The Effects Of AMF On Nitrogen Transfer And Physiology Of Male And Female Populus Cathayana In Low Nitrogen Environment

Both positive and negative interactions between plants are the most important factor for both construction of communities and maintenance of biodiversity.They determine population dynamics,community structure and ecosystem function.In recent years,the negative interaction between dioecious plants has been well reported,but the positive interaction between dioecious plants has been ignored.The transfer of nutrients in many active interaction types is the most direct one.In this experiment,applying stable isotopes(¹⁵NH₄)₂SO₄ as a tracer and Populus cathayana as a module,we followed the transport of N transfer via AMF in intersexual or intrasexual pairs.The content and mechanism of interaction between individuals of dioecious plants could be improved and a better N management strategies for a mixed plantation of dioecious plants could be given according to the consequences of this study.By comparing the differences in nitrogen transfer,morphological and physiological characteristics between male and female seedlings in four groups?CK,LN,AMF+NN,AMF+LN?,we get the main results were as follows:1.Differences in nitrogen transferInoculation with AMF and lower nitrogen level significantly increased the nitrogen transfer rate,nitrogen transfer amount,and%NDFT of M?F.And in the four groups,the nitrogen transfer rate,nitrogen transfer amount?except CK group?and%NDFT?except CK group?of F?M were significantly smaller than those of M?F.In addition,the net nitrogen transfer was-0.43 mg/plant,5.91 mg/plant,4.74 mg/plant and 14.29mg/plant in CK,LN,AMF+NN and AMF+LN groups,respectively.2.Differences in morphology and growthInoculation with AMF significantly increased the morphological and biomass accumulation.The growth rate of males were significantly higher than that of females.Second,nitrogen level also has a significant effect on morphology and biomass accumulation.In general,the aboveground morphology and biomass accumulation are on a downward trend under low nitrogen concentrations,while the root length and specific surface area are on a upward trend.In addition,the morphology and biomass accumulation of MF/M showed a decreasing trend compared with MM/M,while MF/F showed an increasing trend compared with FF/F.3.Differences in photosynthetic characteristics Inoculation with AMF significantly increased the net photosynthetic rate,and decreased the transpiration rate under normal nitrogen concentration.After inoculation,a lower nitrogen level significantly reduced net photosynthetic rate,intercellular CO₂.Before inoculation,the photosynthetic index of MM/M was significantly greater than FF/F,and after inoculation,MF/M was slightly larger than MF/F.In addition,the chlorophyll b and total chlorophyll of males were slightly larger than female plants in CK group,while females were significantly larger than males in LN group.And after inoculation,MM/M is greater than MF/M,MF/F is greater than FF/F.4.Differences in physiological indexesIn the four groups,males had smaller nitrate reductase than females.In addition,after inoculation,the root activity of males and females were significantly higher than before.The lower nitrogen level significantly decreased the root activity of the males and females in intersexual pairs and intrasexual.The root activity of MM/M is greater than MF/M,while FF/F is less than MF/F?except AMF+NN group?.In addition,Inoculation with AMF significantly increased the colonization rate of males and females.After inoculation,normal nitrogen concentration significantly promoted the infection of roots.Moreover,the colonization rate of females were significantly higher than that of males,except for males and females in intrasexual pairs of AMF+LN.5.Differences in carbon and nitrogen contentsInoculation with AMF significantly reduce the stem carbon content of MM/M at normal nitrogen level and MF/M at low nitrogen level.Before inoculation,a lower nitrogen level significantly increased the stem carbon content of MM/M,and after inoculation,a lower nitrogen level significantly increased the root carbon content of MF/M.In intrasexual pair,the root,stem and leaf carbon content of males were higher than that of female.In addition,inoculation of AMF significantly reduced the nitrogen content of roots,stems and leaves of females.After inoculation,the lower nitrogen level increased the nitrogen content of roots,stems and leaves of males and females.Compared with FF/F,MF/F has higher nitrogen content in those three parts.Moreover,the roots and stems nitrogen content of males were higher than that of females.These results indicated that:Firstly,there were two-way nitrogen transfer between male and female in different cultivation modes.The nitrogen transfer from male to female was weaker in CK group,weak in LN group,strong in AMF+NN group,and stronger in AMF+LN group.Second,the amount of net nitrogen transfer indicates that females are beneficiaries in LN,AMF+NN,and AMF+LN groups.In addition,according to those date,we found that AMF has a positive effect on MF/F and has a negative impact on MF/M in a low nitrogen environment.The content and mechanism of interaction between individuals of dioecious plants could be improved and a better N management strategies for a mixed plantation of dioecious plants could be given according to the consequences of this study.