| Ongoing global warming induced reducing rainfall leads to increased droughts and pest outbreaks in many parts of the world,which is seriously threatening the sustainability of agroforestry ecosystems.How to improve the insect resistance of plants under drought has become a hot issue.In recent years,many studies have found that different identities of neighbor could affect insect resistance of plants,and the effect in insect resistance defenses among neighbors are often mediated by the arbuscular mycorrhizal fungi(AMF).These studies are mainly based on different species or genotypes levels of neighbors in hermaphrodite,while relatively few studies have been conducted on the insect resistance of different sex neighbors in dioecious plant species,especially in arid habitats.In agroforestry,many plants are dioecious plants,and these often have important economic and ecological values.Therefore,in this text,Morus alba L.,an important agroforestry economic and ecological tree species in China,was chosen as the material.The differences in growth,leaf morphology,nutrients,secondary metabolites,and insect resistance performance of male and female mulberry seedlings under different moistures(simulated natural rainfall and half rainfall)by sex-related neighbors(no neighbors,intra-sexual neighbors and inter-sexual neighbors)were compared,and the AMF mediating effects were further analyzed.I tried to answer the following questions: Whether intra-sexual and inter-sexual neighbors differentially affect the insect resistance of female/male mulberry under drought? What are the effects of AMF mediated insect resistance of male and female mulberry under drought in different neighboring plants? The results of the study may not only provide new mechanisms to explore the effects of plant neighbors,but also provide countermeasures for ecological control of insect pests in mulberry plantations in the context of increasing global drought.The main findings are as follows:1.Effect of sex-related neighboring plants on insect feeding performance of male and female mulberry under droughtUnder drought,there were no significant sex differences in morphology,biomass,leaf elements,leaf defense material and insect feeding area between female and male plants in the presence of neighbors of different sexes.No significant differences were observed for female plants in the presence of intra-sexual neighbors or inter-sexual neighbors under drought compared to no neighbors,however,stem dry weight and total biomass were significantly lower for males in the presence of inter-sexual neighbors.For female plants,basal diameter,root dry weight and total biomass decreased in the absence of neighbors under drought compared to the control;basal diameter,root dry weight,total biomass,root to crown ratio,leaf C/N and leaf flavonoid content decreased significantly in the presence of inter-sexual neighbors,while leaf N content increased significantly.For male plants,compared to the control,basal diameter,total leaf area,stem weight,leaf dry weight,total biomass and leaf phosphorus content were significantly lower in the absence of neighbors under drought;root dry weight and leaf C/N were significantly lower in the presence of intra-sexual neighbors,while leaf nitrogen content,alkaloid content and DNJ content were significantly higher;total biomass and leaf C/N were significantly lower in the presence of inter-sexual neighbors,while leaf carbon content and The total biomass and leaf C/N decreased significantly in the presence of inter-sexual neighbors,while leaf carbon and alkaloid contents increased significantly.2.Effect of AMF mediated different sexual neighbors on the insect feeding performance of male and female mulberryUnder natural water inoculation with AMF,the root dry weight of female plants was significantly higher than that of male plants and the phosphorus content of male leaves was significantly higher than that of female plants in the absence of neighbors,and the leaf C/N of female plants was significantly higher than that of male plants in the presence of inter-sexual neighbors;the root dry weight of female plants was significantly higher than that of male plants in the presence of inter-sexual neighbors.Under homosexual neighbors,the basal diameter,stem dry weight,and total biomass of female plants were significantly lower,the leaf carbon content and insectivorous leaf area of male plants were significantly higher,and the leaf C/N of male plants was significantly lower,compared with no neighbors;under heterosexual neighbors,the leaf carbon content and insectivorous leaf area of female plants were significantly higher,the leaf carbon content and insectivorous leaf area of male plants were significantly higher,and the leaf C/N of male plants was significantly lower,compared with no neighbors.For female plants,root dry weight,total biomass,leaf phosphorus content,and leaf C/N were significantly higher,while leaf nitrogen content and insectivorous leaf area were significantly lower in the absence of neighbors compared with the absence of AMF inoculation;root dry weight,root to crown ratio,leaf phosphorus content,and leaf C/N were significantly higher,while leaf nitrogen content and alkaloid content were significantly lower in the presence of intra-sexual neighbors;plant height,root dry weight,and total In the presence of inter-sexual neighbors,plant height,root dry weight and total biomass were significantly higher,while leaf DNJ content was significantly lower.For male plants,total biomass,leaf phosphorus and leaf C/N were significantly higher and leaf insect-feeding leaf area was significantly lower in the absence of neighbors compared with the absence of AMF inoculation;leaf phosphorus and tannin contents were significantly higher and insect-feeding leaf area was significantly lower in the presence of intra-sexual neighbors;leaf flavonoid content was significantly higher and leaf alkaloids were significantly lower in the presence of inter-sexual neighbors.Under drought inoculation with AMF,after inoculation with AMF,there were no significant differences between female and male plants in morphology,leaf nutrients,leaf defense substances,and insect-feeding leaf area,except that the total leaf area of female plants was significantly higher than that of male plants when there were no neighbors;under intra-sexual neighbors,the insect-feeding leaf area of male plants was significantly higher than that of female plants,while under inter-sexual neighbors,there were no significant differences between female and male plants in insect-feeding area.Under intra-sexual neighbors,the total leaf area of female plants was significantly lower and the leaf alkaloid content was significantly higher compared to that of no neighbors,while the leaf alkaloid content of male plants was also significantly higher;under inter-sexual neighbors,the total leaf area,root dry weight,stem dry weight,leaf dry weight,total biomass and leaf C/N of female plants were significantly lower compared to that of no neighbors,while the leaf N and alkaloid content of female plants were significantly higher and the total phenol and DNJ of male plants were significantly higher.For female plants,compared with no AMF inoculation,female plant basal diameter,total leaf area,stem dry weight,total biomass and leaf C/N were significantly higher in the absence of neighboring plants,while female plant leaf nitrogen content,alkaloid content and insect-feeding leaf area were significantly lower;female plant basal diameter,root dry weight,total biomass and leaf C/N were significantly higher in the presence of intra-sexual neighbors,while female plant leaf nitrogen content and insect-feeding leaf area were significantly lower;the basal diameter of female plants was significantly higher in the presence of opposite sex neighbors.For male plants,root dry weight,leaf phosphorus content and leaf C/N were significantly higher in the absence of neighbors compared with the absence of AMF,while leaf contents of N and DNJ and insectivorous leaf area were significantly lower in males;leaf N and leaf alkaloid contents were significantly lower in the presence of inter-sexual neighbors,while leaf C/N,leaf phosphorus,and flavonoid contents were significantly higher in males.In summary,the insect resistance of mulberry leaves was affected by environmental water status and neighboring plants,however,the direction and intensity of the insect resistance effect of neighboring plants on both male and female plants under drought was related to the sex of the neighboring plants.Meanwhile,inoculation with AMF significantly increased defensive traits in both male and female mulberry leaves,and the effect of AMF in female plants were higher than male plants.Overall,drought altered the growth and insect resistance effects of neighboring plants on both male and female mulberry trees,and inoculation with AMF increased mulberry defenses against phytophagous insects.These results may investigate plant-neighbor relationships and provide new perspectives for the cultivation and management of mulberry plantations in the context of reduced global rainfall. |
PDF Full Text Request