Abstract
The sex-specific physical and biochemical responses in dioecious plants to abiotic stresses could result in gender imbalance, and how to ease the current situation by microorganisms is still unclear. Using native soil where poplars were grown, growth parameters, soil physicochemical properties in the rhizosphere soil of different sexes of Populus cathayana exposed to salt stress and exogenous arbuscular mycorrhizal (AM) inoculation were tested. Besides, the sex-specific microbial community structures in the rhizosphere soil of different sexes of Populus cathayana were compared under salt stress. To identify the sex-specific microbial community characteristics related to salinity and AM symbiosis, a combined qPCR and DGGE method was used to monitor microbial community diversity. Seedlings suffered severe pressure by salt stress, reflected in limited growth, biomass, and nutrient element accumulation, especially on females. Exogenous AM inoculation treatment alleviated these negative effects, especially under salt treatment of 75 mM. Compared with salt effect, exogenous AM inoculation treatment showed a greater effect on soil physical–chemical properties of both sexes. Based on DGGE results, salt stress negatively affected fungal richness but positively affected fungal Simpson diversity index, while exogenous AM inoculation treatment showed the opposite effect. Structural equation modeling (SEM) was performed to show the causal relationships between salt and exogenous AM inoculation treatments with biomass accumulation and microbial community: salt and exogenous AM inoculation treatment showed complicated effects on elementary concentrations, soil properties, which resulted in different relationship with biomass accumulation and microbial community. Salt stress had a negative effect on soil properties and microbial community structure in the rhizosphere soil of P. cathayana, whereas exogenous AM inoculation showed positive impacts on most of the soil physical–chemical properties and microbial community status.
Highlights
Having an appropriate concentration of salt ions in the soil solution is very important for the completion of the normal plant life cycle; global periodic drought exacerbates soil salinization[1]
Among male seedlings under 0 mM condition, plants that received exogenous arbuscular mycorrhizal (AM) inoculation treatment showed more biomass and P content accumulation of the root than those did not, whereas no difference was detected in growth of stem length, P content of the leaf, N content of both the root and leaf between male seedlings received exogenous AM inoculation and those did not
growth rate of height (GRH) and P content of the leaf of seedlings inoculated by exogenous AM fungi were significantly higher than those recorded for uninoculated seedlings
Summary
Having an appropriate concentration of salt ions in the soil solution is very important for the completion of the normal plant life cycle; global periodic drought exacerbates soil salinization[1]. Bacteria and fungi in soil have been recognized as two important microbial populations that indicate soil health and productivity[7] These terrestrial microorganisms play a crucial role in ecological processes[8]. Few studies focus on how the microbial community structure in the rhizosphere soil of dioecious plants changes to salinity conditions and exogenous AM inoculation. With limited research on micro-organism’s variation in the rhizosphere soil of P. cathayana, we aimed to identify sex-specific responses in microbial community diversity to AM formation and salinity by nested PCR-DGGE a nalysis[13,14]. We examined two hypotheses in this study: i) Salt stress and exogenous AM inoculation would modify the rhizospheric environment of P. cathayana of both sexes. We examined two hypotheses in this study: i) Salt stress and exogenous AM inoculation would modify the rhizospheric environment of P. cathayana of both sexes. ii) Differences between the microbial communities from two genders to salt and AM inoculation would be detected
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