Responses Of Ectomycorrhizal Seedlings Root Of Pinus Massoniana To Drought Stress

Pinus massoniana is the most widely distributed, the highest degree of comprehensive utilization conifer species in our country, having fast-growing, high-yield, drought-resistant, easyupdating, and other excellent features. Furthermore, it is a typical ectotrophic mycorrhiza tree specie. Ectomycorrhizal fungi can improve the quality and drought resistance of seedlings. Combining with image scanning, topology, fractal dimension and other mathematical method were used to analysis effects of ectomycorrhizal fungi on root architecture, rhizosphere environment, and their responses to drought stress.Experiment used completely randomized design, set up two inoculated groups Sl12, Sl13 and one control group CK, four levels of water stress. Relative soil water content were normal water(65 ± 5)%, mild stress(45 ± 5)% moderate stress(30 ± 5)%, and severe stress(15 ± 5)%. The results showed that suillus luteus significantly promoted pinus massoniana seedlings height, diameter, biomass, root-shoot ratio and root vigor, and improved the quality of pinus massoniana seedlings. suillus luteus significantly increased the total length, surface area, volume of roots, number of root tips and lateral roots, extended lateral length, indicating that suillus luteus could expand root distribution space but did not change root branching strategy. Generally, suillus luteus improved the rhizosphere and non-rhizosphere soil catalase, invertase, urease and phosphatase activity, soil microbial population in varying degrees, and Sl13 better than Sl12.Suillus luteus significantly improved the biomass and root- shoot ratio at different water gradient conditions. The descending order of growth-promoting effects is normal≈mild> severe> moderate, root-shoot ratio is mild> moderate> severe ≈ normal, relationship mycorrhizal dependency is normal> mild > severe> moderate. Under mild drought stress, the mycorrhizal fungi can relatively maximum by raising the root-shoot ratio, assist the seedlings of moisture absorption process.Under moderate drought stress level, the survival of mycorrhizal fungi and the growth of the seedlings reached the state of relative balance, seedlings had the lowest relative mycorrhizal dependency. The excessive increase of drought stress pressure may lead to a drop in plant on root biomass and the influence of mycorrhizal fungi on the root-shoot ratio.As the increase of drought stress, the main root diameter and primary number of lateral roots decreases, the root extends to underground and reduces the distribution in the horizontal direction. Mycorrhizal seedlings could increase drought resistance of the plant by increasing the total length of root and root surface area, root volume and root number. Under normal water and mild drought stress, roots branch form of mycorrhizal seedlings did not change, the roots branch level increased. During severe drought stress, the branching pattern of mycorrhizal roots are more close to fishbone, to increase the relative depth of root system, the improvement on root extension become smaller.As the increase of drought stress strength, soil p H increases, soil enzyme activities and the number of culturable microorganism decrease. suillus luteus can improve seedling rhizosphere H+ concentration, soil enzyme activities and the number of culturable microorganisms at different levels.