Differences Of Root Traits And Mycorrhizal Responsiveness Of Winter Wheat Varieties Under Different Phosphorus Sources

Phosphorus(P),as a large number of elements in plants,plays an important role in plant growth and development.The root is one of the main ways to obtain P.Root structure,morphology,and physiological traits play an important role in the P efficiency of plants.Fully exploiting the characteristics of the root system of wheat is one of the effective methods to improve the absorption of P in the soil,and there is a large amount of AMF in the soil can form a symbiotic relationship with crops,and the mycorrhizal pathway formed can expand the exploration and absorption of phosphorus.In this paper,through pot experiment and field experiment method to study:(1)the traits and correlation strategies of above-and below-ground wheat with different P efficiencies at high and low phosphorus levels in the greenhouse were studied.(2)Three non-inorganic phosphorus levels,five organophosphorus levels and AMF inoculation were set to study the changes of wheat root traits and above-ground traits as well as the differences in mycorrhizal response of different varieties and the influencing factors.(3)Benzenes were added to the field to study the changes of root traits after mycorrhizal infection under natural conditions.The main conclusions are as follows:(1)Under the low phosphorus strip(0 mg·kg-1),the above-ground biomass,P content,P concentration,relative growth rate(RGR)and chlorophyll content of the high P efficiency varieties were significantly higher than those of the low P efficiency varieties.At low P levels,high P efficiency varieties has a smaller root length and lower root-to-root ratio low P efficiency varieties,but it has higher acid phosphatase activity,more fine root ratio,and smaller root diameter.Whether it is high P efficiency wheat or low P efficiency wheat,at low P phosphorus levels,the above-ground strategy of the plant is more relevant to the below-ground strategy;at high P levels(200 mg·kg-1),the correlation is more less,the trait changes above-ground and below-ground are relatively independent.(2)The addition of benomyl in the field experiment can significantly reduce the shoot dry weight and leaf area,the activity of acid phosphatase in rhizosphere soil,and reduce the root-shoot ratio,root dry weight and root diameter.The effects on root diameter and fine root ratio are not significant.The decline rate of infection rate of low P efficiency varieties is lower than that of high P efficiency varieties.(3)Under the condition of inorganic phosphorus,the low-molecular-weight organic acids secreted by wheat roots are mainly citric acid and tartaric acid.Inoculation with AMF will inhibit the secretion of low-molecular-weight organic acids in the rhizosphere,but it can significantly promote the activity of acid phosphatase activity.The presence of mycorrhiza significantly increased the shoot dry weight and leaf area,and the increase in the shoot dry weight reached an extremely significant at medium P level(50 mg·kg-1).However,the presence of mycorrhizal reduces the plasticity of root structural and morphological traits,but increases the plasticity of root physiological traits.The wheat showed the best infection rate and mycorrhizal responsiveness at medium phosphorus level after inoculation with AMF.And high P efficient wheat varieties showed a higher mycorrhizal dependence(4)Under organic P conditions,inoculation with AMF can significantly increase wheat dry weight,plant height and stem thickness,available P content of rhizosphere soil and phytase activity,but significantly reduce the leaf nitrogen(N)content.When the P level was 50 mg·kg-1,the shoot characteristic mycorrhizal response of all wheat varieties were maximized,and there were large differences among different wheat varieties.When the soil P level is relatively abundant(50-200 mg·kg-1),the wheat root structure and morphological traits are not sensitive to the response to AMF.When at low P level(0-20 mg·kg-1),AMF inoculation could increase the specific root length,root length and the root to shoot ratio.The optimal mycorrhizal responsiveness and infection rate were achieved for each variety with a P level of 50 mg·kg-1.The mycorrhizal response and infection rate were significantly different among wheat varieties,but the difference in infection rate was small.The Olsen-P content in rhizosphere has a good quadratic function relationship with phytase activity and infection rate,and the biomass mycorrhizal responsiveness shows a Gaussian function relationship with the increase of available phosphorus content in rhizosphere.Compared with inorganic P,there is a hysteresis effect on the infection rate and mycorrhizal response under organic P.The root length of wheat showed a negative effect on AMF under the condition of organic P,and a positive effect under the condition of inorganic P.The shoot dry weight showed the same pattern as that of inorganic P with the increase of organic P level.