Application of Zinc Oxide Nanoparticles to Mitigate Cadmium Toxicity: Mechanisms and Future Prospects.

Cadmium (Cd), as the most prevalent heavy metal contaminant poses serious risks to plants, humans, and the environment. The ubiquity of this toxic metal is continuously increasing due to the rapid discharge of industrial and mining effluents and the excessive use of chemical fertilizers. Nanoparticles (NPs) have emerged as a novel strategy to alleviate Cd toxicity. Zinc oxide nanoparticles (ZnO-NPs) have become the most important NPs used to mitigate the toxicity of abiotic stresses and improve crop productivity. The plants quickly absorb Cd, which subsequently disrupts plant physiological and biochemical processes and increases the production of reactive oxygen species (ROS), which causes the oxidation of cellular structures and significant growth losses. Besides this, Cd toxicity also disrupts leaf osmotic pressure, nutrient uptake, membrane stability, chlorophyll synthesis, and enzyme activities, leading to a serious reduction in growth and biomass productivity. Though plants possess an excellent defense mechanism to counteract Cd toxicity, this is not enough to counter higher concentrations of Cd toxicity. Applying Zn-NPs has proven to have significant potential in mitigating the toxic effects of Cd. ZnO-NPs improve chlorophyll synthesis, photosynthetic efficiency, membrane stability, nutrient uptake, and gene expression, which can help to counter toxic effects of Cd stress. Additionally, ZnO-NPs also help to reduce Cd absorption and accumulation in plants, and the complex relationship between ZnO-NPs, osmolytes, hormones, and secondary metabolites plays an important role in Cd tolerance. Thus, this review concentrates on exploring the diverse mechanisms by which ZnO nanoparticles can alleviate Cd toxicity in plants. In the end, this review has identified various research gaps that need addressing to ensure the promising future of ZnO-NPs in mitigating Cd toxicity. The findings of this review contribute to gaining a deeper understanding of the role of ZnO-NPs in combating Cd toxicity to promote safer and sustainable crop production by remediating Cd-polluted soils. This also allows for the development of eco-friendly approaches to remediate Cd-polluted soils to improve soil fertility and environmental quality.

The effect of winter crop incorporation on greenhouse gas emissions from double rice-green manure rotation in South China.

Chemical fertilizer plays a vital role in increasing crop yield. However, the environmental risk and the adverse effect on soil caused by excessive chemical fertilizer can be mitigated by using organic fertilizer (green manure Chinese milk vetch) and straw returning. Therefore, this field study was conducted to determine the impact of winter crop incorporation with mineral fertilizers on methane (CH4) and nitrous oxide (N2O) emissions and the related genes (mcrA, pmoA, AOA, AOB, nirS, nirK, and nosZ) as well as the relationship among greenhouse gas (GHG) emissions, related genes, and soil properties. The study comprised winter crop incorporation with mineral fertilizer at the reduced rate of 0% (MRN1), 12.5% (MRN2), and 25% (MRN3). The results indicated that the early and late rice yield from treatments MRN2 and MRN3 increased by 25% and 4% compared with control CK (winter fallow, without green manure incorporation, and conventional nitrogen fertilizer amount). CH4 annual cumulative emission increased by 34% resulting from increased abundance of mcrA genes of methanogens. Furthermore, N2O annual cumulative emission increased due to soil microbial biomass nitrogen, AOA (amoA), AOB(amoA), nirK, and nirS abundance. The global warming potential (GWP) increased by 34%; however, there was no significant difference on the GHGI from all the treatments resulting from the increased yield. Therefore, winter crop incorporation with different rate of reduced mineral fertilizer significantly increased the crop yield and increased the SOC and MBC content. Meanwhile, winter crop incorporation increased CH4 and N2O annual cumulative emission mainly resulting from the increased abundance of mcrA genes of methanogens, soil microbial biomass nitrogen, AOA(amoA), AOB(amoA), nosZ, nirK, and nirS abundance.

Soil acidification and salinity: the importance of biochar application to agricultural soils.

Soil acidity is a serious problem in agricultural lands as it directly affects the soil, crop production, and human health. Soil acidification in agricultural lands occurs due to the release of protons (H+) from the transforming reactions of various carbon, nitrogen, and sulfur-containing compounds. The use of biochar (BC) has emerged as an excellent tool to manage soil acidity owing to its alkaline nature and its appreciable ability to improve the soil's physical, chemical, and biological properties. The application of BC to acidic soils improves soil pH, soil organic matter (SOM), cation exchange capacity (CEC), nutrient uptake, microbial activity and diversity, and enzyme activities which mitigate the adverse impacts of acidity on plants. Further, BC application also reduce the concentration of H+ and Al3+ ions and other toxic metals which mitigate the soil acidity and supports plant growth. Similarly, soil salinity (SS) is also a serious concern across the globe and it has a direct impact on global production and food security. Due to its appreciable liming potential BC is also an important amendment to mitigate the adverse impacts of SS. The addition of BC to saline soils improves nutrient homeostasis, nutrient uptake, SOM, CEC, soil microbial activity, enzymatic activity, and water uptake and reduces the accumulation of toxic ions sodium (Na+ and chloride (Cl-). All these BC-mediated changes support plant growth by improving antioxidant activity, photosynthesis efficiency, stomata working, and decrease oxidative damage in plants. Thus, in the present review, we discussed the various mechanisms through which BC improves the soil properties and microbial and enzymatic activities to counter acidity and salinity problems. The present review will increase the existing knowledge about the role of BC to mitigate soil acidity and salinity problems. This will also provide new suggestions to readers on how this knowledge can be used to ameliorate acidic and saline soils.

Efficient Adsorption and Electrochemical Detection of Cd2+ with a Ternary MgZnFe-Layered Double Hydroxides Engineered Porous Biochar Composite.

Their unique layered structure, large specific surface area, good stability, high negative charge density between layers, and customizable composition give layered double hydroxides (LDHs) excellent adsorption and detection performance for heavy metal ions (HMIs). However, their easy aggregation and low electrical conductivity limit the practical application of untreated LDHs. In this work, a ternary MgZnFe-LDHs engineered porous biochar (MgZnFe-LDHs/PBC) heterojunction was proposed as a sensing and adsorption material for the effective detection and removal of Cd2+ from wastewater. The growth of MgZnFe-LDHs in the PBC pores not only reduces the accumulation of MgZnFe-LDHs, but also improves the electrical conductivity of the composite. The synergistic effect between MgZnFe-LDHs and PBC enables the composite to achieve a maximum adsorption capacity of up to 293.4 mg/g for Cd2+ in wastewater. Meanwhile, the MgZnFe-LDHs/PBC-based electrochemical sensor shows excellent detection performance for Cd2+, presenting a wide linear range (0.01 ng/L-1 mg/L), low detection limit (3.0 pg/L), good selectivity, and stability. The results indicate that MgZnFe-LDHs/PBC would be a potential material for detecting and removing Cd2+ from wastewater.

The Influence of Heat Treatment Temperature on Tensile Properties of Metal-Bonded Diamond Composites Fabricated via Selective Laser Melting.

Selective Laser Melting (SLM) is an effective technology for fabricating new types of porous metal-bonded diamond tools with complex geometries. However, due to the high cooling rate and internal stresses during SLM fabrication, defects such as high porosities and interface gaps still need to be resolved before it can be considered for use in other applications. The influence of heat treatment temperature on internal characterization, interface microstructures, and tensile properties of AlSi7Mg-bonded diamond composites fabricated by SLM were investigated in this work. From experimental results, the porosities of HT-200, HT-350, and HT-500 specimens were 12.19%, 11.37%, and 11.14%, respectively, showing a slightly lower percentage than that of the No-HT specimen (13.34%). Here, HT represents "Heat Treatment". For No-HT specimens, an obvious un-bonding area can be seen in the interface between AlSi7Mg and diamond, whereas a relative closer interface can be observed for HT-500 specimens. After heat treatment, the elastic modulus of specimens showed a relative stable value (16.77 ± 2.79~18.23 ± 1.72 GPa), while the value of yield strength decreased from 97.24 ± 4.48 to 44.94 ± 7.06 MPa and the value of elongation increased from 1.98 ± 0.05 to 6.62 ± 0.51%. This difference can be attributed mainly to the disappearance of the solid-solution hardening effect due to the increase of Si content after heat treatment.

Investigation of the Fabrication of Diamond/SiC Composites Using α-Si3N4/Si Infiltration.

Diamond/SiC (Dia/SiC) composites possess excellent properties, such as high thermal conductivity and low thermal expansion coefficient. In addition, they are suitable as electronic packaging materials. This study mainly optimized the diamond particle size packing and liquid-phase silicon infiltration processes and investigated a method to prevent the adhesion of the product to molten silicon. Based on the Dinger-Funk particle stacking theory, a multiscale diamond ratio optimization model was established, and the volume ratio of diamond particles with sizes of D20, D50, and D90 was optimized as 1:3:6. The method of pressureless silicon infiltration and the formulas of the composites were investigated. The influences of bedding powder on phase composition and microstructure were studied using X-ray diffraction and scanning electron microscopy, and the optimal parameters were obtained. The porosity of the preform was controlled by regulating the feeding amount through constant volume molding. Dia/SiC-8 exhibited the highest density of 2.73 g/cm3 and the lowest porosity of 0.6%. To avoid adhesion between the sample and buried powder with the bedding silicon powder, a mixed powder of α-Si3N4 and silicon was used as the buried powder and the related mechanisms of action were discussed.

How Does Zinc Improve Salinity Tolerance? Mechanisms and Future Prospects.

Salinity stress (SS) is a serious abiotic stress and a major constraint to agricultural productivity across the globe. High SS negatively affects plant growth and yield by altering soil physio-chemical properties and plant physiological, biochemical, and molecular processes. The application of micronutrients is considered an important practice to mitigate the adverse effects of SS. Zinc (Zn) is an important nutrient that plays an imperative role in plant growth, and it could also help alleviate the effects of salt stress. Zn application improves seed germination, seedling growth, water uptake, plant water relations, nutrient uptake, and nutrient homeostasis, therefore improving plant performance and saline conditions. Zn application also protects the photosynthetic apparatus from salinity-induced oxidative stress and improves stomata movement, chlorophyll synthesis, carbon fixation, and osmolytes and hormone accumulation. Moreover, Zn application also increases the synthesis of secondary metabolites and the expression of stress responsive genes and stimulates antioxidant activities to counter the toxic effects of salt stress. Therefore, to better understand the role of Zn in plants under SS, we have discussed the various mechanisms by which Zn induces salinity tolerance in plants. We have also identified diverse research gaps that must be filled in future research programs. The present review article will fill the knowledge gaps on the role of Zn in mitigating salinity stress. This review will also help readers to learn more about the role of Zn and will provide new suggestions on how this knowledge can be used to develop salt tolerance in plants by using Zn.

Direct-Drive Electro-Hydraulic Servo Valve Performance Characteristics Prediction Based on Big Data and Neural Networks.

Direct-drive electro-hydraulic servo valves play a key role in aerospace control systems, and their operational stability and safety reliability are crucial to the safety, stability, and efficiency of the entire control system. Based on the prediction of the performance change of the servo valve and the resulting judgement and prediction of its life, this can effectively avoid serious accidents and economic losses caused by failure due to performance degradation in the work. On the basis of existing research, factors such as opening, oil contamination, and pressure difference are used as prerequisites for the operation of direct-drive electro-hydraulic servo valves. In addition to the current research on pressure gain and leakage, the performance parameters of servo valves, such as overlap, threshold, and symmetry, are also expanded and selected as research objects, combined with pressure design servo valve performance degradation experiments for testing instruments such as flow and position sensors, and data are obtained on changes in various performance parameters. The experimental data are analyzed and a prediction model is built to predict the performance parameters of the servo valve by combining the existing popular neural networks, and the prediction error is calculated to verify the accuracy and validity of the model. The experimental results indicate that as the working time progresses, the degree of erosion and wear on the valve core and valve sleeve of the servo valve increases. Overall, it has been observed that the performance parameters of the servo valve show a slow trend of change under different working conditions, and the rate of change is generally higher under high pollution (level 9) conditions than under other conditions. The prediction results indicate that the predicted values of various performance parameters of the servo valve by the prediction model are lower than 0.2% compared to the experimental test set data. By comparing the two dimensions of the accuracy and prediction trend, this model meets industrial needs and outperforms deep learning algorithm models such as the exponential smoothing algorithm and ARIMA model. The experiments and results of this study provide theoretical support for the life prediction model of servo valves based on neural networks and machine learning in artificial intelligence, and provide a reference for the development of direct-drive electro-hydraulic servo valves in aerospace and other industrial fields for use and failure standards.

Dependence of Monocrystalline Sapphire Dicing on Crystal Orientation Using Picosecond Laser Bessel Beams.

Dicing is a critical step in the manufacturing process for the application of sapphire. In this work, the dependence of sapphire dicing on crystal orientation using picosecond Bessel laser beam drilling combined with mechanical cleavage was studied. By using the above method, linear cleaving with on debris and zero tapers was realized for the A1, A2, C1, C2, and M1 orientations, except for the M2 orientation. The experimental results indicated that characteristics of Bessel beam-drilled microholes, fracture loads, and fracture sections of sapphire sheets were strongly dependent on crystal orientation. No cracks were generated around the micro holes when laser scanned along the A2 and M2 orientations, and the corresponding average fracture loads were large, 12.18 N and 13.57 N, respectively. While along the A1, C1, C2, and M1 orientations, laser-induced cracks extended along the laser scanning direction, resulting in a significant reduction in fracture load. Furthermore, the fracture surfaces were relatively uniform for A1, C1, and C2 orientations but uneven for A2 and M1 orientations, with a surface roughness of about 1120 nm. In addition, curvilinear dicing without debris or taper was achieved to demonstrate the feasibility of Bessel beams.

nirS and nosZII bacterial denitrifiers as well as fungal denitrifiers are coupled with N2O emissions in long-term fertilized soils.

Fertilizer application plays a critical role in soil fertility and crop yield and has been reported to significantly affect soil denitrification. However, the mechanisms by which denitrifying bacteria (nirK, nirS, nosZI, and nosZII) and fungi (nirK and p450nor) affect soil denitrification are poorly understood. Therefore, in this study, we investigated the effect of different fertilization treatments on the abundance, community structure, and function of soil denitrifying microorganisms in an agricultural ecosystem with long-term fertilization using mineral fertilizer or manure and their combination. The results showed that the application of organic fertilizer significantly increased the abundance of nirK-, nirS-, nosZI-, and nosZII-type denitrifying bacteria as the soil pH and phosphorus content increased. However, only the community structure of nirS- and nosZII-type denitrifying bacteria was influenced by the application of organic fertilizer, which led to a higher contribution of bacteria to nitrous oxide (N2O) emissions than that observed after inorganic fertilizer application. The increase in soil pH reduced the abundance of nirK-type denitrifying fungi, which may have presented a competitive disadvantage relative to bacteria, resulting in a lower contribution of fungi to N2O emissions than that observed after inorganic fertilizer application. The results demonstrated that organic fertilization had a significant impact on the community structure and activity of soil denitrifying bacteria and fungi. Our results also highlighted that after organic fertilizer application, nirS- and nosZII-denitrifying bacteria communities represent likely hot spots of bacterial soil N2O emissions while nirK-type denitrifying fungi represent hot spots for fungal soil N2O emissions.

Pelvic floor dysfunction and electrophysiology in postpartum women at 6-8 weeks.

Objective: To investigate the incidence of pelvic floor dysfunction (PFD) and electrophysiological indicators in postpartum women at 6-8 weeks and explore the influence of demographic characteristics and obstetric factors. Methods: A survey questionnaire collected information about the conditions of women during their pregnancy and puerperal period and their demographic characteristics; pelvic organ prolapse quantitation (POP-Q) and pelvic floor muscle electrophysiology (EP) examination were conducted in postpartum women at 6-8 weeks. Results: Vaginal delivery was a risk factor for anterior pelvic organ prolapse (POP) (OR 7.850, 95% confidence interval (CI) 5.804-10.617), posterior POP (OR 5.990, 95% CI 3.953-9.077), anterior and posterior stage II POP (OR 6.636, 95% CI 3.662-15.919), and postpartum urinary incontinence (UI) (OR 6.046, 95% CI 3.894-9.387); parity was a risk factor for anterior POP (OR 1.397,95% CI 0.889-2.198) and anterior and posterior stage II POP (OR 4.162, 95% CI 2.125-8.152); age was a risk factor for anterior POP (OR 1.056, 95% CI 1.007-1.108) and postpartum UI (OR 1.066, 95% CI 1.014-1.120); body mass index (BMI) was a risk factor for postpartum UI (OR 1.117, 95% CI 1.060-1.177); fetal birth weight was a risk factor for posterior POP (OR 1.465, 95% CI 1.041-2.062); and the frequency of pregnancy loss was a risk factor for apical POP (OR 1.853, 95% CI 1.060-3.237). Conclusion: Pelvic floor muscle EP is a sensitive index of early pelvic floor injury. The changes in muscle strength and fatigue degree coexist in different types of postpartum PFD, and each has its own characteristics.

Properties Evaluations of Topology Optimized Functionally Graded Lattice Structures Fabricated by Selective Laser Melting.

Owning to their lightweight characteristic and high performance, functionally graded lattice structures (FGLSs) show great potential in orthopedics, automotive industries and aerospace applications. Here, two types of uniform lattice structures (ULSs) with RD = 0.50 and 0.20, and two types of FGLSs with RD = 0.30-0.50 and RD = 0.20-0.40, were designed by topology optimization and fabricated by SLM technology. Subsequently, their surface morphology, compressive deformation behavior and energy absorption abilities were evaluated by use of the finite element method (FEM) and compression tests. From these results, both elastic modulus and yield strength of specimens decreased with the lowering of the RD value. ULSs had a uniform deformation behavior with bending and bulking of struts, while FGLSs presented a mixed deformation behavior of different layers. Additionally, the energy absorption capability (Wv) of specimens was proportional to the RD value. When the value of RD increased from 0.20 to 0.50, the Wv of specimens increased from 0.3657 to 1.7469 MJ/m3. Furthermore, mathematical models were established successfully to predict the mechanical properties of FGLSs with percentage deviations < 10%. This work provides a comprehensive understanding regarding how to design and manufacture FGLSs with the properties desired for satisfying the demand of different application scenarios.

Acceptance of Smart Technologies in Blended Learning: Perspectives of Chinese Medical Students.

Smart technologies are essential in improving higher education teaching and learning. The present study explores the factors that influence students' behavioural intentions to adopt and use smart technologies in blended learning. Based on the Unified Theory of Acceptance and Use of Technology (UTAUT2) model, a survey of 305 students was conducted to collect data. A structural equation model was applied to analyse the data. The findings show that adopting smart technologies requires appropriate social context and organizational support. Moreover, the data indicated that performance expectancy, effort expectancy, social influence, hedonic motivation, and habit are vital in determining students' behavioural intention to use smart technologies. However, facilitating conditions and price value were found to have no significant impact on the students' behavioural intention to use smart technologies. The study contributes to a better understanding of the nexus of blended learning and smart technologies, thus improving students' experiences in blended learning settings.

Winter crop rotation intensification to increase rice yield, soil carbon, and microbial diversity.

Crop rotation has widely contributed to increasing farmland biodiversity as well as to improving soil carbon pools and microbial diversity. However, there is a weak understanding of the suitability of winter crop rotation intensification in double rice fields, especially rotation with various winter crops. For this task, a long-term field experiment based on one from 2012 was conducted with five winter crop systems for double rice: winter fallow (T0), winter milk vetch (T1), winter rape (T2), winter garlic (T3), winter rotation intensification with potato, milk vetch, and rape (T4). Parameters such as crop yield, soil carbon, nitrogen, and soil microorganism were measured. It was found that compared to winter fallow, winter milk vetch, rape, garlic, and crop rotation intensification practices increased the late rice yield by 2.5%, 2.3%, 4.5%, and 3.7%, respectively; winter garlic and crop rotation intensification also increased the early rice yield by 4.6% and 3.5%, respectively. This is associated with the promotion of rice tillering. At the same time, for winter crop rotation, compared to winter fallow, the soil organic carbon increased by 21%. With the input of diversified crop residues, winter crops were effective in soil carbon sequestration, improving soil microbial structure, and increasing soil microbial diversity. The Shannon diversity index of winter crops ranged from 9.75 to 9.91, while winter fallow was 9.38. The Simpson's diversity index of winter crops ranged from 0.997 to 0.998, while winter fallow was 0.996. In conclusion, winter crop practices, especially winter crop rotation intensification, can enhance soil health and sustainability in double rice fields through its positive feedback on crop yield, soil carbon sequestration, and microorganisms.

In Situ Synthesis of MnMgFe-LDH on Biochar for Electrochemical Detection and Removal of Cd2+ in Aqueous Solution.

Herein, MnMgFe-layered double hydroxides/biochar (MnMgFe-LDHs/BC) composite was fabricated by immobilizing MnMgFe-LDHs on BC via the coprecipitation method, which was employed as an effective material for the detection and removal of Cd2+ from aqueous media. A lamellar structure of MnMgFe-LDHs with abundant surface-hydroxyl groups and various interlayer anions inside present a greater chance of trapping Cd2+. Meanwhile, the conductive BC with a porous structure provides numerous channels for the adsorption of Cd2+. Using the MnMgFe-LDHs/BC-based sensor, Cd2+ can be detected with a low limit of detection down to 0.03 ng/L. The feasibility of detecting Cd2+ in paddy water was also carried out, with satisfactory recoveries ranging from 97.3 to 102.3%. In addition, the MnMgFe-LDHs/BC material as an adsorbent was applied to remove Cd2+ from water with adsorption capacity of 118 mg/g, and the removal efficiency can reach 91%. These results suggest that the as-prepared MnMgFe-LDHs/BC can serve as a favorable platform for efficient determination and removal of Cd2+ in water.

Toxic effects of antimony in plants: Reasons and remediation possibilities-A review and future prospects.

Antimony (Sb) is a dangerous heavy metal (HM) that poses a serious threat to the health of plants, animals, and humans. Leaching from mining wastes and weathering of sulfide ores are the major ways of introducing Sb into our soils and aquatic environments. Crops grown on Sb-contaminated soils are a major reason of Sb entry into humans by eating Sb-contaminated foods. Sb toxicity in plants reduces seed germination and root and shoot growth, and causes substantial reduction in plant growth and final productions. Moreover, Sb also induces chlorosis, causes damage to the photosynthetic apparatus, reduces membrane stability and nutrient uptake, and increases oxidative stress by increasing reactive oxygen species, thereby reducing plant growth and development. The threats induced by Sb toxicity and Sb concentration in soils are increasing day by day, which would be a major risk to crop production and human health. Additionally, the lack of appropriate measures regarding the remediation of Sb-contaminated soils will further intensify the current situation. Therefore, future research must be aimed at devising appropriate measures to mitigate the hazardous impacts of Sb toxicity on plants, humans, and the environment and to prevent the entry of Sb into our ecosystem. We have also described the various strategies to remediate Sb-contaminated soils to prevent its entry into the human food chain. Additionally, we also identified the various research gaps that must be addressed in future research programs. We believe that this review will help readers to develop the appropriate measures to minimize the toxic effects of Sb and its entry into our ecosystem. This will ensure the proper food production on Sb-contaminated soils.

CFD-Based Physical Failure Modeling of Direct-Drive Electro-Hydraulic Servo Valve Spool and Sleeve.

Direct-drive electro-hydraulic servo valves are used extensively in aerospace, military and control applications, but little research has been conducted on their service life and physical failure wear. Based on computational fluid dynamics, the main failure forms of direct-drive electro-hydraulic servo valves are explored using their continuous phase flow and discrete phase motion characteristics, and then combined with the theory of erosion for calculation. A mathematical model of the direct-drive electro-hydraulic servo valve is established by using Solidworks software, and then imported into Fluent simulation software to establish its physical failure model and carry out simulation. Finally, the physical failure form of the direct drive electro-hydraulic servo valve is verified by the simulation results, and the performance degradation law is summarized. The results show that temperature, differential pressure, solid particle diameter and concentration, and opening degree all have an impact on the erosion and wear of direct-drive electro-hydraulic servo valves, in which differential pressure and solid particle diameter have a relatively large impact, and the servo valve must avoid working in the range of high differential pressure and solid particle diameter of 20-40 um as far as possible. This also provides further theoretical support and experimental guidance for the industrial application and life prediction of electro-hydraulic servo valves.

Versatile roles of polyamines in improving abiotic stress tolerance of plants.

In recent years, extreme environmental cues such as abiotic stresses, including frequent droughts with irregular precipitation, salinity, metal contamination, and temperature fluctuations, have been escalating the damage to plants' optimal productivity worldwide. Therefore, yield maintenance under extreme events needs improvement in multiple mechanisms that can minimize the influence of abiotic stresses. Polyamines (PAs) are pivotally necessary for a defensive purpose under adverse abiotic conditions, but their molecular interplay in this remains speculative. The PAs' accretion is one of the most notable metabolic responses of plants under stress challenges. Recent studies reported the beneficial roles of PAs in plant development, including metabolic and physiological processes, unveiling their potential for inducing tolerance against adverse conditions. This review presents an overview of research about the most illustrious and remarkable achievements in strengthening plant tolerance to drought, salt, and temperature stresses by the exogenous application of PAs. The knowledge of underlying processes associated with stress tolerance and PA signaling pathways was also summarized, focusing on up-to-date evidence regarding the metabolic and physiological role of PAs with exogenous applications that protect plants under unfavorable climatic conditions. Conclusively, the literature proposes that PAs impart an imperative role in abiotic stress tolerance in plants. This implies potentially important feedback on PAs and plants' stress tolerance under unfavorable cues.

Impacts of Rotation-Fallow Practices on Bacterial Community Structure in Paddy Fields.

Soil nutrients and microbial community play a central role in determining crop productivity in agroecosystems. However, the relationship between microbial community structure and soil nutrients in various crop rotation-fallow systems remains unclear. Thus, we designed a 3-year crop rotation-fallow field with five cropping systems (one continuous cropping, three rotational cropping, and one fallow system). We conducted a comprehensive analysis by evaluating crop yield, soil physicochemical properties, and overall bacteria composition. Our results showed that rotation-fallow treatments markedly influenced the crop yield and soil physicochemical properties. Proteobacteria, Acidobacteriota, and Chloroflexi were the dominant phyla in all rotation-fallow treatments. pH, available-phosphorus, total nitrogen, and soil organic matter had considerable effects on the soil bacterial community structure in 2019; however, only available-phosphorus had an impact on soil bacterial community in each treatment in 2020. In summary, with the increase of tillage years, different rotational fallow systems can increase paddy yield by promoting soil nutrient uptake and increasing the relative abundances of bacteria in paddy fields. IMPORTANCE Soil nutrients and microbial community play a central role in determining crop productivity. Therefore, elucidating the microbial mechanisms associated with different cropping systems is indispensable for understanding the sustainability of agroecosystem. In the present study, we designed a 3-year field rotation experiment using five cropping systems, including one continuous cropping, three rotational cropping, and one fallow system, to indagate the outcomes of soil microbial community structures in the different tillage systems. Our results showed that the different rotational fallow systems had positive impacts on crop yield, soil physicochemical properties, and bacterial community structure and that available phosphorus might be a key determinant for the limited bacterial community structure in various rotation-fallow systems following a 3-year field experiment. This study suggests that crop rotation-fallow systems play critical roles in improving bacterial community structure.