Effects Of Arbuscular Mycorrhizal Fungi On Growths And High Temperature Tolerance Of Trifoliate Orange Seedlings

Arbuscular mycorrhize are symbiotic associations between roots and arbuscular mycorrhizal fungi. It can improve host plant for it's resistance to drought, salt, humidity and protect host plant against extreme temperature and heavy metal stresses. This research of mycorrhizae technique and its applications in citrus will contribute to the sustainable development of citrus industry in our country. The present work investigated the AM percentage of colonization and biotic production of trifoliate orange (Poncirus trifoliata (L.)Raf.) seedlings when they were inoculated with different arbuscular mycorrhizal fungi. The physiological and biochemical responses of host plants to fungi inoculation under different culture regimes were also investigated. The main results obtained in this experiment are as follows:1. Trifoliate orange seedlings can all be infected when they were inoculated with different species of arbuscular mycorrhizal fungi. Treatments with Gigspora margarita inoculation has the highest percentage of colonization, which is 85.7%; while Glomus versiforme could barely infect trifoliate orange seedlings and the infection rate is only 20.4%. Except mixed fungal strains(Gigspora margarita+ Glomus mosseae+ Glomus versiforme) and Gigspora margarita, the difference is significant in other treatment. The results in this experiment showed that all arbuscular mycorrhizal fungi can infect trifoliate orange seedlings.2. Arbuscular mycorrhizal fungi significantly increased the biomass of shoots and leaves, the length of stem internodes, the fresh weight of roots, leaves, and whole plants. And the seedlings inoculted with mixed fungal strains generated best results. These results indicate arbuscular mycorrhizal fungi can infect the trifoliate orange seedlings and significantly increase its bioproductivity after infection.3. Inoculation AFM to triofoliate orange seedlings increased the contents of soluble suger and soluble protein, activities of SOD and POD in the leaves of host plant stressed under 25℃, 30℃ and 40℃ respectively. The increased degrees are related to the inoculated AFM species, the order of the degrees from low to high is as Glomus versiforme, Glomus mosseae, Gigspora margarita and mixed fungal strains. Oppositely, same treatments as above decreased MDA and proline content, merbrane damage rates of the leaves. Inoculation AFM increased the root activity of trifoliate orange seedlings.4. According to the percentage of colonization, bilities for increasing biomass and high temperature tolerance, it can conclude that the dominant fungi strain for trifoliateorange seedings is Gigspora margarita .5. It can simply conclude that mycorrhizal trifoliate orange seedlings can resist the high temperature stress related to increasing its root activity.