Transcriptome-based network analysis of cell cycle-related genes in response to blue and red light in maize.

In maize, blue and red light are key environmental factors regulating cell-cycle progression. We used transcriptomics to investigate and compare differential gene expression under the four light conditions: red light, blue light, red converted to blue and blue converted to red. A total of 23 differentially expressed genes were identified. The gene-gene interaction analysis indicated a significant interaction between four unidentified genes, 100191551, pco143873, 100284747 and pco060490, and cell-cycle-related genes. Using multiple sequence alignment analysis and protein structure comparisons, we show here that these four unidentified genes were characterized as ALP1-like, ALP1, cyclin P1-1 and AEBP2, respectively. By constructing a protein-protein interaction network, we inferred that 100191551 and pco143873 are potentially regulated to avoid DNA damage by abiotic stress response factors in the cell cycle. The gene 100284747 regulates the cell cycle in response to phosphate starvation signalling. The gene pco060490 potentially negatively regulates the cell cycle through the mediation of Histone H3 and CYCD6 in response to red light. In conclusion, the cell-cycle-related genes are sensitive to blue and red light, and four novel functional genes may be involved in the cell cycle.

Evaluation of Commercial Products for Colistin and Polymyxin B Susceptibility Testing for mcr-Positive and Negative Escherichia coli and Klebsiella pneumoniae in China.

Purpose: To evaluate the performance of five widespread commercial products for colistin and polymyxin B susceptibility testing in China for mcr-positive and -negative Escherichia coli and Klebsiella pneumoniae. Methods: A total of 132 E. coli and 83 K. pneumoniae strains (including 68 mcr-1-positive E. coli and 28 mcr-8-positive K. pneumoniae) were collected. We analysed the performance of colistin susceptibility (with Vitek 2 and Phoenix M50) and the performance of polymyxin B susceptibility (with DL-96II, MA120, and a Polymyxin B Susceptibility Test strip; POL E-strip). Broth microdilution was used as the gold standard. Categorical agreement (CA), essential agreement (EA), major error (ME), and very major error (VME) were calculated for comparisons. Results: For E. coli, the total CA, EA, ME, and VME to colistin were as follows: Vitek 2, 98.5%/98.5%/0%/2.9%; and Phoenix M50, 98.5%/97.7%/0%/2.9%. The total CA, EA, ME, and VME to polymyxin B were as follows: POL E-strip, 99.2%/63.6%/1.6%/0%; MA120, 70.0%/-/0%/58.8%; and DL-96II, 80.2%/-/1.6%/36.8%. Only Vitek 2 and Phoenix M50 presented satisfactory performances for mcr-1-positive E. coli. For K. pneumoniae, the total CA, EA, ME, and VME to colistin were as follows: Vitek 2, 73.2%/72.0%/0%/61.6%; and Phoenix M50, 74.7%/74.7%/0%/58.3%. The total CA, EA, ME, and VME to polymyxin B were as follows: POL E-strip, 91.6%/74.7%/2.1%/16.7%; MA120, 92.8%/-/2.1%/13.9%; and DL-96II, 92.2%/-/2.1%/8.3%. All systems were unsatisfactory for mcr-8-positive K. pneumoniae. When the susceptibility of mcr-negative strains was tested, all systems presented excellent performance. Conclusion: Vitek 2 and Phoenix M50 with colistin for E. coli showed acceptable performance regardless of mcr-1 expression, while DL-96II, MA120, and the POL E-strip performed worse for mcr-1-positive strains. Furthermore, mcr-8 greatly affected the performance of all systems with both colistin and polymyxin B for K. pneumoniae isolates.

Exogenous Melatonin Reprograms the Rhizosphere Microbial Community to Modulate the Responses of Barley to Drought Stress.

The rhizospheric melatonin application-induced drought tolerance has been illuminated in various plant species, while the roles of the rhizosphere microbial community in this process are still unclear. Here, the diversity and functions of the rhizosphere microbial community and related physiological parameters were tested in barley under the rhizospheric melatonin application and drought. Exogenous melatonin improved plant performance under drought via increasing the activities of non-structural carbohydrate metabolism enzymes and activating the antioxidant enzyme systems in barley roots under drought. The 16S/ITS rRNA gene sequencing revealed that drought and melatonin altered the compositions of the microbiome. Exogenous melatonin increased the relative abundance of the bacterial community in carbohydrate and carboxylate degradation, while decreasing the relative abundance in the pathways of fatty acid and lipid degradation and inorganic nutrient metabolism under drought. These results suggest that the effects of melatonin on rhizosphere microbes and nutrient condition need to be considered in its application for crop drought-resistant cultivation.

Postoperative Recovery Outcomes for Obese Patients Undergoing General Anesthesia: A Meta-Analysis of Randomized Controlled Trials.

Purpose: This study was performed to assess the postoperative recovery outcomes in obese patients undergoing general anesthesia. Methods: The eligible studies were identified from PubMed, EmBase, and the Cochrane library until December 2020. The standard mean differences (SMDs) with 95% confidence intervals (CIs) were used to calculate the role of desflurane, sevoflurane, and propofol on recovery outcomes, and the analyses using the random-effects model. Results: Eleven randomized controlled trials involving 713 obese patients undergoing general anesthesia were selected for final meta-analysis. We noted desflurane was associated with a shorter time to eye-opening than sevoflurane (SMD: -0.86; 95% CI, -1.43 to -0.28; P = 0.003). The use of desflurane with shorter time to extubation as compared with propofol (SMD: -1.13; 95% CI, -1.52 to -0.73; P < 0.001) or sevoflurane (SMD: -1.19; 95% CI, -2.15 to -0.22; P = 0.016), while sevoflurane was associated with longer time to extubation as compared with propofol (SMD: 1.47; 95% CI, 1.03 to 1.91; P < 0.001). Desflurane were associated with shorter time to stating name as compared with propofol (SMD: -1.40; 95% CI, -2.32 to -0.48; P = 0.003) or sevoflurane (SMD: -2.09; 95% CI, -3.33 to -0.85; P = 0.001). In addition, desflurane was associated with a longer time for orientation to place as compared with propofol (SMD: 0.65; 95% CI, 0.22 to 1.07; P = 0.003), while desflurane with shorter time for orientation to place as compared with sevoflurane (SMD: -0.88; 95% CI, -1.46 to -0.30; P = 0.003). Conclusions: The use of desflurane could provide better recovery outcomes in obese patients undergoing general anesthesia. Further large-scale trials should be comparison the long-term effectiveness of various anesthetics.

Parental drought priming enhances tolerance to low temperature in wheat (Triticum aestivum) offspring.

Low temperature is one of the major environmental stresses that limit crop growth and grain yield in wheat (Triticum aestivum L.). Drought priming at the vegetative stage could enhance wheat tolerance to later cold stress; however, the transgenerational effects of drought priming on wheat offspring's cold stress tolerance remains unclear. Here, the low temperature responses of offspring were tested after the parental drought priming treatment at grain filling stage. The offspring plants from parental drought priming treatment had a higher abscisic acid (ABA) level and lower osmotic potential (Ψo) than the control plants under cold conditions. Moreover, parental drought priming increased the antioxidant enzyme activities and decreased hydrogen peroxide (H2 O2 ) accumulation in offspring. In comparison to control plants, parental drought priming plants had a higher ATP concentration and higher activities of ATPase and the enzymes involved in sucrose biosynthesis and starch metabolism. The results indicated that parental drought priming induced low temperature tolerance in offspring by regulating endogenous ABA levels and maintaining the redox homeostasis and the balance of carbohydrate metabolism, which provided a potential approach for cold resistant cultivation in wheat.

Melatonin reduces nanoplastic uptake, translocation, and toxicity in wheat.

With increasing plastic production and consumption, large amounts of polystyrene nanoplastics are accumulated in soil due to improper disposal causing pollution and deleterious effects to environment. However, little information is available about how to alleviate the adverse impacts of nanoplastics on crops. In this study, the involvement of melatonin in modulating nanoplastic uptake, translocation, and toxicity in wheat plant was investigated. The results demonstrated that exogenous melatonin application reduced the nanoplastic uptake by roots and their translocation to shoots via regulating the expression of genes associated with aquaporin, including the upregulation of the TIP2-9, PIP2, PIP3, and PIP1.2 in leaves and TIP2-9, PIP1-5, PIP2, and PIP1.2 in roots. Melatonin activated the ROS scavenging system to maintain a better redox homeostasis and ameliorated the negative effects of nanoplastics on carbohydrate metabolism, hence ameliorated the plant growth and enhanced the tolerance to nanoplastics toxicity. This process was closely related to the exogenous melatonin application induced melatonin accumulation in leave. These results suggest that melatonin could alleviate the adverse effects of nanoplastics on wheat, and exogenous melatonin application might be used as a promising management strategy to sustain crop production in the nanoplastic-polluted soils.

Relationship between endophytic microbial diversity and grain quality in wheat exposed to multi-generational CO2 elevation.

To explore the potential association between the diversity of endophytic microorganisms and modifications of grain quality in wheat exposed to multi-generational elevated CO2 concentration, the grain quality attributes and microbial diversity were tested after five generations successively grown in ambient CO2 concentration (F5_A, 400 µmol L-1) and elevated CO2 concentration (F5_E, 800 µmol L-1). Elevated CO2 concentration significantly increased the grain number and starch concentration, while decreased the grain protein concentration. Multi-generational exposure to elevated CO2 concentration also led to significant changes in grain amino acid concentration. In response to the elevated CO2 concentration, Pseudomonas, Rhodococcus, Ralstonia, and Klebsiella were the dominant bacterial genera, while Penicillium, Cutaneotrichosporon, Fusarium, Sarocladium, Acremonium and Aspergillus were the dominant fungal genera in wheat grain. A significantly positive correlation was found between Pseudomonas, Penicillium and ratio of starch to protein concentration, implying that the multi-generational CO2 elevation induced modifications in grain quality might be associated with the changes in grain microbial diversity. The results of this study suggest that the endophytic microbes may play an important role in modulating the grain nutritional quality in wheat under multi-generational e[CO2] exposure, through regulating starch and N metabolism and production of secondary metabolites.

Abscisic acid-mimicking ligand AMF4 induced cold tolerance in wheat by altering the activities of key carbohydrate metabolism enzymes.

AMF4, a recently synthetic ABA-mimicking ligand, has been reported to have long-lasting effects in inducing the expression of stress-responsive genes, hence conferring abiotic tolerance in plants. To test the effect of AMF4 on cold tolerance induction, the wheat plants were firstly foliar sprayed with AMF4 (10 µM), then the AMF4 treated and the control plants were exposed to a 24-h low temperature treatment (2/0 °C). Under low temperature stress, the AMF plants possessed significantly higher relative water content, membrane stability index and ATP concentration in leaf, while lower leaf H2O2 concentration, compared with the control plants. The AMF4 treatment significantly increased the activities of APX, Ca2+-ATPase in the chloroplasts, while decreased SOD activity under low temperature, in relation to the control plants. In addition, the AMF plants showed significantly higher activities of key carbohydrate metabolism enzymes, such as UDP-glucose pyrophorylase, hexokinase, fructokinase, ADP-Glucose pyrophosphorylase, phosphoglucomutase, glucose-6-phosphate dehydrogenase and phosphoglucoisomerase, in relation to the control plants under low temperature. These results demonstrate that AMF4 could be used to induce cold tolerance in wheat, and provide novel insights into the potential ways to enhance abiotic stress tolerance using the synthetic ABA-mimicking ligands.

Nano-ZnO-Induced Drought Tolerance Is Associated with Melatonin Synthesis and Metabolism in Maize.

The applications of ZnO nanoparticles in agriculture have largely contributed to crop growth regulation, quality enhancement, and induction of stress tolerance, while the underlying mechanisms remain elusive. Herein, the involvement of melatonin synthesis and metabolism in the process of nano-ZnO induced drought tolerance was investigated in maize. Drought stress resulted in the changes of subcellular ultrastructure, the accumulation of malondialdehyde and osmolytes in leaf. The nano-ZnO (100 mg L-1) application promoted the melatonin synthesis and activated the antioxidant enzyme system, which alleviated drought-induced damage to mitochondria and chloroplast. These changes were associated with upregulation of the relative transcript abundance of Fe/Mn SOD, Cu/Zn SOD, APX, CAT, TDC, SNAT, COMT, and ASMT induced by nano-ZnO application. It was suggested that modifications in endogenous melatonin synthesis were involved in the nano-ZnO induced drought tolerance in maize.

Salt Priming Protects Photosynthetic Electron Transport against Low-Temperature-Induced Damage in Wheat.

Low temperature limits the photochemical efficiency of photosystems in wheat plants. To test the effect of salt priming on the photosynthetic electron transport in wheat under low temperature, the germinating seeds of a winter wheat cv. Jimai44 were primed with varying concentrations of NaCl solutions (0, 10, 30, and 50 mM NaCl, indicated by S0, S10, S30, and S50, respectively) for 6 d, and after 11 d of recovery, the seedlings were subsequently exposed to 24-h low-temperature stress (2 °C). Under low temperature, the S30 plants possessed the highest absorption flux per reaction center and higher density of reaction center per cross-section among the treatments. In addition, S30 plants had higher trapped energy flux for reducing QA and fraction of QA-reducing reaction centers and non-QB reducing center than the non-primed plants under low temperature, indicating that S30 plants could maintain the energy balance of photosystems and a relatively higher maximum quantum efficiency of photosystem II under low temperature. In addition, the low temperature-induced MDA accumulation and cell death were alleviated by salt priming in S30 plants. It was suggested that salt priming with an optimal concentration of NaCl solution (30 mM) during seed germination enhanced the photochemical efficiency of photosystems in wheat seedlings, which could be a potential approach to improve cold tolerance in wheat at an early stage.

Propofol Inhibits Proliferation, Migration, Invasion and Promotes Apoptosis Through Down-Regulating miR-374a in Hepatocarcinoma Cell Lines.

BACKGROUND: Propofol is a commonly used anaesthetic with controversial effects on cancer cells. We aimed to explore the functional roles of propofol in hepatocellular carcinoma (HCC) cells as well as the underlying mechanisms. METHODS: HepG2 and SMMC-7721 cells were used in this study. Firstly, the effects of propofol on cell viability, migration, invasion, apoptosis, and involved proteins were assessed by Cell Counting Kit-8 assay, Transwell assay, flow cytometry assay and Western blot analysis, respectively. Subsequently, alteration of miR-374a after stimulation of propofol was analyzed by qRT-PCR. miR-374a was overexpressed and the alteration of proteins in the Wnt/ß-catenin and PI3K/AKT pathways was detected by Western blot analysis. The downstream factor of miR-374a was finally studied. RESULTS: Propofol inhibited cell viability, migration and invasion but promoted apoptosis of HepG2 and SMMC-7721 cells. Meanwhile, cyclinD1, matrix metalloproteinase (MMP)-2 and MMP-9 were down-regulated while Bax/Bcl-2, cleaved caspase-3 and cleaved caspase-9 were up-regulated by propofol. Then, miR-374a level was reduced by propofol. Expression of Wnt3a, ß-catenin, p-PI3K and p-AKT was decreased by propofol, whereas these decreases were reversed by miR-374a overexpression. Finally, TP53 was proven to be target of miR-374a in HepG2 cells. CONCLUSION: Propofol inhibited cell proliferation, migration and invasion while promoted cell apoptosis of HepG2 and SMMC-7721 cells through inhibiting the Wnt/ß-catenin and PI3K/ AKT pathways via down-regulation of miR-374a. Besides, miR-374a affected propofol-treated HepG2 cells by targeting TP53.

Cold Tolerance of Photosynthetic Electron Transport System Is Enhanced in Wheat Plants Grown Under Elevated CO2.

The effects of CO2 elevation on sensitivity of photosynthetic electron transport system of wheat in relation to low temperature stress are unclear. The performance of photosynthetic electron transport system and antioxidant system in chloroplasts was investigated in a temperature sensitive wheat cultivar Lianmai6 grown under the combination of low temperature (2 days at 2/-1°C in the day/night) and CO2 elevation (800 µmol l-1). It was found that CO2 elevation increased the efficiency of photosynthetic electron transport in wheat exposed to low temperature stress, which was related to the enhanced maximum quantum yield for electron transport beyond QA and the increased quantum yield for reduction of end electron acceptors at the PSI acceptor side in plants under elevated CO2. Also, under low temperature, the activities of ATPases, ascorbate peroxidase, and catalase in chloroplasts were enhanced in wheat under elevated CO2. It suggested that the cold tolerance of photosynthetic electron transport system is enhanced by CO2 elevation.

Cold Priming Induced Tolerance to Subsequent Low Temperature Stress is Enhanced by Melatonin Application during Recovery in Wheat.

Cold priming can alleviate the effects of subsequent cold stress on wheat plant growth. Melatonin plays a key role in cold stress response in plants. In this study, the effects of foliar melatonin application during recovery on the cold tolerance of cold primed wheat plants were investigated. It was found that both melatonin and cold priming increased the photosynthetic rate and stomatal conductance, enhanced the activities of antioxidant enzymes, and altered the related gene expressions in wheat under cold stress. Melatonin application is helpful for the photosynthetic carbon assimilation and membrane stability of the cold primed plants under cold stress. These results suggested that foliar melatonin application during recovery enhanced the cold priming induced tolerance to subsequent low temperature stress in wheat.

Blood transfusion and risk of atrial fibrillation after coronary artery bypass graft surgery: A meta-analysis of cohort studies.

The aim of this study was to systematically evaluate the effect of blood transfusion (BT) on postoperative atrial fibrillation (AF) in adult patients who had undergone coronary artery bypass grafting (CABG) surgery.PubMed, Embase, and Cochrane Library databases from inception to January 2017 were searched. Cohort studies were searched that evaluated the association between BT and the risk of postoperative AF in adult patients who had undergone CABG surgery. Study quality was assessed by using the Newcastle-Ottawa scale (NOS). A meta-analysis was performed with the random-effect model.Eight cohort studies involving 7401 AF cases and 31,069 participants were identified and included in our data analysis. The pooled odds ratio of postoperative AF in patients with BT was 1.45 (95% confidence interval, 1.26-1.67), with significant heterogeneity (P < .0001, I = 79%). Excluding one study that had an off-pump CABG did not significantly impact this result (odds ratio, 1.36; 95% confidence interval, 1.23-1.50; n = 7). To examine the stability of the primary results, we performed subgroup analyses. The association between BT and the risk of postoperative AF was similar, as determined in the stratified analyses conducted according to study design, type of surgery, and country.The findings of the present meta-analysis demonstrated a statistically significant increase in postoperative AF risk among adult patients with BT. Further prospective large-scale studies are needed to establish causality and to elucidate the underlying mechanisms.

Enriched housing promotes post-stroke neurogenesis through calpain 1-STAT3/HIF-1α/VEGF signaling.

Enriched environment (EE) has been shown to promote neurogenesis and functional recovery after ischemic stroke. However, the underlying molecular mechanisms are not fully understood. In this study, C57BL/6 mice underwent middle cerebral artery occlusion (60 min) followed by reperfusion, after which mice were housed in either standard environment (SE) or EE and allowed to survive for 3, 4, 6 or 10 weeks. Ipsilateral subventricular zone (SVZ) or striatum cells were dissociated from ischemic hemispheric brains of enriched mice at 14 days post-ischemia (dpi) and cultured in vitro. Our data showed that post-ischemic EE inhibited calpain 1 activity, and increased the expression of phosphorylated signal transducer and activator of transcription 3 (p-STAT3) in the ischemic hemisphere of enriched mice at 21 dpi. Calpain 1-specific inhibitor PD151746 further increased p-STAT3 expression and augmented the promoting effects of EE on post-stroke SVZ neural precursor cells (NPCs) proliferation and functional recovery. EE also increased the expression of hypoxia-inducible factor 1-alpha (HIF-1α) and vascular endothelial growth factor (VEGF) in the ischemic hemisphere at 21 dpi. Inhibition of the JAK/STAT3 pathway with AG490 decreased the expression of HIF-1α and VEGF. Furthermore, inhibition of HIF-1α with 2-methoxyestradiol robustly abolished EE-induced elevation of VEGF l expression. Furthermore, VEGF-A promoted the production and secretion of high mobility group box-1 protein (HMGB1) from reactive astrocytes in vitro. Culture supernatant from reactive astrocytes treated with VEGF-A promoted the proliferation and differentiation of NPCs. Glycyrrhizin reversed the promoting effects of EE on post-stroke neurorepair and functional recovery in vivo. Taken together, our data indicate that EE promotes post-stroke functional recovery through the inhibition of calpain 1 activity, and subsequent STAT3-HIF-1α-VEGF-mediated neurogenesis.

Melatonin alleviates low PS I-limited carbon assimilation under elevated CO2 and enhances the cold tolerance of offspring in chlorophyll b-deficient mutant wheat.

Melatonin is involved in the regulation of carbohydrate metabolism and induction of cold tolerance in plants. The objective of this study was to investigate the roles of melatonin in modulation of carbon assimilation of wild-type wheat and the Chl b-deficient mutant ANK32B in response to elevated CO2 concentration ([CO2 ]) and the transgenerational effects of application of exogenous melatonin (hereafter identified as melatonin priming) on the cold tolerance in offspring. The results showed that the melatonin priming enhanced the carbon assimilation in ANK32B under elevated [CO2 ], via boosting the activities of ATPase and sucrose synthesis and maintaining a relatively higher level of total chlorophyll concentration in leaves. In addition, melatonin priming in maternal plants at grain filling promoted the seed germination in offspring by accelerating the starch degradation and improved the cold tolerance of seedlings through activating the antioxidant enzymes and enhancing the photosynthetic electron transport efficiency. These findings suggest the important roles of melatonin in plant response to future climate change, indicating that the melatonin priming at grain filling in maternal plants could be an effective approach to improve cold tolerance of wheat offspring at seedling stage.

Melatonin Improves the Photosynthetic Carbon Assimilation and Antioxidant Capacity in Wheat Exposed to Nano-ZnO Stress.

The release of nanoparticles into the environment is inevitable, which has raised global environmental concern. Melatonin is involved in various stress responses in plants. The present study investigated the effects of melatonin on photosynthetic carbon (C) assimilation and plant growth in nano-ZnO stressed plants. It was found that melatonin improved the photosynthetic C assimilation in nano-ZnO stressed wheat plants, mainly due to the enhanced photosynthetic energy transport efficiency, higher chlorophyll concentration and higher activities of Rubisco and ATPases. In addition, melatonin enhanced the activities of antioxidant enzymes to protect the photosynthetic electron transport system in wheat leaves against the oxidative burst caused by nano-ZnO stress. These results suggest that melatonin could improve the tolerance of wheat plants to nano-ZnO stress.

Monitoring of Gas Emboli During Hysteroscopic Surgery: A Prospective Study.

OBJECTIVES: Previous studies have demonstrated a high frequency of gas emboli during hysteroscopy, but guidelines for the prevention, early detection, and intervention of gas embolism during hysteroscopic procedures are still lacking. This study aimed to gain a clearer understanding of risk factors and specific signs and symptoms associated with gas emboli. METHODS: This prospective study enrolled 120 women scheduled for hysteroscopy using 5% glucose as distension medium. The gas bubbles were monitored sequentially in internal iliac vein, common iliac vein, inferior vena cava, superior vena cava, heart, and pulmonary artery under the gray-scale imaging of Doppler ultrasound. The frequency, extent, and the hemodynamic and respiratory effects of gas emboli were evaluated. The interventions and outcomes were recorded. The risk factors associated with gas emboli, and their relationship with the frequency and extent of gas emboli, were assessed. RESULTS: In our study, evidence of gas emboli under Doppler ultrasound monitoring was observed in 44 (36.7%) patients. The operation was continued and finished as soon as possible for patients presenting with stable vital signs or transient hemodynamic and respiratory changes, which resolved spontaneously without intervention. The operation was paused for patients presenting with significant hemodynamic changes or loss of consciousness, and the operation was resumed shortly after resumption of stable vital signs following symptomatic treatment. All patients in our study finished the operation and recovered without developing serious complications. Data analysis showed prolonged procedure duration and increased bleeding volume were both positively correlated with the frequency and extent of gas emboli. CONCLUSION: Our study demonstrated a high frequency of gas emboli during hysteroscopy. Doppler ultrasonic monitoring combined with a clearer understanding of specific signs, symptoms, and risk factors will facilitate early detection and intervention of gas emboli during hysteroscopy.

Arbuscular mycorrhiza improve growth, nitrogen uptake, and nitrogen use efficiency in wheat grown under elevated CO2.

Effects of the arbuscular mycorrhizal (AM) fungus Rhizophagus irregularis on plant growth, carbon (C) and nitrogen (N) accumulation, and partitioning was investigated in Triticum aestivum L. plants grown under elevated CO2 in a pot experiment. Wheat plants inoculated or not inoculated with the AM fungus were grown in two glasshouse cells with different CO2 concentrations (400 and 700 ppm) for 10 weeks. A (15)N isotope labeling technique was used to trace plant N uptake. Results showed that elevated CO2 increased AM fungal colonization. Under CO2 elevation, AM plants had higher C concentration and higher plant biomass than the non-AM plants. CO2 elevation did not affect C and N partitioning in plant organs, while AM symbiosis increased C and N allocation into the roots. In addition, plant C and N accumulation, (15)N recovery rate, and N use efficiency (NUE) were significantly higher in AM plants than in non-AM controls under CO2 enrichment. It is concluded that AM symbiosis favors C and N partitioning in roots, increases C accumulation and N uptake, and leads to greater NUE in wheat plants grown at elevated CO2.

Effect of different arbuscular mycorrhizal fungi on growth and physiology of maize at ambient and low temperature regimes.

The effect of four different arbuscular mycorrhizal fungi (AMF) on the growth and lipid peroxidation, soluble sugar, proline contents, and antioxidant enzymes activities of Zea mays L. was studied in pot culture subjected to two temperature regimes. Maize plants were grown in pots filled with a mixture of sandy and black soil for 5 weeks, and then half of the plants were exposed to low temperature for 1 week while the rest of the plants were grown under ambient temperature and severed as control. Different AMF resulted in different root colonization and low temperature significantly decreased AM colonization. Low temperature remarkably decreased plant height and total dry weight but increased root dry weight and root-shoot ratio. The AM plants had higher proline content compared with the non-AM plants. The maize plants inoculated with Glomus etunicatum and G. intraradices had higher malondialdehyde and soluble sugar contents under low temperature condition. The activities of catalase (CAT) and peroxidase of AM inoculated maize were higher than those of non-AM ones. Low temperature noticeably decreased the activities of CAT. The results suggest that low temperature adversely affects maize physiology and AM symbiosis can improve maize seedlings tolerance to low temperature stress.