Winter wheat yield improvement by genetic gain across different provinces in China

The replacement of winter wheat varieties has contributed significantly to yield improvement worldwide,with remarkable progress in China.Drawing on two sets of data,production yield from the National Bureau of Statistics of China and experimental yield from literature,this study aims to(1)illustrate the increasing patterns of production yield among different provinces from 1978 to 2018 in China,(2)explore the genetic gain in yield and yield relevant traits through the variety replacement based on experimental yield from 1937 to 2016 in China,and(3)compare the yield gap between experimental yield and production yield.The results show that both the production and experimental yields significantly increased along with the variety replacement.The national annual yield increase ratio for the production yield was 1.67%from 1978 to 2018,varying from 0.96%in Sichuan Province to 2.78%in Hebei Province;such ratio for the experimental yield was 1.13%from 1937 to 2016.The yield gap between experimental and production yields decreased from the 1970s to the 2010s.This study reveals significant increases in some yield components consequent to variety replacement,including thousand-grain weight,kernel number per spike,and grain number per square meter;however,no change is shown in spike number per square meter.The biomass and harvest index consistently and significantly increased,whereas the plant height decreased significantly.

The first factor affecting dryland winter wheat grain yield under various mulching measures: Spike number

Water is the key factor limiting dryland wheat grain yield.Mulching affects crop yield and yield components by affecting soil moisture.Further research is needed to determine the relationships between yield components and soil moisture with yield,and to identify the most important factor affecting grain yield under various mulching measures.A long-term 9-yearifeld experiment in the Loess Plateau of Northwest China was carried out with three treatments:no mulch (CK),plastic mulch (M_(P)) and straw mulch (M_(S)).Yield factors and soil moisture were measured,and the relationships between them were explored by correlation analysis,structural equation modeling and significance analysis.The results showed that compared with CK,the average grain yields of M_(P) and M_(S) increased by 13.0and 10.6%,respectively.The average annual grain yield of the M_(P) treatment was 134 kg ha^(–1) higher than the M_(S) treatment.There were no significant differences in yield components among the three treatments (P<0.05).Soil water storage of the M_(S) treatment was greater than the M_(P) treatment,although the differences were not statistically signifiant.Soil water storage during the summer fallow period (SWSSF) and soil water storage before sowing (SWSS) of M_(S) were significantly higher than in CK,which increased by 38.5 and 13.6%,respectively.The relationship between M_(P) and CK was not statistically significant for SWSSF,but the SWSS in M_(P) was significantly higher than in CK.In terms of soil water storage after harvest (SWSH) and water consumption in the growth period(ET),there were no signi?cant differences among the three treatments.Based on the three analysis methods,we found that spike number and ET were positively correlated with grain yield.However,the relative importance of spike number to yield was the greatest in the M_(P )and M_(S) treatments,while that of ET was the greatest in CK.Suifcient SWSSF could indirectly increase spike number and ET in the three treatments.Based on these results,mulch can improve yield and soil water storage.The most important factor affecting the grain yield of dryland wheat was spike number under mulching,and ET with CK.These findings may help us to understand the main factors influencing dryland wheat grain yield under mulching conditions compared to CK.

Spectral purification improves monitoring accuracy of the comprehensive growth evaluation index for film-mulched winter wheat

In order to further improve the utility of unmanned aerial vehicle(UAV)remote-sensing for quickly and accurately monitoring the growth of winter wheat under film mulching, this study examined the treatments of ridge mulching,ridge–furrow full mulching, and flat cropping full mulching in winter wheat.Based on the fuzzy comprehensive evaluation (FCE) method, four agronomic parameters (leaf area index, above-ground biomass, plant height, and leaf chlorophyll content) were used to calculate the comprehensive growth evaluation index (CGEI) of the winter wheat, and 14 visible and near-infrared spectral indices were calculated using spectral purification technology to process the remote-sensing image data of winter wheat obtained by multispectral UAV.Four machine learning algorithms, partial least squares, support vector machines, random forests, and artificial neural network networks(ANN), were used to build the winter wheat growth monitoring model under film mulching, and accuracy evaluation and mapping of the spatial and temporal distribution of winter wheat growth status were carried out.The results showed that the CGEI of winter wheat under film mulching constructed using the FCE method could objectively and comprehensively evaluate the crop growth status.The accuracy of remote-sensing inversion of the CGEI based on the ANN model was higher than for the individual agronomic parameters, with a coefficient of determination of 0.75,a root mean square error of 8.40, and a mean absolute value error of 6.53.Spectral purification could eliminate the interference of background effects caused by mulching and soil, effectively improving the accuracy of the remotesensing inversion of winter wheat under film mulching, with the best inversion effect achieved on the ridge–furrow full mulching area after spectral purification.The results of this study provide a theoretical reference for the use of UAV remote-sensing to monitor the growth status of winter wheat with film mulching.

Prediction of the potential distribution and analysis of the freezing injury risk of winter wheat on the Loess Plateau under climate change

Determining the suitable areas for winter wheat under climate change and assessing the risk of freezing injury are crucial for the cultivation of winter wheat.We used an optimized Maximum Entropy(MaxEnt)Model to predict the potential distribution of winter wheat in the current period(1970-2020)and the future period(2021-2100)under four shared socioeconomic pathway scenarios(SSPs).We applied statistical downscaling methods to downscale future climate data,established a scientific and practical freezing injury index(FII)by considering the growth period of winter wheat,and analyzed the characteristics of abrupt changes in winter wheat freezing injury by using the Mann-Kendall(M-K)test.The results showed that the prediction accuracy AUC value of the MaxEnt Model reached 0.976.The minimum temperature in the coldest month,precipitation in the wettest season and annual precipitation were the main factors affecting the spatial distribution of winter wheat.The total suitable area of winter wheat was approximately 4.40×10^(7)ha in the current period.In the 2070s,the moderately suitable areas had the greatest increase by 9.02×10^(5)ha under SSP245 and the least increase by 6.53×10^(5)ha under SSP370.The centroid coordinates of the total suitable areas tended to move northward.The potential risks of freezing injury in the high-latitude and-altitude areas of the Loess Plateau,China increased significantly.The northern areas of Xinzhou in Shanxi Province,China suffered the most serious freezing injury,and the southern areas of the Loess Plateau suffered the least.Environmental factors such as temperature,precipitation and geographical location had important impacts on the suitable area distribution and freezing injury risk of winter wheat.In the future,greater attention should be paid to the northward boundaries of both the winter wheat planting areas and the areas of freezing injury risk to provide the early warning of freezing injury and implement corresponding management strategies.

Improved simulation of winter wheat yield in North China Plain by using PRYM-Wheat integrated dry matter distribution coefficient

The accurate simulation of regional-scale winter wheat yield is important for national food security and the balance of grain supply and demand in China.Presently,most remote sensing process models use the“biomass×harvest index(HI)”method to simulate regional-scale winter wheat yield.However,spatiotemporal differences in HI contribute to inaccuracies in yield simulation at the regional scale.Time-series dry matter partition coefficients(Fr)can dynamically reflect the dry matter partition of winter wheat.In this study,Fr equations were fitted for each organ of winter wheat using site-scale data.These equations were then coupled into a process-based and remote sensingdriven crop yield model for wheat(PRYM-Wheat)to improve the regional simulation of winter wheat yield over the North China Plain(NCP).The improved PRYM-Wheat model integrated with the fitted Fr equations(PRYM-Wheat-Fr)was validated using data obtained from provincial yearbooks.A 3-year(2000-2002)averaged validation showed that PRYM-Wheat-Fr had a higher coefficient of determination(R^(2)=0.55)and lower root mean square error(RMSE=0.94 t ha^(-1))than PRYM-Wheat with a stable HI(abbreviated as PRYM-Wheat-HI),which had R^(2) and RMSE values of 0.30 and 1.62 t ha^(-1),respectively.The PRYM-Wheat-Fr model also performed better than PRYM-Wheat-HI for simulating yield in verification years(2013-2015).In conclusion,the PRYM-Wheat-Fr model exhibited a better accuracy than the original PRYM-Wheat model,making it a useful tool for the simulation of regional winter wheat yield.

A combination of straw incorporation and polymer-coated urea offsets soil ammonia and nitrous oxide emissions in winter wheat fields

The combined effects of straw incorporation(SI)and polymer-coated urea(PCU)application on soil ammonia(NH_(3))and nitrous oxide(N_(2)O)emissions from agricultural fields have not been comprehensively evaluated in Northwest China.We conducted a two-year field experiment to assess the effects of combining SI with either uncoated urea(U)or PCU on soil NH_(3)emissions,N_(2)O emissions,winter wheat yields,yield-scaled NH_(3)(/NH_(3)),and yield-scaled N_(2)O(/N_(2)O).Five treatments were investigated,no nitrogen(N)fertilizer(N_(0)),U application at 150 kg N ha-1 with and without SI(SI+U and S_(0)+U),and PCU application at 150 kg N ha^(-1) with and without SI(SI+PCU and S_(0)+PCU).The results showed that the NH_(3);emissions increased by 20.98-34.35%following Sl compared to straw removal,mainly due to increases in soil ammonium(NH_(4)^(+)-N)content and water-flled pore space(WFPS).SI resulted in higher N_(2)O emissions than under the So scenario by 13.31-49.23%due to increases in soil inorganic N(SIN)contents,WFPS,and soil microbial biomass.In contrast,the PCU application reduced the SIN contents compared to the U application,reducing the NH_(3)and N_(2)O emissions by 45.99-58.07 and 18.08-53.04%,respectively.Moreover,no significant positive effects of the SI or PCU applications on the winter wheat yield were observed.The lowest /NH_(3) and /N_(2)O values were observed under the S_(0)+PCU and SI+PCU treatments.Our results suggest that single PCU applications and their combination with straw are the optimal agricultural strategies for mitigating gaseous N emissions and maintaining optimal winter wheat yields in Northwest China.

Winter Wheat Yield Estimation Based on Sparrow Search Algorithm Combined with Random Forest:A Case Study in Henan Province,China

Precise and timely prediction of crop yields is crucial for food security and the development of agricultural policies.However,crop yield is influenced by multiple factors within complex growth environments.Previous research has paid relatively little attention to the interference of environmental factors and drought on the growth of winter wheat.Therefore,there is an urgent need for more effective methods to explore the inherent relationship between these factors and crop yield,making precise yield prediction increasingly important.This study was based on four type of indicators including meteorological,crop growth status,environmental,and drought index,from October 2003 to June 2019 in Henan Province as the basic data for predicting winter wheat yield.Using the sparrow search al-gorithm combined with random forest(SSA-RF)under different input indicators,accuracy of winter wheat yield estimation was calcu-lated.The estimation accuracy of SSA-RF was compared with partial least squares regression(PLSR),extreme gradient boosting(XG-Boost),and random forest(RF)models.Finally,the determined optimal yield estimation method was used to predict winter wheat yield in three typical years.Following are the findings:1)the SSA-RF demonstrates superior performance in estimating winter wheat yield compared to other algorithms.The best yield estimation method is achieved by four types indicators’composition with SSA-RF)(R^(2)=0.805,RRMSE=9.9%.2)Crops growth status and environmental indicators play significant roles in wheat yield estimation,accounting for 46%and 22%of the yield importance among all indicators,respectively.3)Selecting indicators from October to April of the follow-ing year yielded the highest accuracy in winter wheat yield estimation,with an R^(2)of 0.826 and an RMSE of 9.0%.Yield estimates can be completed two months before the winter wheat harvest in June.4)The predicted performance will be slightly affected by severe drought.Compared with severe drought year(2011)(R^(2)=0.680)and normal year(2017)(R^(2)=0.790),the SSA-RF model has higher prediction accuracy for wet year(2018)(R^(2)=0.820).This study could provide an innovative approach for remote sensing estimation of winter wheat yield.yield.

Effects of planting patterns plastic film mulching on soil temperature,moisture, functional bacteria and yield of winter wheat in the Loess Plateau of China

The yield of winter wheat is hindered by drought and low temperature in the Loess Plateau of China.Two common mulching methods to conserve soil moisture,ridge furrows with plastic film mulching (RP) and flat soil surfaces with plastic film mulching (FP) are helpful for wheat production.Our previous study indicated that FP could improve wheat yield more effectively than RP,but the reason remains unclear.The effect of mulching method on functional bacteria also needs to be further studied.In this study,winter wheat was employed to evaluate the impacts of mulching method on soil temperature,moisture content,microorganisms and grain yield.The results showed that FP had a warming effect when the soil temperature was low and a cooling effect when the temperature was too high.However,the ability to regulate soil temperature in the RP method was unstable and varied with year.The lowest negative accumulated soil temperature was found in the FP treatment,which was 20–89 and 43–99%lower than that of the RP and flat sowing with non-film mulching control (NP) treatments,respectively.Deep soil moisture was better transferred to topsoil for wheat growth in the FP and RP treatments than the NP treatment,which made the topsoil moisture in the two treatments (especially FP) more sufficient than that in the NP treatment during the early growing stage of wheat.However,due to the limited water resources in the study area,there was almost no difference between treatments in topsoil water storage during the later stage.The wheat yield in the FP treatment was significantly higher,by 12–16and 23–56%,respectively,than in the RP and NP treatments.Significant positive correlations were observed among the negative accumulated soil temperature,spike number and wheat yield.The Chao1 and Shannon indices in the RP treatment were 17 and 3.9%higher than those in the NP treatment,respectively.However,according to network relationship analysis,the interspecific relationships of bacteria were weakened in the RP treatment.Phosphorus solubilizing,ammonification and nitrification bacteria were more active in the RP than in the FP treatment,and microbes with nitrate reduction ability and plant pathogens were inhibited in the RP treatment,which improved nutrient availability and habitat for wheat.

Integrating a novel irrigation approximation method with a process-based remote sensing model to estimate multi-years'winter wheat yield over the North China Plain

Accurate estimation of regional winter wheat yields is essential for understanding the food production status and ensuring national food security.However,using the existing remote sensing-based crop yield models to accurately reproduce the inter-annual and spatial variations in winter wheat yields remains challenging due to the limited ability to acquire irrigation information in water-limited regions.Thus,we proposed a new approach to approximating irrigations of winter wheat over the North China Plain(NCP),where irrigation occurs extensively during the winter wheat growing season.This approach used irrigation pattern parameters(IPPs)to define the irrigation frequency and timing.Then,they were incorporated into a newly-developed process-based and remote sensing-driven crop yield model for winter wheat(PRYM–Wheat),to improve the regional estimates of winter wheat over the NCP.The IPPs were determined using statistical yield data of reference years(2010–2015)over the NCP.Our findings showed that PRYM–Wheat with the optimal IPPs could improve the regional estimate of winter wheat yield,with an increase and decrease in the correlation coefficient(R)and root mean square error(RMSE)of 0.15(about 37%)and 0.90 t ha–1(about 41%),respectively.The data in validation years(2001–2009 and 2016–2019)were used to validate PRYM–Wheat.In addition,our findings also showed R(RMSE)of 0.80(0.62 t ha–1)on a site level,0.61(0.91 t ha–1)for Hebei Province on a county level,0.73(0.97 t ha–1)for Henan Province on a county level,and 0.55(0.75 t ha–1)for Shandong Province on a city level.Overall,PRYM–Wheat can offer a stable and robust approach to estimating regional winter wheat yield across multiple years,providing a scientific basis for ensuring regional food security.

Retrieval of Winter Wheat Canopy Carotenoid Content with Ground-and Airborne-Based Hyperspectral Data

Accurate assessment of canopy carotenoid content(CC_(x+c)C)in crops is central to monitor physiological conditions in plants and vegetation stress,and consequently supporting agronomic decisions.However,due to the overlap of absorption peaks of carotenoid(C_(x+c))and chlorophyll(C_(a+b)),accurate estimation of carotenoid using reflectance where carotenoid absorb is challenging.The objective of present study was to assess CC_(x+c)C in winter wheat(Triticum aestivum L.)with ground-and aircraft-based hyperspectral measurements in the visible and near-infrared spectrum.In-situ hyperspectral reflectance were measured and airborne hyperspectral data were acquired during major growth stages of winter wheat in five consecutive field experiments.At the canopy level,a remarkable linear relationship(R^(2)=0.95,p<0.001)existed between C_(x+c) and Ca+b,and correlation between CC_(x+c)C and wavelengths within 400 to 1000 nm range indicated that CC_(x+c)C could be estimated using reflectance ranging from visible to near-infrared wavebands.Results of Cx+c assessment based on chlorophyll and carotenoid indices showed that red edge chlorophyll index(CI red edge)performed with the highest accuracy(R^(2)=0.77,RMSE=22.27μg/cm^(2),MAE=4.97μg/cm^(2)).Applying partial least square regression(PLSR)in CC_(x+c)C retrieval emphasized the significance of reflectance within 700 to 750 nm range in CC_(x+c)C assessment.Based on CI red edge index,use of airborne hyperspectral imagery achieved satisfactory results in mapping the spatial distribution of CC_(x+c)C.This study demonstrates that it is feasible to accurately assess CC_(x+c)C in winter wheat with red edge chlorophyll index provided that C_(x+c) correlated well with C_(a+b) at the canopy scale.it is therefore a promising method for CC_(x+c)C retrieval at regional scale from aerial hyperspectral imagery.

Identifying the critical phosphorus balance for optimizing phosphorus input and regulating soil phosphorus effectiveness in a typical winter wheat-summer maize rotation system in North China

Phosphorus(P)is a nonrenewable resource and a critical element for plant growth that plays an important role in improving crop yield.Excessive P fertilizer application is widespread in agricultural production,which not only wastes phosphate resources but also causes P accumulation and groundwater pollution.Here,we hypothesized that the apparent P balance of a crop system could be used as an indicator for identifying the critical P input in order to obtain a high yield with high phosphorus use efficiency(PUE).A 12-year field experiment with P fertilization rates of 0,45,90,135,180,and 225 kg P_(2)O_(5)ha^(-1)was conducted to determine the crop yield,PUE,and soil Olsen-P value response to P balance,and to optimize the P input.Annual yield stagnation occurred when the P fertilizer application exceeded a certain level,and high yield and PUE levels were achieved with annual P fertilizer application rates of 90-135 kg P_(2)O_(5)ha^(-1).A critical P balance range of 2.15-4.45 kg P ha^(-1)was recommended to achieve optimum yield with minimal environmental risk.The critical P input range estimated from the P balance was 95.7-101 kg P_(2)O_(5)ha^(-1),which improved relative yield(>90%)and PUE(90.0-94.9%).In addition,the P input-output balance helps in assessing future changes in Olsen-P values,which increased by 4.07 mg kg^(-1)of P for every 100 kg of P surplus.Overall,the P balance can be used as a critical indicator for P management in agriculture,providing a robust reference for limiting P excess and developing a more productive,efficient and environmentally friendly P fertilizer management strategy.

Plastic mulch increases dryland wheat yield and water-use productivity,while straw mulch increases soil water storage

Amplifying drought stress and high precipitation variability impair dryland wheat production.These problems can potentially be minimized by using plastic mulch(PM)or straw mulch(SM).Therefore,wheat grain yield,soil water storage,soil temperature and water-use productivity of PM and SM treatments were compared with no mulch(CK)treatment on dryland wheat over a period of eight seasons.Compared to the CK treatment,PM and SM treatments on average significantly increased grain yield by 12.6 and 10.5%,respectively.Compared to the CK treatment,SM treatment significantly decreased soil daily temperature by 0.57,0.60 and 0.48℃ for the whole seasons,growing periods and summer fallow periods,respectively.In contrast,compared to the CK treatment,PM treatment increased soil daily temperature by 0.44,0.51 and 0.27℃ for the whole seasons,growing periods and summer fallow periods,respectively.Lower soil temperature under SM allowed greater soil water storage than under PM.Soil water storage pre-seeding was 17%greater under the SM than under the PM treatment.Soil water storage post-harvest was similar for the PM and SM treatments,but evapotranspiration was 4.5%higher in the SM than in the PM treatment.Consequently,water-use productivity was 6.6%greater under PM than under the SM treatment.Therefore,PM treatment increased dryland wheat yield and water-use productivity,while straw mulch increased soil water storage.

Studies on the Characteristics of Chlorophyll Fluorescence of Winter Wheat Flag Leaves at Different Developing Stages

The parameters of fluorescence induction kinetics and the maximal light-saturated net CO2 assimilation rate (P-sat) of the flag leaves of four cultivars of winter wheat (Triticum aestivum L.) were compared at three different developing stages for the first time. From the blooming stage to the milky stage, the quantum efficiency of PS II photochemistry (F-v/F-m) declined slightly only at the milk stage. The photochemical quenching co-efficient (qP), actual quantum yield of photosystem II (PS II)electron transport (Phi (PSII)) and P-sat decreased substantially (> 15%), while the non-photochemical quenching co-efficient (qN) increased significantly (> 100%). There existed a linear correlation between the Phi (PSII) and the P-sat (r = 0.918). The results indicate that with the senescence of the flag leaves of winter wheat the photosynthetic efficiency including that of the energy transport and the CO2 assimilation significantly decreased.

Influences of Different UV-B Radiation Treatments in Short Time on Some Physiological Characteristics of Winter Wheat Seedlings

[Objective] studying the influences of different UV-B radiation treatments in short time on some physiological characteristics of winter wheat seedlings was to provide reference for the mechanism of plant response to ultraviolet irradiation in short time. [Method] The winter wheat taken as materials were treated with 15 and 30 pW/cm^2 UV-B radiation, then the physiological indexes such as pigment content and photosynthetic rate were determined. [ Results] The UV-B treatment caused the declines of chlorophyll content, soluble protein content and water content of leaves, besides, dose-effect was existed. The decline of 30 pW/cm^2 treatment was bigger than that of 15 μW/cm^2 treatment. The influences of UV-B radiation on carotenoid content and anthocyanidin content were similar; the change trends were declined firstly then increased. The UVB treatment with two doses restrained the electron transport of PSⅡ, particularly; the inhibitory effect was biggest after treated 2 h, and then this effect was declined in 4, 6 and 8 h, so the dose-effect was existed. The UV-B radiation with two doses restricted photosynthetic rate and the inhibitory effect increased with the increase of treatment time. The high dose treatment caused huge damage to membrane system, while the result of low dose treatment was not obvious. [ Conclusion] UV-B radiation treatment had dose-effect on winter wheat seedlings in short time and the influence of high dose was bigger than that of low dose. With the increase of treatment time, the damage was alleviated; besides, the result was not similar to that of UV-B radiation in long time.

Effects of Concentration of NO_3^--N on Root Vigor and Rhizosphere pH of Winter Wheat Seedlings

[Objective] The aim was to research the effect of concentration of NO-3-N on root vigor and rhizosphere pH of winter wheat seedlings under water culture.[Method]By selecting Hoagland's nutritional solution as cultural medium and winter wheat as material of experiment,on the basis,testing root vigor,nutrient solution NO-3 and change of pH values under the different level of disposal,such as high(containing NO-3-N 15 mmol/L),medium(containing NO-3-N 7.5 mmol/L)and lower(containing NO-3-N 2.5 mmol/L).[Result]The results of this research showed that the effect of different nitrogen level on the wastage of nutrient solution NO-3,the changes of pH values and root vigor is obvious under the hydroponics condition.[Conclusion]Though NO-3 is a safe nitrogen sources when it was supplied to plants too more,it would restrain assimilation on nitrate nitrogen farther,but when it was supplied to plants too little,it would lead to deficiency of NO-3 that plants uptake and decrease of root activity,so it isn't useful to wheat young seedling to absorb nitrogen nutrition.

Effect of Heat Stress on Photosynthetic Characteristics of Different Green Organs of Winter Wheat During Grain-filling Stage

Four winter wheat (Triticum aestivum L.) varieties ('JD 8', 'Jing 411','Centurk' and 'Tam 202') were used to study the effect of heat stress on photosynthetic characteristics of flag leaf blade, nag leaf sheath, peduncle, glume, lemma and awn during grain-filling stage. The results showed that heat acclimation during grain-filling stage increased thermotolerance of wheat with significant differences among different green organs. During heat stress, the decreases of the efficiency of primary light energy conversion (F-v/F-m) of PS II and pigment (chlorophyll and carotenoid) content were much slower in peduncle, flag leaf sheath and glume than in nag leaf blade, lemma and ann; and the percentage of decrease in net photosynthetic rate (P-n) of ear was lower than that of the nag leaf blade. The measured photosynthetic parameters (F-v/F-m, P-n and pigment content) of 'JD 8', a relatively heat tolerant variety, declined more slowly than those of the other three varieties during the whole heat stress period.

Effects of Photoinhibition and Its Recovery on Photosynthetic Functions of Winter Wheat Under Salt Stress

Effects of photoinhibition and its recovery on photosynthetic functions of winter wheat (Triticum aestivum L.) under salt stress were studied. The results showed that several parameters associated with PSⅡ functions, e.g. Fv/Fo?Fv/Fm and qP were not influenced by lower salt concentration (200 mmol/L NaCl) while CO 2 assimilation rate decreased significantly. When exposed to higher salt concentration (400 mmol/L NaCl), PSⅡ functions were significantly inhibited which led to the decrease of carbon assimilation. These results suggest that different concentrations of salt stress affected photosynthesis by different modes. Salt stress made photosynthesis more sensitive to strong light and led to more serious photoinhibition. Under lower concentration of salt stress, the Q B-non-reductive PSⅡ reaction centers formed at the beginning of photoinhibition could be effectively used to compose active PSⅡ reaction center (RC) and repair the reversible inactivated PSⅡ RC. Under higher concentration of salt stress, PSⅡ reaction centers were seriously damaged during photoinhibition, the Q B-non-reductive PSⅡ RC could only be partly effective at the early time of photoinhibition, thus led to the accumulation of Q B-non-reductive PSⅡ RC in the course of restoration under dim light.

Effects of Sulfur Fertilizer Application Methods on Grain Protein Content During Filling Stage of Winter Wheat

[ Objective] The experiment aimed to provide a theoretical base of optimal cultivation management for the high yield and good quality and high efficiency of winter wheat. [ Method] The effects of two sulfur fertilizer application methods on dynamic changes of grain protein content and glutenin content of Yumai 49 and Yumai 66 during wheat grain filling stage were studied under the field conditions. [Result] Both the grain protein and glutenin content of two cultivars were increased by sulfur fertilizer, particularly, the effects on Yumai 49 were more significant.[ Conclusion] The grain content and glutenin content of different wheat cultivars could be increased by taking different sulfur fertilizer application methods.

Application of EOS/MODIS-NDVI at Different Time Sequences on Monitoring Winter Wheat Acreage in Henan Province

[Objective] Calculation of winter wheat acreage in Henan Province using EOS/MODIS-NDVI data at different time sequences. [Method] After process of EOS/MODIS images, geographical adjustment, wave band combination, normal difference vegetation index (NDVI) was obtained. Based on the wide spectrum measurement, the processed data were supervisedly classified, thus the acreage of winter wheat in Henan Province in 2005 was acquired. [Result] Total 92208 pixels were observed for the winter wheat in Henan Province, and the plantation acreage was 5 760 thousand hm2. Compared with the data from statistical department, the error of this method was about 9.66%. [Conclusion] The method introduced in the present study could be applied in monitoring winter wheat acreage.

The Division Method of Winter Wheat Drought Risk Zones in Hebei-Shandong-Henan under Irrigation Conditions

The average rainfall in whole growth period of winter wheat to plus or minus several times of sample variance was used to define different grades of drought.The reduction rate of production in meteorological which was equal to or greater than the rate of 3% was taken as standards to define wheat drought disaster years.The average reduction ratio of production in the wheat drought years in Hebei-Shandong-Henan was calculated.The frequency distribution rule of wheat in different drought disaster strength of winter wheat in Hebei-Shandong-Henan was analyzed.According to the conception and calculation method of drought disaster risk index of winter wheat,the regional distribution law of drought disaster risk index of winter wheat was analyzed.The division technical methods of winter wheat drought disaster risk zones in Hebei-Shandong-Henan under the irrigated conditions were put forward.Taking the average reduction rate of production in drought years,drought disaster risk index and precipitation of winter wheat in growth periods as indices,using the statistical analysis and overlay function of GIS,the production reduction risk of winter wheat caused by drought disaster in winter wheat zones of Hebei-Shandong-Henan was divided and evaluated.The risk evaluation of production reduction of winter wheat in different risk zones under different climate conditions was realized.The disaster prevention and mitigation measures of winter wheat drought were given.