Genome-Wide Association Study on Seedling Phenotypic Traits of Wheat under Different Nitrogen Conditions.

Nitrogen fertilizer input is the main determinant of wheat yield, and heavy nitrogen fertilizer application causes serious environmental pollution. It is important to understand the genetic response mechanism of wheat to nitrogen and select wheat germplasm with high nitrogen efficiency. In this study, 204 wheat species were used to conduct genome-wide association analysis. Nine phenotypic characteristics were obtained at the seedling stage in hydroponic cultures under low-, normal, and high-nitrogen conditions. A total of 765 significant loci were detected, including 438, 261, and 408 single nucleotide polymorphisms (SNPs) associated with high-, normal, and low-nitrogen conditions, respectively. Among these, 14 SNPs were identified under three conditions, for example, AX-10887638 and AX-94875830, which control shoot length and root-shoot ratio on chromosomes 6A and 6D, respectively. Additionally, 39 SNPs were pleiotropic for multiple traits. Further functional analysis of the genes near the 39 SNPs shows that some candidate genes play key roles in encoding proteins/enzymes, such as transporters, hydrolases, peroxidases, glycosyltransferases, oxidoreductases, acyltransferases, disease-resistant proteins, ubiquitin ligases, and sucrose synthetases. Our results can potentially be used to develop low-nitrogen-tolerant species using marker-assisted selection and provide a theoretical basis for breeding efficient nitrogen-using wheat species.

Responses of root characteristics and nitrogen absorption and assimilation to different pH gradients of winter wheat at seedling stage.

Nitrogen (N) and rhizosphere pH are the two main factors restricting the growth of winter wheat (Triticum aestivum L.) in North China Plain. Soil nutrient availability is affected by soil acidity and alkalinity. In order to understand the effect of rhizosphere pH value on wheat nitrogen metabolism and the response of wheat growth to pH value at seedling stage, winter wheat varieties 'Aikang 58' (AK58) and 'Bainong 4199' (BN4199) were tested in hydroponics under three pH treatments (pH = 4.0, 6.5, and 9.0). The results showed that the accumulation of dry matter in root and above ground under pH 4.0 and pH 9.0 treatments was lower than that under pH 6.5 treatments, and the root/shoot ratio increased with the increase of pH value. Regardless of pH value, 'BN4199' had higher root dry weight, root length, root surface area, root activity and root tip than 'AK58'. Therefore, wheat that is tolerant to extreme pH is able to adapt to the acid-base environment by changing root characteristics. At pH 4.0, the net H+ outflow rate of wheat roots was significantly lower than that of the control group, and the net NO3- flux of wheat roots was also low. The net H+ outflow occurred at pH 6.5 and 9.0, and at the same time, the net NO3- flux of roots also increased, and both increased with the increase of pH. The activity of nitrate reductase (NR) in stem of pH 9.0 treatment was significantly higher than that of other treatments, while the activity of glutamine synthetase (GS) in root and stem of pH 6.5 treatment was significantly higher than that of other treatments. Under pH 4.0 and pH 9.0 treatments, the activities of NR and GS in 'BN4199' were higher than those in 'AK58', The root respiration of 'BN4199' was significantly higher than that of 'AK58' under pH 4.0 and pH 9.0 treatment, and 'BN4199' had higher NO3- net flux, key enzyme activity of root nitrogen metabolism and root respiration. Therefore, we believe that 'BN4199' has strong resistance ability to extreme pH stress, and high root/shoot ratio and strong root respiration can be used as important indicators for wheat variety screening adapted to the alkaline environment at the seedling stage.

The health benefits of bicycling to school among adolescents in China: A propensity score matching study.

Background: A large number of high-income countries are now promoting active commuting to school as an opportunity for adolescents to increase physical activity (PA) and improve their health. Few studies have examined the multiple benefits of active travel to school among adolescents in developing countries, especially in China. Hence, this study aims to estimate the effects of bicycling to school on adolescents' subjective health, physical health, and sickness absence. Methods: Self-reported and cross-sectional data from 6,353 school-aged children (12-19 years old) in the 2014-2015 China Education Panel Survey (CEPS2014-2015) were used. The independent variable was a binary, self-reported indicator of whether children bicycled to school. The dependent variables included subjective health (self-reported health, mental stress), physical health (BMI, kidney disease, lung disease, heart disease, brain disease, upper limb fracture, lower limb fracture, and sickness frequency), and sickness absence. Propensity score matching (PSM) was used to estimate the causal effects of bicycling to school on adolescents' health. Results: Bicycling to school positively affects both subjective and physical health. Those students who biked to school were associated with a higher self-rated health status, a healthier weight, a lower level of mental stress, and a lower risk of developing brain diseases. No significant relation is found between bicycling and sickness frequency, and sickness absence. Moreover, we separately compared the bicycling group with the walking group and the non-active travel group. There is still evidence that cycling is beneficial for students. Compared with walking to school, cycling to school resulted in a higher self-rated health score and a lower mental stress score. Physically, students who bicycled to school were less likely to be absent from school and suffer from kidney and brain diseases than students who walked to school. However, we do not find a significant difference in health outcomes from cycling compared to non-active modes of transportation. Further, differentiation of the health effects of bicycling across living areas shows that health effects are more pronounced for those living in edge and rural areas. Conclusion: These findings provide evidence of the value of promoting bicycling to school in improving various adolescents' health outcomes in transitional China.

The Impact of Urban Rail Transit Epidemic Prevention Measures on Passengers' Safety Perception.

In 2020, COVID-19 triggered concern about the safety of public transport. To meet passengers' expectations regarding safety, the public transport department has stepped up its pandemic prevention services. Some prevention services require passengers to follow mandatory requirements. However, whether and to what extent these requirements affect passenger satisfaction with public transportation services remains unclear. This study aims to construct an integrated framework to explore the direct and indirect relationships between four constructs (regular services quality, pandemic prevention service, psychological distance, and safety perception) and passengers' satisfaction in the context of urban rail transit services. Based on survey data collected from 500 passengers on the Shanghai Metro, this paper examines the relationships between routine service, pandemic prevention measures, safety perceptions, and satisfaction with the service. The results from the structural equation model indicate that routine service (0.608), pandemic prevention measures (0.56), and safety perception (0.05) have positive effects on passenger satisfaction. Psychological distance negatively impacts safety perception (-0.949) and has indirect effects on passenger satisfaction. Further, in order to identify the service improvements that public transportation departments should focus on, we use the three-factor theory to identify the services that should be improved: Basic factors, such as "punctual arrival of metros", "treatment of harmful garbage", "increasing frequency of platform disinfection", and "measurement of station temperature" should be treated as the first priority. As the second improvement priority, "the planning of metro stations can accommodate my travel scope" can be considered. Last, public transportation departments can enhance the exciting factor by installing "metro entrance signs" when resources are available.

How School Travel Affects Children's Psychological Well-Being and Academic Achievement in China.

Previous research on the role of school travel in children's well-being (WB) has paid little attention to developing countries. Using national survey data across China, this study examines how children's psychological well-being (PWB) and academic performance differ across commute duration and mode among urban, rural, and urban fringe areas. Our findings show that commute times are significantly negatively associated with children's PWB and academic achievements, and this correlation varies across areas. Children living in the urban fringe have the longest average one-way commuting time (18.6 min), but they have a better acceptance of longer commuting duration, whereas commuting time is more influential in the city center and rural areas. Regarding travel mode, walking to school is positively associated with PWB in the center area, while bicycles and public transport positively affect the rural student scores. Results from quantile regression show that students on the lower quantiles of the conditional distribution of PWB tend to suffer more than the others when commuting time increases; students with middle scores respond similarly to marginal changes in commuting time. Recommendations for urban planners and policymakers to enhance child WB include fostering school-home balance, improving public transit services, and investing in pedestrian and bicycle infrastructure for those vulnerable groups.

A novel wheat lodging resistance evaluation method and device based on the thrust force of the stalks.

Wind speed is the most essential factor causing wheat lodging. Accurate understanding of the wind speed characteristics at near-surface layer of wheat fields and its effect on lodging is the basis of objective evaluation of wheat lodging resistance. In this paper, the characteristics of wind speed at the near-surface layer of wheat fields and their impact on lodging were studied. A new device was proposed for directly measuring the critical thrust force of wheat population lodging resistance in the field based on the black box method. A novel wheat stem lodging resistance evaluation method/model was established based on the critical thrust force of wheat population stem lodging and the wind speed characteristics of field near-surface layer. The method used the lodging critical wind speed as the index of wheat lodging resistance, which was verified by wind tunnel and field experiment. The results showed that there was a significant positive correlation between the critical wind speed of wheat lodging resistance and its critical thrust force. The values of wheat canopy apparent roughness length, wind attack angle, ventilation coefficient and other wind field characteristics had important effects on the calculation of wheat lodging resistance critical wind speed. The method can eliminate bias when calculating wheat lodging resistance by considering only one or a few indicators and the results of field lodging evaluation were consistent with those of field lodging survey. The method is simple and can be used to assess the lodging resistance of wheat, select extension regions for wheat varieties, and evaluate lodging factors in the field.

Influence of Speed and Rainfall on Large-Scale Wheat Lodging from 2007 to 2014 in China.

Strong wind and heavy rain remain the two most important causes of large acreage wheat (Triticum aestivum L.) lodging in China. For research the influence of wind speed and rainfall-separately as well as together-on the extent and degree of lodging, five levels of the severity of lodging were defined based on a combination of the lodging area and the degree of tilting. Detailed meteorological information was studied on 52 instances of large-scale lodging that occurred from 2007 to 2014. The results showed that strong wind's lodging accounted for 8% of the instances studied, continuous rainfall's lodging accounted for 19% and strong winds-heavy rainfall's accounted for 73%. The minimum instantaneous wind speed that could cause large-scale lodging was closely related to rainfall. Without rainfall, the wind speed that resulted in lodging ranging in severity from slight to severe (Level 2 to Level 5) was 14.9 m/s, 19.3 m/s, 21.5 m/s, and 26.5 m/s, respectively; when accompanied by rainfall, the wind speed that resulted in lodging of the same severity decreased linearly with the increase of rainfall. These results will be particularly useful in preventing and alleviating wheat lodging as well screening wheat varieties with good lodging resistance.

[Effects of harvest date on quality of BNS hybrid wheat flour and steamed bread].

Three wheat hybrids derived from the BNS male sterile line were used to study the effect of harvest time on gluten content, dough rheological properties, starch pasting properties of wheat flour and the quality of steamed bread. Each of the three hybrids was harvested at May 27, May 31 and June 4, respectively. The results showed that the flour quality of BNS hybrids was affected by harvest time to some extents, and the best harvest time varied among the different hybrids. For Baiza 1, Baiza 2 and Baiza 3, the best harvest time was May 27, May 27 and June 4, respectively. Both the flour quality and the comprehensive score and taste of steamed bread were the best for the hybrids harvested at these dates. Moreover, Baiza 2 was suited to make steamed bread and noodle when harvested on May 27.

[Effects of 5-aminolevulinic acid on winter wheat dry matter accumulation after anthesis and flag leaf senescence].

Taking wheat cultivar Bainong AK58 as test material, a field experiment was conducted to study the effects of different concentration 5-aminolevulinic acid (ALA) (0,10, 30 and 50 mg x L(-1)) applied at initial heading stage on the post-anthesis dry matter accumulation and flag leaf senescence of the cultivar. Applying 10-50 mg x L(-1) of ALA benefited the dry matter accumulation, with its total amount at maturing stage being significantly higher than that of the control (0 mg x L(-1) ALA). 10-50 mg x L(-1) of ALA had no significant effects on the distribution of accumulated dry matter in leaf, stem and sheath, and grain, but increased the contribution of the dry matter to grain yield. 10-50 mg x L(-1) of ALA increased the leaf area index at milky and dough stages, but had no effects on it at flowering stage. After treated with 10-50 mg x L(-1) ALA, the leaf SPAD value and net photosynthetic rate from anthesis to milky stage were significantly higher, and the MDA content and relative electric conductivity at later grain-filling stage were lower, compared with those of the control. Applying 10-50 mg x L(-1) of ALA increased the grain number per spike, 1000-grain mass, and grain yield significantly, with the best effect when applying 30 mg x L(-1) ALA.