The Effects Of Drought Stress And Root Exudates Exchange On Nitrogen Transfer Of Male And Female Populus Cathayana Rehd

In nature,plant-plant interactions can be either positive?facilitation?or negative?competition?.However,the neighboring plants may improve the utilization rate of resources by changing the relationship between them under drought stress.Nitrogen transfer was one of the ways to improve the resource utilization rate of adjacent plants,which can not only significantly improve the growth and development of neighbor plant,so as to improve the biomass,but enhance the adaptability of plants to drought stress.Nitrogen transfer between plants can be mediated by root exudates,so the exchange of root exudates will directly affect nitrogen transfer.Dioecious species are one of the important parts of terrestrial ecosystem,which are important for the stability of ecosystem structure and function.The previous studies showed the effects of drought stress on the growth and development of dioecious plants.Owing to the sex-related differences in reproductive effort,the growth of dioecious plants showed sexual dimorphism under drought stress.However,what is less clear is whether the growth and development of dioecious plants are affected by nitrogen transfer through the exchange of root exudates under drought stress.In this experiment,Populus cathayana was employed as a model species to study the effects of drought stress and root exudates exchange on the direction and intensity of nitrogen transfer in intra-and inter-sexual cultivation patterns of dioecious plants by the stable isotope ¹⁵N labeling method,so as to reveal the effects of soil water deficiency and root exudates exchange on the growth and development of dioecious plants.The results will provide a reference for further understanding the intrasexual and intersexual interaction process and mechanism of dioecious plants.The results were listed:1.Effects of drought stress and root exudates exchange on nitrogen transfer between male and female plants of P.cathayana under different sex cultivation patterns:Drought stress had a significant effect on the nitrogen transfer of male and female poplar plants.Root segregation with nylon mesh?root exudates exchange?significantly decreased the nitrogen transfer from male to female plants in intersexual cultivation patterns.Therefore,root exudates exchange had a significant effect on the nitrogen transfer of male and female poplar plants.Compared with the root segregation with plastic film?no contact?,root segregation with nylon mesh significantly increased the nitrogen transfer rate and%NDFT_don?%of N in donors derived from transfer?from male to female plants in intersexual cultivation patterns under well water condition?100%FC?.Similarly,root segregation with nylon mesh significantly increased the nitrogen transfer rate,nitrogen transfer amount,%NDFT?%of N in receiver derived from transfer?and%NDFT_donon from male to female plants in intersexual cultivation patterns under drought stress?30%FC?.Different sex cultivation patterns had a significant effect on the nitrogen transfer of male and female poplar plants.Compared with the root segregation with plastic film,both under well water?100%FC?and drought?30%FC?conditions,the nitrogen transfer rate,%NDFT and%NDFT_donon from males to females were significantly higher than those from female to male plants in intersexual cultivation patterns.In intersexual cultivation patterns,the amounts of net nitrogen transfer were 9.92 mg per plant and 3.83 mg per plant,respectively,and the direction of the transfer was from male to female plants.2.Effects of drought stress and root exudates exchange on morphology and biomass of P.cathayana males and females under different sex cultivation patterns:Drought stress significantly decreased the aboveground,root morphologies and biomass of plants.In root segregation with nylon mesh,the root morphology and biomass of female plants in intersexual cultivation patterns significantly decreased.However,in root segregation with plastic film,in intrasexual cultivation patterns,the root morphology and biomass of the female plants significantly decreased.Root exudates exchange had no significant effect on the aboveground morphology,root morphology and biomass of the plants.In intersexual cultivation patterns,the root morphology and biomass of the female plants in the root segregation with nylon mesh were higher than those in the root segregation with plastic film under well water condition.Different sex cultivation patterns also had an effect on the aboveground and root morphologies and biomass of plants.Compared with the root segregation with plastic film,the root morphology and biomass of the female plants were significantly higher than those of the male plants in intersexual cultivation patterns under well water condition.3.Effects of drought stress and root exudates exchange on plant gas exchange of P.cathayana males and females under different sex cultivation patterns:Drought stress significantly decreased the plant gas exchange.In root segregation with nylon mesh,the photosynthetic rate index of the female plants in intersexual cultivation patterns significantly decreased.In root segregation with plastic film,in intrasexual cultivation patterns,the photosynthetic rate index of the female plants significantly decreased.Root exudates exchange had no significant effect on the gas exchange.However,in intersexual cultivation patterns,the net photosynthetic rate of the male plants in root segregation with nylon mesh were lower than that in root segregation with plastic film under well water condition.In intersexual cultivation patterns,the net photosynthetic rate and transpiration rate of the female plants in root segregation with nylon mesh were lower than those in the root segregation with plastic film under drought stress.Different sex cultivation patterns had an effect on plant gas exchange.Compared with the root segregation with plastic film,the relative water content of the leaves and net photosynthetic rate of the male plants in intersexual cultivation patterns were the lowest under well water condition,the intercellular CO₂ was the highest of the female plants in intersexual cultivation patterns under drought stress.4.Effects of drought stress and root exudates exchange on physiological indexes of P.cathayana males and females under different sex cultivation patterns:Drought stress significantly decreased the leaf water potential of plants and increased the soluble sugar content and proline content of plants.In root segregation with plastic film,the proline content significantly increased and the leaf water potential significantly decreased in female plants in intersexual cultivation patterns.Root exudates exchange had a significant effect on the WUEi?instantaneous water use efficiency?of plants.Compared with the root segregation with plastic film,the WUEi of the male plants in intersexual cultivation patterns was significantly reduced under well water condition,however,the WUEi of male plants in intersexual cultivation patterns was significantly increased under drought stress.Different sex cultivation patterns had an effect on the physiological characteristics of the plants.Compared with the root segregation with plastic film,in intrasexual cultivation patterns,the WUEi and soluble sugar content of the female plants were the highest under well water condition,the WUEi of the male plants in intersexual cultivation patterns was the highest under drought stress.5.Effects of drought stress and root exudates exchange on carbon and nitrogen content of P.cathayana males and females under different sex cultivation patterns:Drought stress significantly decreased the content of carbon and nitrogen in root and stem of plants.In root segregation with plastic film,the carbon and nitrogen contents of the leaves and stems of the female plants in intrasexual cultivation patterns significantly decreased.In the root segregation with plastic film,the leaf carbon and nitrogen content of the female plants in intrasexual cultivation patterns significantly decreased.Root exudates exchange had no significant effect on the carbon and nitrogen content of plants.Different sex cultivation patterns had a significant effect on the content of carbon and nitrogen in root of plants.Compared with the root segregation with plastic film,the content of nitrogen in stem of male plants in intersexual cultivation patterns was the lowest under drought stress.The above results showed that there was a bidirectional nitrogen transfer between male and female plants in the intra-and inter-sexual cultivation patterns.In root segregation with nylon mesh,in intersexual cultivation patterns,the amounts of net nitrogen transfer were 9.92 mg per plant and 3.83 mg per plant under well water and drought conditions,respectively,and the female plants were the ultimate beneficiaries of nitrogen transfer.In addition,according to other data from the plants,we find that some nitrogen transfer was mediated by the root exudates under drought stress and the growth and development of female plants was promoted.The relationship and content of interaction of dioecious plants were improved under drought stress and some references for the value of mixed planting of dioecious plants were provided by the results of this experiment.