Regulation Of Arbuscular Mycorrhizal Fungi In Plant-Plant Interactions

Overyielding in intercropping is the main advantage compared to mono-cultivation, particularly in low-input and low fertility soils. Overyielding is mainly attributable to interspecific interactions. Arbuscular mycorrhizal fungi (AMF) is an important symbiotic microbes in the soil. They can form a symbiotic relationship with more than 80% of the terrestrial plants. Consequently mechanistic understanding of plant-plant interactions should consider the function of AMF. The present study was to understand the regulation of AMF in legume-cereal plant interactions. The role of AMF in the regulation of intraspecific and interspecific plant interactions and its influence on weeds was revealed. The dynamic process of biomass production and nutrient capture was investigated by using logistic models. Moreover, the influence soil microbials and P supply forms, and the effect of interactions between AMF and rhizobia on plant-plant interactions was explored. The main results are as following:(1) In the absence of AMF, maize, wheat, faba bean and foxtail growth were inhibited under P deficiency. Consequently the intensity of plant interactions was weaken. Inoculation with Funneliformis mosseae significantly enhanced the growth, and nutrient uptake (N and P) of mono-mazie, wheat, faba bean and foxtail. In the intercropping treatment (mazie/wheat/foxtail or faba bean/maize/foxtail), the presence of AMF and root intermingling facilitated plant interactions and enhanced intercropping overyielding. The growth of foxtail was greatly suppressed by AMF and/or roots interactions.(2) In uninoculated treatment, the maximum instantaneous biomass production of uninoculated wheat (0.303～0.396 g·d-1) is about 3-5 times compared to faba bean (0.081～0.093 g·d-1) plants in intercropping. When inoculation with Funneliformis mosseae, the maximum instantaneous biomass production of wheat and faba bean are 0.286～0.437 g-d-1 and 0.149～0.277 g·d-1 respectively. Compared to uninoculated treatments, inoculation did not significantly alter the time attaining the maximum instantaneous biomass and nutrient (N and P) capture of wheat plants. By contrast, the maximum instantaneous biomass and nutrient capture of inoculated faba bean delayed 2-9 d、11～16 d and 16～24 d separately. Wheat was less responsive to AMF. The inoculation with AMF mediated the competition between wheat/faba bean, and acted asymmetrically in favor of faba bean by substantially enhanced biomass production and nutrient acquisition. The temporal separation of N and P acquisition by competing plant species and enhancement of complementary resource use in the presence of AMF is attributable to the competitive co-existence of faba bean and wheat.(3) Soil microorganisms significantly inhibited the growth and uptake of N and P by wheat in the control treatment, and the decrease was 253.0、327.0 and 66.1% respectively. The application of sodium phytate and KH2PO4 increased the growth and nutrient uptake of wheat. The magnitude of microbial induced inhibition was reduced to 149.1,184.9 and 9.3% in sodium phytate treatment, and to 49.0,22.4 and 44.9% respectively in KH2PO4 treatment. The application of Ca10(OH)2(PO4)6 had no significant effect on wheat growth, but the maximum biomass was obtained in KH2PO4 treatment. Intercropping of wheat and faba bean could partly reduce the negative feedback of soil microorganisms on wheat plants. By contrast, soil microorganisms significantly promoted P uptake (31.3% on average) of faba bean plants. The growth of faba bean was not significantly affected by P forms. Wheat/faba bean intercropping had no significant influence on rhizosphere microbial community structure. Niche complementary of wheat and faba bean in terms of different P forms and different responses to soil microbials are likely attributable to overyielding in wheat/faba bean.(4) Sole inoculation with Funneliformis mosseae, Rhizobium leguminosarum or dual inoculation significantly promoted the growth and N and P uptake of wheat. Dual inoculation significantly increased the nodule number of faba bean roots. Inoculation with F. mosseae promoted the formation of the nodules and N fixation, and ultimately enhanced the growth of host and neighbouring plants, and the effect was greater in dual than in sole inoculation. In addition, faba bean facilitated interspecific interactions by promoting the release of organic acids and protons.