Regulation Of Arbuscular Mycorrhizal Fungi And Phosphorus On Plant Lateral Root Formation And Involved Auxin Signaling Pathways

Roots are the plant organs for the absorption of water and nutrients from the soils,and act as the sensor probing the biotic and abiotic stresses.Root system architecture(RSA)is the configuration pattern of roots in the soil space,and the formation and the development of lateral roots are the most important factor controlling RSA.The length,branching angle,number of lateral root is mo st important index of RSA.RSA can be affected by many factors,such as biotic and abiotic factors.arbuscular mycorrhizal fungi(AMF)can affect several types of plants on RSA and its ecological significance has been emerging as a hotspot;P is essential mineral elements for plant which can also regulate plant lateral root development and there have been many research results;Auxin play a crucial part in plant lateral root development,it is the inner factor of lateral root development.In order to explore the arbuscular mycorrhizal fungi(AMF),P level and auxin on plant lateral root formation;investigate if AMF and P levels affect plant lateral root formation by auxin signal pathway and survey the different effect of(AMF),P level and auxin on different type of plant lateral root.In this study,citrus(Poncirus trifoliata(L.)Raf.),tomato(Solanum lycopersicum)and corn(Zea mays)were taken as experimental plants,and Rhizophagus irregularis as experimental AMF species.Use three factor randomized block design,there are AMF(M,NM),P level(HP,LP),auxin(IBA,TIBA,control).Based on these effects,the possible differential influencing patterns on RSA by AMF,P level,auxin was discussed through the comparisons between citrus and tomato or tomato and corn.The main findings are as follows:1.For citrus plants,AMF and HP significantly increase the plant biomass.TIBA significantly decreased the plant biomass.AMF stain decrease the main root length,increase the 1st and 2nd lateral root number,enhance the secondary lateral root formation ability;P level has no effect on the length of main root and lateral root formation;TIBA decrease the main root length and lateral root number.AMF and P level have significantly effects on the relative expression of lateral root and auxin transport gene,beside three are interaction between them.2.For tomato plants,AMF stain and HP both can increase the plant biomass;IBA and TIBA inhibit the growth of tomato seedlings.AMF stain can increase the number of 1st lateral root and 2nd lateral root,enhance the secondary lateral root formation ability at the same time.LP decrease the number of 1st and 2nd lateral root,but it enhance the secondary lateral root formation ability of tomato seedlings.IBA can promote the formation of lateral root while TIBA inhibit the formation of lateral root.In general,AMF and P level can both effect the gene relative expression during the lateral root formation of tomato seedlings.3.For corn plants,AMF stain decrease the plant biomass.HP increase the plant biomass.TIBA significantly decrease biomass of corn seedlings.AMF have different influence on different root type.AMF can effect almost all index of main root and seminal root.AMF just have influence on the lateral root formation ability of crown root.P level has no influence on main root,but it has influence on seminal and crown root.TIBA has negative effects on each type of root.4.Comparison between citrus and tomato indicates that the effects on the growth of woody plants and herb plants by AMF and phosphorus are consistent,both of them have positive effects on plant biomass.They can also change the RSA of plant through increase the proportion of fine lateral root.Leading to their similar effects on the root lateral root number.This suggests the diversity and complexity in the responding mechanisms of woody and herbs plants to AMF and P level.Comparison between tomato and corn indicates that the effects of AMF and phosphorus on the plant growth of cotyledon and monocots are consistent,showing a similar influencing pattern on the proportion of lateral roots but different patterns on lateral number.The mechanisms underlying it needs further study.