Prognostic value and immunological roles of GPX3 in gastric cancer.

Objective: The prognosis for gastric cancer (GC), a prevalent tumor of the digestive system, is unfavorable. The involvement of glutathione peroxidase 3 (GPX3) in tumorigenesis is significant, yet its specific role in GC remains insufficiently investigated. Thus, the aim of this study was to determine the potential impact of GPX3 on GC and elucidate the underlying mechanism. Methods: The expression and survival of GPX3 in GC were analyzed using TCGA data. Additionally, the GPX3 mRNA and protein levels in GC were also assessed using datasets from GTEx, GEPIA, and HPA. A total of 38 pairs of GC tissues, along with their adjacent normal tissues, were collected from the Tianjin Medical University General Hospital, accompanied by detailed clinical information. The expression levels of GPX3 were subsequently determined for the purpose of validation. Following expression, correlation, and survival analyses, we proceeded to investigate the upstream non-coding RNA (ncRNA) of GPX3 using starBase and miRNet. Additionally, the co-expression networks of GPX3 were examined based on LinkedOmics. Lastly, we explored the correlation between GPX3 and immune cell infiltration, as well as the biomarkers of immune cells and immune checkpoints in GC. Furthermore, the GDSC database offered valuable drug sensitivity information. Results: A lower expression of GPX3 was observed in individuals with GC, while a higher expression of GPX3 was associated with a poorer prognosis. The DUBR/hsa-miR-502-3p/GPX3 pathway was identified as the most promising upstream ncRNA pathway related to GPX3 in GC. GO and KEGG enrichment analysis revealed that GPX3 expression was linked to coagulation cascades and cell locomotion. Furthermore, GPX3 levels in GC were positively correlated with immune cell infiltration, immune cell biomarkers, and immune checkpoint expression. The group with low GPX3 expression also exhibited increased sensitivity to 5-fluorouracil, doxorubicin, and other drugs. Conclusions: Collectively, we hypothesized that the potential involvement of non-coding RNAs in the downregulation of GPX3 could contribute to the inhibition of tumor formation during the malignant transition from gastritis to GC. Nevertheless, it was plausible that GPX3 may also facilitate tumor progression to advanced stages by promoting immune cell infiltration and activating immune checkpoints.

Vertical distribution of gas exchanges and their integration throughout the entire canopy in a maize field.

Fluxes of carbon and water along a vertical profile within a canopy, particularly the associations between canopy and ecosystem levels, are not well studied. In this study, gas exchange along the vertical profile in a maize canopy was examined. The relationships between leaf- and ecosystem-level carbon and water fluxes were compared. The results from research conducted over two growing seasons showed that during vegetative growth, the top and middle leaf layers in the canopy contribute most to the carbon and water fluxes of the entire canopy. During the grain-filling stage, gas exchange processes were performed mostly in the middle leaves with and near the ears. Significant relationships were observed between the net ecosystem CO2 exchange rate (NEE) plus soil respiration and the assumed canopy levels (Acanopy) and between evapotranspiration rates at the ecosystem (ET) and assumed canopy levels (Ecanopy). This highlights the close associations between these parameters by integrating the leaf gas exchange rates measured in a conventional leaf cuvette and those at the ecosystem level via the eddy covariance technique. These results improve our understanding of how carbon assimilation varies vertically within a canopy, highlighting the critical role of ear leaves.

Photosynthetic resistance and resilience under drought, flooding and rewatering in maize plants.

Abnormally altered precipitation patterns induced by climate change have profound global effects on crop production. However, the plant functional responses to various precipitation regimes remain unclear. Here, greenhouse and field experiments were conducted to determine how maize plant functional traits respond to drought, flooding and rewatering. Drought and flooding hampered photosynthetic capacity, particularly when severe and/or prolonged. Most photosynthetic traits recovered after rewatering, with few compensatory responses. Rewatering often elicited high photosynthetic resilience in plants exposed to severe drought at the end of plant development, with the response strongly depending on the drought severity/duration. The associations of chlorophyll concentrations with photosynthetically functional activities were stronger during post-tasseling than pre-tasseling, implying an involvement of leaf age/senescence in responses to episodic drought and subsequent rewatering. Coordinated changes in chlorophyll content, gas exchange, fluorescence parameters (PSII quantum efficiency and photochemical/non-photochemical radiative energy dissipation) possibly contributed to the enhanced drought resistance and resilience and suggested a possible regulative trade-off. These findings provide fundamental insights into how plants regulate their functional traits to deal with sporadic alterations in precipitation. Breeding and management of plants with high resistance and resilience traits could help crop production under future climate change.

Responses of plant biomass and yield component in rice, wheat, and maize to climatic warming: a meta-analysis.

MAIN CONCLUSION: Responses of plant biomass and yield components to warming are species-specific and are shifted as increased warming magnitude rises; this finding improves the results of IPCC AR5. The responses of crop yields to climatic warming have been extensively reported from experimental results, historical yield collections, and modeling research. However, an integrative report on the responses of plant biomass and yield components of three major crops to experimental warming is lacking. Here, a meta-analysis based on the most recent warming experiments was conducted to quantify the climatic warming responses of the biomass, grain yield (GY), and yield components of three staple crops. The results showed that the wheat total aboveground biomass (TAGB) increased by 6.0% with general warming, while the wheat GY did not significantly respond to warming; however, the responses shifted with increases in the mean growing season temperature (MGST). Negative effects on wheat TAGB and GY appeared when the MGSTs were above 15 °C and 13 °C, respectively. The wheat GY and the number of grains per panicle decreased by 8.4% and 7.5%, respectively, per degree Celsius increase. Increases in temperature significantly reduced the rice TAGB and GY by 4.3% and 16.6%, respectively, but rice straw biomass increased with increasing temperature. However, the rice grain weight and the number of panicles decreased with continuous increasing temperature (ΔTa). The maize biomass, GY, and yield components all generally decreased with climatic warming. Finally, the crop responses to climatic warming were significantly influenced by warming time, warming treatment facility, and methods. Our findings can improve the assessment of crop responses to climatic warming and are useful for ensuring food security while combating future global climate change.

Efficacy and safety of endoscopic submucosal dissection for gastrointestinal neuroendocrine tumors: a 10-year data analysis of Northern China.

Objective: Endoscopy is the main method to treat gastrointestinal neuroendocrine tumors (GI-NETs), but the specific indications are still controversial. We aim to investigate the clinical outcomes of GI-NETs patients who experienced endoscopic submucosal dissection (ESD). Methods: We retrospectively reviewed the clinical features and prognosis of 65 GI-NETs patients who underwent ESD between 2008 and 2018. Results: A total of 65 patients diagnosed with GI-NETs pathologically, bearing 75 lesions, were found by endoscopy incidentally for other symptoms. The locations of these lesions were stomach (n = 24), duodenal bulb (n = 4) and rectum (n = 47). The diameter of 75 tumors were as follows: size ≤ 1 cm (78.7%), 1 cm < size ≤ 2 cm (17.3%), 2 cm < size ≤ 3.5 cm (4.0%). Endoscopic ultrasonography (EUS) suggested that 72 lesions were confined to submucosa and 3 lesions invaded into muscularis propria. The rates of en bloc resection and complete resection were all 100% and the rates of intraoperative bleeding and perforation were 2.7% and 1.3%, respectively. None of the 65 patients had lymph nodes and distant metastasis during the period of study. Conclusion: For GI-NETs without lymph nodes and distant metastases, the lesion confined to submucosa with the diameter ≤1 cm is absolute indication of ESD. For rectal neuroendocrine tumors limited in submucosa with the diameter between 1 and 2 cm, and Type 1 gastric neuroendocrine tumors predicted to be T2, ESD should be prioritized to preserve gastrointestinal volume and function at initial treatment.

[Impact of deep slow-wave sleep deprivation on oxidative stress response of the testis tissue in rats].

OBJECTIVE: To investigate the influence of deep slow-wave sleep deprivation on the oxidative stress of testicular tissue in rats. METHODS: Thirty-six 5-week-old male Wistar rats were equally randomized into deep slow-wave sleep deprivation group (SD1), deep slow-wave sleep and duration sleep deprivation group ( SD2), and a cage control group (CC). The rat model of deep slow-wave sleep deprivation was established using the flowerpot technique. The rats in the SD1 group were interfered every 24 minutes and deprived of 12 hours of sleep at night, those in the SD2 group deprived of 8 minutes of sleep at an interval of 24 minutes and 12 hours of sleep at night, and those in the CC group exposed to 12 hours of daylight and 12 hours of darkness. After 28 days, all the rats were executed for measurement of the testis volume and protein content, determination of the methane dicarboxylic aldehyde (MDA) level and activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px), and observation of the pathological changes in the testicular tissue under the microscope. RESULTS: Compared with the CC group, the rats in the SD1 and SD2 groups showed significantly reduced body weight (ï¼»268.5 ± 1.6ï¼½ vs ï¼»248.1 ± 25.1ï¼½andï¼»232.9 ± 10.1ï¼½g, P<0.05) and increased relative testis mass (ï¼»50.0 ± 1.3ï¼½ vs ï¼»57.9 ± 6.1ï¼½ and ï¼»54.9 ± 3.5ï¼½ ×10⁻², P<0.05). Statistically significant differences were found between the CC and SD2 groups in the contents of protein (ï¼»6.3 ± 1.4ï¼½ vs ï¼»4.5 ± 0.9ï¼½ gpro/L, P<0.05) and MDA (ï¼»1.1 ± 0.1ï¼½ vs ï¼»1.3 ± 0.3ï¼½ nmol/mgpro, P<0.05) and the activities of SOD (ï¼»104.3 ± 33.1ï¼½ vs ï¼»135.2 ± 26.9ï¼½ U/mgpro, P<0.05) and GSH-Px (ï¼»15.6 ± 4.0ï¼½ vs ï¼»21.7 ± 4.3ï¼½ U/mgpro, P<0.05), but not between the CC and SD1 groups (P>0.05). The lumens in the testis were narrowed, with obvious hyperplasia, hyperemia and edema in the peripheral interstitial tissue, but no significant pathologic changes were observed in the testis tissue of the SD1 group. CONCLUSIONS: Long-term deprivation of deep slow-wave sleep impairs the structure of the testis tissue and induces oxidative stress response in rats.

Phenological characteristics of net ecosystem carbon exchange of Stipa krylovii steppe in Inner Mongolia, China and its remote sensing monitoring.

To accurately monitor the phenology of net ecosystem carbon exchange (NEE) in grasslands with remote sensing, we analyzed the variations in NEE and its phenology in the Stipa krylovii steppe and discussed the remote sensing vegetation index thresholds for NEE phenology, with the observational data from the Inner Mongolia Xilinhot National Climate Observatory's eddy covariance system and meteorological gradient observation system during 2018-2021, as well as Sentinel-2 satellite data from January 1, 2018 to December 31, 2021. Results showed that, from 2018 to 2021, NEE exhibited seasonal variations, with carbon sequestration occurring from April to October and carbon emission in other months, resulting in an overall carbon sink. The average Julian days for the start date (SCUP) and the end date (ECUP) of carbon uptake period were the 95th and 259th days, respectively, with an average carbon uptake period lasting 165 days. Photosynthetically active radiation showed a negative correlation with daily NEE, contributing to carbon absorption of grasslands. The optimal threshold for capturing SCUP was a 10% threshold of the red-edge chlorophyll index, while the normalized difference vegetation index effectively reflected ECUP with a threshold of 75%. These findings would provide a basis for remote sensing monitoring of grassland carbon source-sink dynamics.

Dynamic monitoring of maize grain quality based on remote sensing data.

Remote sensing data have been widely used to monitor crop development, grain yield, and quality, while precise monitoring of quality traits, especially grain starch and oil contents considering meteorological elements, still needs to be improved. In this study, the field experiment with different sowing time, i.e., 8 June, 18 June, 28 June, and 8 July, was conducted in 2018-2020. The scalable annual and inter-annual quality prediction model for summer maize in different growth periods was established using hierarchical linear modeling (HLM), which combined hyperspectral and meteorological data. Compared with the multiple linear regression (MLR) using vegetation indices (VIs), the prediction accuracy of HLM was obviously improved with the highest R 2, root mean square error (RMSE), and mean absolute error (MAE) values of 0.90, 0.10, and 0.08, respectively (grain starch content (GSC)); 0.87, 0.10, and 0.08, respectively (grain protein content (GPC)); and 0.74, 0.13, and 0.10, respectively (grain oil content (GOC)). In addition, the combination of the tasseling, grain-filling, and maturity stages further improved the predictive power for GSC (R 2 = 0.96). The combination of the grain-filling and maturity stages further improved the predictive power for GPC (R 2 = 0.90). The prediction accuracy developed in the combination of the jointing and tasseling stages for GOC (R 2 = 0.85). The results also showed that meteorological factors, especially precipitation, had a great influence on grain quality monitoring. Our study provided a new idea for crop quality monitoring by remote sensing.

Roles and action mechanisms of bile acid-induced gastric intestinal metaplasia: a review.

Gastric intestinal metaplasia (IM) is a precancerous lesion that increases the risk of subsequent gastric cancer (GC) development. Therefore, the mechanism of IM has been the focus of basic and clinical research. Helicobacter pylori (H. pylori) infection has been recognized as the main pathogenesis of gastric IM. However, more and more studies have shown that chronic inflammation of gastric mucosa caused by bile reflux is the key pathogenic factor of gastric IM. Bile reflux activates the expression of IM biomarkers via the bile acid receptor. In addition, microRNAs, exosomes, and epigenetics are also involved in the occurrence and development of bile acid-induced gastric IM. Currently, the relevant research is still very few. The molecular mechanism of the phenotypic transformation of gastrointestinal epithelial cells induced by bile acids has not been fully understood. This article mainly reviews the physiology and pathology of bile acid, mechanism of gastric IM induced by bile acid, bile acid receptors, and so on, in order to provide reference for further research.

Development and validation of a nomogram based on neutrophil-to-lymphocyte ratio and fibrinogen-to-lymphocyte ratio for predicting recurrence of colorectal adenoma.

Background: There are many risk factors for the recurrence of colorectal adenoma (CRA). The purpose of this study was to explore the predictive performance of fibrinogen-to-lymphocyte ratio (FLR) and neutrophil-to-lymphocyte ratio (NLR) on the recurrence of CRA and to construct a predictive model. Methods: This study analyzed the clinicopathological features of 421 CRA patients who underwent colonoscopy and adenectomy, and evaluated the recurrence of polyps under colonoscopy. Among them, 301 were training cohort and 120 were validation cohort. Multivariate logistic regression was used to identify independent risk factors associated with CRA recurrence. Established a nomogram model to predict the risk of recurrence in CRA patients using independent risk factors. The receiver operating characteristic (ROC) curves were used to verify the nomogram model discrimination. Calibration curves were used to verify the model calibration degree. The decision curve analysis (DCA) curves were used to verify the clinical efficacy of the nomogram model. Results: Totally, six independent predictors, including smoking, diabetes, adenoma number, adenoma size, NLR, and FLR, were enrolled in the nomogram. In the training cohort and validation cohort, the area under the curve (AUC) of the nomogram for predicting the risk of CRA recurrence was 0.846 and 0.841, respectively. The calibration curves displayed a good agreement. DCA curves showed that this model had a high net clinical benefit. Conclusions: Smoking, diabetes, adenoma number, adenoma size, NLR, and FLR were influencing factors for CRA recurrence.

Rebamipide attenuates alcohol-induced gastric epithelial cell injury by inhibiting endoplasmic reticulum stress and activating autophagy-related proteins.

Apoptosis of gastric mucosa epithelial cells caused by the abuse of alcohol produces injury to the gastric mucosa and acute or chronic gastritis. In recent years, it has been demonstrated that endoplasmic reticulum stress (ERS) is involved in mediating apoptosis, and that autophagy has a protective effect on survival of cells. Rebamipide is a gastric mucosal protectant used to treat gastritis and stomach ulcers. In this study, ethanol was used to overstimulate gastric mucosal epithelial cells and gavage mice. It was found that 400 mmol/L ethanol overstimulation could activate ERS and induce apoptosis (control vs ethanol treatment: 15.24 ± 1.10% vs 33.80 ± 1.47%, P < 0.001); but could not activate the autophagy pathway. Rebamipide intervention can reduce apoptosis rate (20.78 ± 1.63%), and significantly inhibit the activation of ERS and the active ERS-related downstream NF-κB signaling pathway. Additionally, rebamipide can activate the expression of autophagy-related pathway proteins and increase the expression of p-ERK and p-p38. In addition, rebamipide relieved oxidative stress after an ethanol insult. In the present study, molecular evidence of rebamipide inhibition of ERS and regulation of the protein expression of autophagy pathway components were produced using an acute alcoholic gastric mucosal injury model. This model provides a new approach for investigating the effects of rebamipide treatment on alcohol-induced gastric mucosal damage.

A novel robust nomogram based on preoperative hemoglobin and albumin levels and lymphocyte and platelet counts (HALP) for predicting lymph node metastasis of gastric cancer.

BACKGROUND: Accurate assessment of lymph node status in gastric cancer (GC) patients can help to select appropriate treatment strategies for GC, but the diagnostic accuracy of conventional methods needs to be improved. The aim of this study was to investigate the predictive value of preoperative hemoglobin and albumin levels and lymphocyte and platelet counts (HALP) on lymph node status in GC patients and to construct a risk prediction model. METHODS: This study retrospectively analyzed the clinicopathological characteristics of 349 patients with GC who underwent radical gastrectomy, among which 250 patients were recruited in the training cohort and 99 patients in the independent validation cohort. Significant risk factors in univariate analysis were further identified as independent variables in multivariate logistic regression analysis, which were then incorporated and presented in a nomogram. Receiver operating characteristic (ROC) curves, Calibration curve and decision curve analysis (DCA) curves were used to evaluate the discrimination, prediction accuracy and clinical effectiveness of the model. RESULTS: Multifactorial logistic regression analysis showed that alcohol use (OR =2.203, P=0.036), Depth of invasion (OR =7.756, P<0.001), differentiation (OR =2.252, P=0.018), carcinoembryonic antigen (CEA) (OR =2.443, P=0.017), carbohydrate antigen 19-9 (CA199) (OR =2.715, P=0.008) and HALP (OR =2.276, P=0.032) were independent risk factors for lymph node metastasis (LNM) in GC. We used these factors to construct a nomogram for predicting LNM in GC patients, and the ROC curves showed good discrimination of the model with AUC values of 0.854 (training cohort) and 0.868 (validation cohort), respectively, and the calibration curves showed good predictive ability of the nomogram, in addition to the DCA curves results showed the clinical usefulness of the model. CONCLUSIONS: In conclusion, we established a nomogram for predicting LNM in patients with GC.

Lactic Acid-Producing Probiotic Saccharomyces cerevisiae Attenuates Ulcerative Colitis via Suppressing Macrophage Pyroptosis and Modulating Gut Microbiota.

Lactic acid, a metabolic by-product of host and intestinal microbiota, has been recovered as an active signal molecule in the immune system. In this study, a lactic acid biosynthesis pathway that directly produces lactic acid from glucose rather than ethanol with high production was reconstructed in Saccharomyces cerevisiae. The engineered S. cerevisiae showed anti-inflammatory activity in dextran sulfate sodium (DSS)-induced mice with improved histological damage, increased mucosal barrier, and decreased intestinal immune response. Lactic acid regulated the macrophage polarization state and inhibited the expression of pro-inflammatory cytokines in vivo and in vitro. Increasing the macrophage monocarboxylic acid transporter-mediated active lactic acid uptake suppressed the excessive activation of the NLRP3 inflammasome and the downstream caspase-1 pathway in macrophages. Moreover, lactic acid promoted histone H3K9 acetylation and histone H3K18 lactylation. Meanwhile, the engineered S. cerevisiae altered the diversity and composition of the intestinal microbiota and changed the abundance of metabolic products in mice with colitis. In conclusion, this study shows that the application of engineered S. cerevisiae attenuated DSS-induced colitis in mice via suppressing macrophage pyroptosis and modulating the intestinal microbiota, which is an effective and safe treatment strategy for ulcerative colitis.

Role of the Aryl Hydrocarbon Receptor and Gut Microbiota-Derived Metabolites Indole-3-Acetic Acid in Sulforaphane Alleviates Hepatic Steatosis in Mice.

Scope: Gut microbiome-derived metabolites are the major mediators of diet-induced host-microbial interactions. Aryl hydrocarbon receptor (AHR) plays a crucial role in glucose, lipid, and cholesterol metabolism in the liver. In this study, we aimed to investigate the role of indole-3-acetic acid (IAA) and AHR in sulforaphane (SFN) alleviates hepatic steatosis in mice fed on a high-fat diet (HFD). Methods and Results: The HFD-fed male C57BL/6 mice were intervened with SFN for 6 weeks. HFD-mice showed classical pathophysiological characteristics of hepatic steatosis. The results showed that SFN significantly reduced body weight, liver inflammation and hepatic steatosis in HFD-fed mice. SFN reduced hepatic lipogenesis by activating AHR/SREBP-1C pathway, which was confirmed in HepG2 cell experiments. Moreover, SFN increased hepatic antioxidant activity by modulating Nrf-2/NQO1 expression. SFN increased serum and liver IAA level in HFD mice. Notably, SFN manipulated the gut microbiota, resulting in reducing Deferribacteres and proportions of the phylum Firmicutes/Bacteroidetes and increasing the abundance of specific bacteria that produce IAA. Furthermore, SFN upregulated Ahr expression and decreased the expression of inflammatory cytokines in Raw264.7 cells. Conclusions: SFN ameliorated hepatic steatosis not only by modulating lipid metabolism via AHR/SREBP-1C pathway but regulating IAA and gut microbiota in HFD-induced NAFLD mice.

Improving smallholder farmers' maize yields and economic benefits under sustainable crop intensification in the North China Plain.

To meet the food demands of a growing population, the maize production systems deployed by smallholders in China have tended towards extremely intensive planting and excessive use of fertilizers, which have caused serious environmental impacts. This study investigated the balance between the maize yield and nitrogen (N) input in the North China Plain (NCP), which is one of the most important grain-producing region in China. Our study compared yield simulations generated by the DSSAT-CERES-Maize model with actual data from a number of multi-site field experiments and an extensive household surveys encompassing 1671 farmers. The smallholders' maize cultivars, plant population, and amount of N input on the crop yield and how these affects the economic benefits were analyzed. The results showed that the average traditional farming methods' yield was 72% of the attainable yield, which means that farmers have ample room to improve their yields. We also found that the maize yields varied widely between farmers, and that most of them applied excessive amounts of N but failing to achieve an optimal yield due to poor fertilization management techniques. The study found that the economic benefits achieved by the farmers were low, but after deploying high-yield (HY) methods, the yield was increased by 34.9% and the economic benefits by 14.4%. The greenhouse gas (GHG) emissions associated with the traditional farming methods were high and could potentially be reduced by 48.6%. All in all, farmers should be given guidance on how to appropriately increase the plant population, reduce the input of N fertilizer, and optimize farmland management measures, so that China can achieve intensive but sustainable agricultural production at a lower environmental cost. It was concluded that there are still numerous biological and abiotic factors that restrict production increases by smallholders. These factors vary from region to region and require further investigation.

Contrasting responses of steppe Stipa ssp. to warming and precipitation variability.

Climate change, characterized by warming and precipitation variability, restricted the growth of plants in arid and semiarid areas, and various functional traits are impacted differently. Comparing responses of functional traits to warming and precipitation variability and determining critical water threshold of dominate steppe grasses from Inner Mongolia facilitates the identification and monitoring of water stress effects. A combination of warming (ambient temperature, +1.5°C and +2.0°C) and varying precipitation (-30%, -15%, ambient, +15%, and +30%) manipulation experiments were performed on four Stipa species (S. baicalensis, S. bungeana, S. grandis, and S. breviflora) from Inner Mongolia steppe. The results showed that the functional traits of the four grasses differed in their responses to precipitation, but they shared common sensitive traits (root/shoot ratio, R/S, and specific leaf area; SLA) under ambient temperature condition. Warming increased the response of the four grasses to changing precipitation, and these differences in functional traits resulted in changes to their total biomass, with leaf area, SLA, and R/S making the largest contributions. Critical water thresholds of the four grasses were identified, and warming led to their higher optimum precipitation requirements. The four steppe grasses were able to adapt better to mild drought (summer precipitation decreased by 12%-28%) when warming 1.5°C rather than 2.0°C. These results indicated that if the Paris Agreement to limit global warming to 1.5°C will be accomplished, this will increase the probability for sustained viability of the Stipa steppes in the next 50-100 years.

Climatic suitability and spatial distribution for summer maize cultivation in China at 1.5 and 2.0 °C global warming.

Evaluating climatic suitability of crop cultivation lays a foundation for agriculture coping with climate change scientifically. Herein, we analyse changes in the climatically suitable distribution of summer maize cultivation in China at 1.5 °C (GW1.5) and 2.0 °C (GW2.0) global warming in the future according to the temperature control targets set by the Paris Agreement. Compared with the reference period (1971-2000), the summer maize cultivation climatically suitable region (CSR) in China mainly shifts eastwards, and its acreage significantly decreases at both GW1.5 and GW2.0. Despite no dramatic changes in the CSR spatial pattern, there are considerable decreases in the acreages of optimum and suitable regions (the core of the main producing region), indicating that half-a-degree more global warming is unfavourable for summer maize production in China's main producing region. When the global warming threshold increases from GW1.5 to GW2.0, the centres-of-gravity of optimum areas shift northeastward under RCP4.5 and RCP8.5, the centres-of-gravity of both suitable and less suitable areas shift northwestward, though the northward trend is more prominent for the less suitable areas, and the centre-of-gravity of unsuitable areas shifts southeastward. Generally, half-a-degree more global warming drives the cultivable areas of summer maize to shift northward in China, while the west region shows a certain potential for expansion of summer maize cultivation.

Applicability of common stomatal conductance models in maize under varying soil moisture conditions.

In the context of climate warming, the varying soil moisture caused by precipitation pattern change will affect the applicability of stomatal conductance models, thereby affecting the simulation accuracy of carbon-nitrogen-water cycles in ecosystems. We studied the applicability of four common stomatal conductance models including Jarvis, Ball-Woodrow-Berry (BWB), Ball-Berry-Leuning (BBL) and unified stomatal optimization (USO) models based on summer maize leaf gas exchange data from a soil moisture consecutive decrease manipulation experiment. The results showed that the USO model performed best, followed by the BBL model, BWB model, and the Jarvis model performed worst under varying soil moisture conditions. The effects of soil moisture made a difference in the relative performance among the models. By introducing a water response function, the performance of the Jarvis, BWB, and USO models improved, which decreased the normalized root mean square error (NRMSE) by 15.7%, 16.6% and 3.9%, respectively; however, the performance of the BBL model was negative, which increased the NRMSE by 5.3%. It was observed that the models of Jarvis, BWB, BBL and USO were applicable within different ranges of soil relative water content (i.e., 55%-65%, 56%-67%, 37%-79% and 37%-95%, respectively) based on the 95% confidence limits. Moreover, introducing a water response function, the applicability of the Jarvis and BWB models improved. The USO model performed best with or without introducing the water response function and was applicable under varying soil moisture conditions. Our results provide a basis for selecting appropriate stomatal conductance models under drought conditions.

Sequence of Changes in Maize Responding to Soil Water Deficit and Related Critical Thresholds.

The sequence of changes in crop responding to soil water deficit and related critical thresholds are essential for better drought damage classification and drought monitoring indicators. This study was aimed to investigate the critical thresholds of maize growth and physiological characteristics responding to changing soil water and to reveal the sequence of changes in maize responding to soil water deficit both in seedling and jointing stages based on 2-year's maize field experiment responding to six initial soil water statuses conducted in 2013 and 2014. Normal distribution tolerance limits were newly adopted to identify critical thresholds of maize growth and physiological characteristics to a wide range of soil water status. The results showed that in both stages maize growth characteristics related to plant water status [stem moisture content (SMC) and leaf moisture content (LMC)], leaf gas exchange [net photosynthetic rate (Pn), transpiration rate (Tr), and stomatal conductance (Gs)], and leaf area were sensitive to soil water deficit, while biomass-related characteristics were less sensitive. Under the concurrent weather conditions and agronomic managements, the critical soil water thresholds in terms of relative soil moisture of 0-30 cm depth (RSM) of maize SMC, LMC, net Pn, Tr, Gs, and leaf area were 72, 65, 62, 60, 58, and 46%, respectively, in seedling stage, and 64, 64, 51, 53, 48, and 46%, respectively, in jointing stage. It indicated that there is a sequence of changes in maize responding to soil water deficit, i.e., their response sequences as soil water deficit intensified: SMC ≥ LMC > leaf gas exchange > leaf area in both stages. This sequence of changes in maize responding to soil water deficit and related critical thresholds may be better indicators of damage classification and drought monitoring.