhanced with AM fungi inoculation, the phosphorus concentration of different parts of plant inoculation with mixed treatment(0.15-0.46%) and G. mosseae(0.16-0.36%) was significantly higher than that of control(0.11%-0.33%), the concentration of phosphorus in flowers was higher than other parts. There were significant effect on the dry weight above and belowground as well as on the stems, roots, leaves and the phosphorus content of soil, except for the root length, number of branches, plant height,the flower, the stems and lower stems in the interaction of the phosphorus level and inoculation with different AM fungi. 4. the experimental of fine root that was inoculated with AM fungi indicated that:(1)The inoculated Glomus mosseae(Gm)had the highest mean biomass(12.46 g·m-2), the control group had lowest mean biomass(7.31 g·m-2). The live fine root biomass peaked in mid September, but the dead showed a tendency of increasing first and then declining, and then increasing. In the whole growing process, the dead fine root biomass of non-inoculated was higher than inoculated treatment, and inoculated Glomus intraradices(Gi)showed the lowest biomass of dead fine root(3.11 g·m-2).(2) Inoculated Glomus etunicatum(Ge)had the highest fine root production(0.045 mcm·cm-2·d-1), Gm and control group had the lowest(0.027 mm·cm-2·d-1). However, fine root mortality of non-inoculated treatment(0.044 mm·cm-2·d-1) was significantly higher than inoculated treatments, and Gi had the lowest fine root mortality(0. 021 mm·cm-2·d-1).(3) Production and mortality peaks of fine roots appeared at the end of August and October, but trough came in at the end of September to mid October and the end of June to August during the growing reason. The average fine root length and annual length production of Glomus versiforme(Gv)was significantly higher than the control and other inoculated treatments. Control treatment had the highest fine root turnover, Gv and Gm were lowest.(4) the colonization rate, growth and the absorption of phosphorus were significant different inoculated with different AM fungi. Inoculation with AM fungi also decreased fine root turnover rates. Inoculation with a mixture of AM fungi species increased fine root turnover and P concentrations more than inoculation with a single AM fungi species, and could improve fine root biomass,reduce mortality and increase the lifespan of alfalfa. 5. In this paper, the methods of Principal Component Analysis, Membership Function Analysis, Grey Relational Analysis, and Fuzzy Similarity Priority Ratio Method were used to perform a comprehensive evaluation on the effects of inoculation with different arbuscular mycorrhizal fungi on alfalfa. Spore number, nodule number, colonization, soil phosphorus concentration, shoot phosphorus concentration, root phosphorus concentration, shoot dry weight, root dry weight, root length, branch number per plant, turnover, root length production, and root length mortality were used as indicators to constructed the model to evaluate the promoting effect of different AM fungi species on alfalfa. Four common evaluation models were used for different AM fungi species evaluations, and a comprehensive analysis was carried out on their evaluation results. The order from high to low is: 6G>Ge>Gm>Gi=Gv. |
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