Effects Of Arbuscular Mycorrhizal Fungi On Phosphorus And Nitrogen Uptake Of Citrus

Arbuscular mycorrhize (AM) are symbiotic associations between the roots of crops and arbuscular mycorrhizal fungi. Previous reports revealed thet AM could improve resistance to drought, salt, humidity of hostd plant and protected them against extreme temperature and heavy metal stresses after AM had inoculated these host crops. Citrus is an important economic plant with good flavor and high level of vitamins, and with the development of the technology of AM, it will be to play an important role in improving of citrus quality and increasing of its production in future, as is beneficial for sustainable development of citrus industry in China and other countries. In order to know more intensive information about the potential of citrus arbuscular mycorrhizal fungi (AMF), herein, the seedlings of red tangerine (Citrus reticulate Blanco) and rough lemon (C. jambhiri Luch) was inoculated with different species of AM in pots, and we aimed at studying infection rate, the growth of the plants, and absorption of organic phosphorus (P) and nitrogen nutrition (N), and the probable reason that citrus AMF facilitated the absorption of P and N was also discussed in this paper. The main results obtained in this research are as follows:1. The seedlings of red tangerine and rough lemon can all be infected when they were inoculated with different species of AMF. Treatments with G.vm(a mixed fungal strains of Glomus versiforme and Gigaspora margarita) inoculation has the highest percentage of colonization, which is 97.09% for red tangerine; 81.08% for rough lemon; Glomus versiforme could infect red tangerine and rough lemon seedlings and the infection rate is 94.86% and 74.18% respectively; And the lowest infection rata occurred when red tangerine and rough lemon seedlings were inoculated with Gigaspora margarita, and only 55.17% for red tangerine, and 42.37% for rough lemon. These results suggested that all arbuscular mycorrhizal fungi adopted in this study all can infect red tangerine and rough lemon seedlings, and different infection rate exist in different AM.2. Arbuscular mycorrhizal fungi significantly increased the biomass of shoots and leaves, the length of stem space, the fresh weight of roots, leaf area, whole plants and content of chlorophyll a (b). Treatments with G.v.m strains inoculation generated the best result for red tangerine, but for rough lemon, infection of Gi. margarita gave rise to highest bioproductivity. Gl. versiforme was found to be the worst fungi stain for all the seedlings. 3. Inoculation AMF to red tangerine and rough lemon seedlings significantly increased the absoption of P from soil, and the content of P and P uptake of all of their leaves increased markedly. The same result was also found when investigating the content of P and P uptake of roots. Effect of different fungi strains on the content of P and P uptake is: G.v.m＞Gl. versiforme＞Gi. margarita.4. Inoculation AMF to red tangerine and rough lemon seedlings significantly increased the absoption of N from soil, and the content of N and N uptake of all of their leaves increased markedly. The same result was also found when investigating the content of N and N uptake of roots. Effect of different fungi strains on the content of N and N uptake is the same as that of organic P.5. Used seedlings without inoculation with AM as control (ck), we examined the rhizosphere soil acid phosphatase activities of red tangerine and rough lemon seedlings having AM infection, and the results are as follows: In the soil with normal content of P, inoculation AMF to red tangerine seedlings significantly increased the rhizosphere soil acid phosphatase activity, and the G.vm strain had the best effect, but in the soil absent of P, only Gi. margarita of the three strains has some effects on rhizosphere soil acid phosphatase activity; But for rough lemon, there was no markedly difference of the rhizosphere soil acid phosphatase activity beteen seedlings and ck in the soil absent of P, and even lower. In the soil with normal content of P, the rhizosphere soil acid phosphatase activity of rough lemon seedlings inoculated with AM was higher than that of ck markedly and especially inoculated with Gi. margarita.