Effects of Heat Stress during Seed Filling Stage on Brassica napus Seed Oil Accumulation and Chlorophyll Fluorescence Characteristics

As global temperature rise,the threat of heat stress to rapeseed production is becoming more obvious.Exploring the response characteristics of two important biological pathways,oil accumulation and photosynthesis,to heat stress during B.napus seed filling is helpful in the genetic improvement of heat-tolerant rapeseed.The effects of heat stress on seed oil accumulation and chlorophyll fluorescence characteristics of 29 B.napus germplasms with different oil content and environmental sensitivity,including 6 rapeseed varieties which exhibited environmentsensitive/insensitive and with high,medium or low oil content,were tested by whole plant heat stress or the in vitro silique culture system.Both assay exhibited similar trend on oil content of the rapeseed germplasms.The heat effect on the chlorophyll fluorescence kinetic parameters F_(v)/F_(m),ETR and Y(Ⅱ)were also consistent.Heat stress significantly decreased oil content,although there was abundant genetic variation on heat tolerance among the genotypes.Correlation analysis showed that the decrease rate of F_(v)/F_(m) of silique heat-stressed B.napus developing seed was positive correlative to the decrease rate of mature seed oil content of the whole plant heat-stressed rapeseed(R=0.9214,P-value<0.01).Overall,the results indicated that heat stress inhibited oil accumulation and photosynthesis in B.napus developing seed.The decrease rate of chlorophyll fluorescence parameter F_(v)/F_(m) of heat-stressed developing seed could be used as the index of heat tolerant rapeseed identification.Further,two heat insensitive rapeseed varieties with high oil content were identified.

Effects of Lodging at Different Filling Stages on Rice Yield and Grain Quality

The effects of lodging of rice plants from 20 d after full heading to maturity on yield and grain quality were investigated with a hybrid rice combination Liangyoupeijiu and a japonica rice cultivar CY-6. The results showed that, except for brown rice rate, almost all parameters for yield and grain quality including ratio of grain length to grain width, gelatinization temperature and gel consistency, were significantly influenced by lodging and thus deteriorated. Regression analysis suggested that, lodging one day earlier at the grain-filling stage could cause 2.66% to 2.71% of yield loss, 1.8 to 2.6 percentage points decrease of seed-setting rate, 0.26 to 0.32 g reduction of lO00-grain weight, 0.097 to 0. 155 percentage point decline of milled rice rate, as well as 0.13 to 0.27 percentage point increase of chalky grain rate, and 0.021 to 0.024 percentage point rise of protein content, and subsequently lower the eating quality.

Effect of Temperature at Grain Filling Stage on Activities of Key Enzymes Related to Starch Synthesis and Grain Quality of Rice

Three japonica rice varieties with different cooking and eating quality were grown at high temperature in the greenhouse and natural field. Effects of temperature at the grain filling stage on these varieties were investigated in terms of the activities of key enzymes related to starch synthesis and cooking and eating quality of rice grain. The high temperature at the grain filling stage increased protein content, and decreased amylose content and taste meter value of rice; inferior grain quality varieties showed a greater magnitude of the increase or decrease than the superior ones. Reaction of rapid visco analyser profiles to the temperature varied with rice varieties. The activities of adenosine diphosphoglucose pyrophosphoryiase （AGPP）, soluble starch synthase （SSS） and starch branching enzyme （SBE） gradually increased to a peak value, and thereafter declined as grain filling progressed. Enzyme activities in different varieties differed in a same filling stage, and also in the time when the enzyme activity reached a maximum. AGPP and SSS were insensitive to the environmental temperature, but SBE was comparatively sensitive to the temperature, and its activity declined when temperature was too high or too low.

Effect of Different Irrigation Patterns on Transportation and Allocation of Carbohydrate During Grain Filling of Rice

Using intersubspecific hybrid rice Xieyou 9308 and Liangyou Peijiu as the tested materials, the effects of differentirrigation patterns on transportation and allocation of carbohydrate during grain filling stage was observed by the designwith three level of soil water content in irrigated field. The results showed that in the conventional flooding and thealternate dry-watering cultivations, the exported rate of stored carbohydrate from stem and photophate from the leaves were60 and 90 % respectively. The exported rate of carbohydrate was decreased significantly (P<0.01) in the non-floodingcultivation. There was no significant difference between the conventional flooding and dry-wet alternation treatments interm of the exported rate of carbohydrate. The filling grains were the major sinks for carbohydrate storage during grainfilling stage. Grains received nearly 50% of stored carbohydrate from leaf sheath and 80% of photophate from leaves. Atthe nonflooding condition the absorbing rates of grains were significantly decreased by 10 % from leaf sheath and 20 %from leaves photophate. Water stress leaded much decrease in absorbing ability for inferior grains, which might be one ofthe main causes for low seed-settling rate in non-flooding cultivation.

Effect of Drought Stress on Proteome of Maize Grain during Grain Filling

Based on isobaric tags for relative and absolute quantification(iTRAQ)technology,the proteome of grains of a maize cultivar Huangzao 4 under drought stress at grain filling stage was analyzed.The results show that under drought stress,438 proteins were differentially expressed in the maize grains during grain filling.Among them,200 were up-regulated and 238 were down-regulated.The gene ontology(GO)analysis shows that the biological processes in which differential proteins are more involved are cellular processes,metabolic processes and single biological processes;proteins in the cell component category are mainly distributed in cells,cell parts and organelles;and the proteins the molecular function category mainly possess catalytic activity and binding function.Differentially expressed proteins classified by COG are mainly involved in protein post-translational modification and transport,molecular chaperones,general functional genes,translation,ribosomal structure,biosynthesis,energy production and transformation,carbohydrate transport and metabolism,amino acid transport and metabolism,etc.The subcellular structure of the differentially expressed proteins is mainly located in the cell chloroplast and cytosol.The proportions are 35.01%and 30.21%respectively.KEGG metabolic pathway enrichment analysis shows that the differentially expressed proteins are mostly involved in antibiotic biosynthesis,microbial metabolism in different environments,and endoplasmic reticulum protein processing;the metabolic pathways with higher enrichment are the carbon fixation pathway and estrogen signaling pathway of prokaryotes;and the higher enrichment and greater significance are in the tricarboxylic acid cycle,carbon fixation of photosynthetic organisms and proteasome.The results of this study preliminarily reveal the adaptive mechanism of maize grains in response to drought stress during grain filling,providing a theoretical reference for maize drought-resistant molecular breeding.

Non-destructive method of small sample sets for the maize moisture content measurement during filling based on NIRS

In maize breeding,limitations on sampling quantity and associated costs for measuring maize grain moisture during filling are imposed by factors like the planting area of new varieties,maize plant density,effective experimental spikes,and other conditions.However,the conventional method of detecting moisture content in maize grains is slow,damages seeds,and necessitates many sample sets,particularly for high moisture content determination.Thus,a strong demand exists for a non-destructive quantitative analysis model of maize moisture content using a small sample set during grain filling.The Bayes-Merged-Bootstrap(BMB)sample optimization method,which built upon the Bayes-Bootstrap sampling method and the concept of merging,was proposed.A critical concern in dealing with small samples is the relationship between data distribution,minimum sample value,and sample size,which has been thoroughly analyzed.Compared to the Bayes-Bootstrap sample selection method,the BMB method offers distinct advantages in the optimized selection of small samples for non-destructive detection.The quantitative analysis model for maize grain moisture content was established based on the support vector machine regression.Results demonstrate that when the optimal resampling size is 1000 times or more than the original sample size using the BMB method,the model exhibits strong predictive capabilities,with a determination coefficient(R2)>0.989 and a relative prediction determination(RPD)>2.47.The results of the 3 varieties experiment demonstrate the generality of the model.Therefore,it can be applied effectively in practical maize breeding and determining grain moisture content during maize machine harvesting.

Subsoiling and Ridge Tillage Alleviate the High Temperature Stress in Spring Maize in the North China Plain

High temperature stress（HTS） on spring maize（Zea mays L.） during the filling stage is the key factor that limits the yield increase in the North China Plain（NCP）.Subsoiling（SS） and ridge tillage（R） were introduced to enhance the ability of spring maize to resist HTS during the filling stage.The field experiments were conducted during the 2011 and 2012 maize growing seasons at Wuqiao County,Hebei Province,China.Compared with rotary tillage（RT）,the net photosynthetic rate,stomatal conductance,transpiration rate,and chlorophyll relative content（SPAD） of maize leaves was increased by 40.0,42.6,12.8,and 29.7% under SS,and increased by 20.4,20.0,5.4,and 14.2% under R,repectively.However,the treatments reduce the intercellular CO 2 concentration under HTS.The SS and R treatments increased the relative water content（RWC） by 11.9 and 6.2%,and the water use efficiency（WUE） by 24.3 and 14.3%,respectively,compared with RT.The SS treatment increased the root length density and soil moisture in the 0-80 cm soil profile,whereas the R treatment increased the root length density and soil moisture in the 0-40 cm soil profile compared with the RT treatment.Compared with 2011,the number of days with temperatures 33°C was more 2 d and the mean day temperature was higher 0.9°C than that in 2012,whereas the plant yield decreased by 2.5,8.5 and 10.9%,the net photosynthetic rate reduced by 7.5,10.5 and 18.0%,the RWC reduced by 3.9,5.6 and 6.2%,and the WUE at leaf level reduced by 1.8,5.2 and 13.1% in the SS,R and RT treatments,respectively.Both the root length density and the soil moisture also decreased at different levels.The yield,photosynthetic rate,plant water status,root length density,and soil moisture under the SS and R treatments declined less than that under the RT treatment.The results indicated that SS and R can enhance the HTS resistance of spring maize during the filling stage,and led to higher yield by directly improving soil moisture and root growth and indirectly improving plant water status,photosynthesis and grain filling.The study can provide a theoretical basis for improving yield of maize by adjusting soil tillage in the NCP.

Organic Geochemical and Fluid Inclusion Evidence for Filling Stages of Natural Gas and Bitumen in Volcanic Reservoir of Changling Faulted Depression,Southeastern Songliao Basin

Recently,volcanic gas reservoirs in Yaoyingtai （腰英台） and Daerhan （达尔罕） tectonic belts in Changling （长岭） faulted depression of southeastern Songliao （松辽） basin have been discovered.Based on the compositions and isotopic values,the natural gas is characterized by high content of methane,low content of C2＋,and C1/C1-5 beyond 0.95.Also,the natural gas contains nonhydrocarbons including carbon dioxide with the content from 20% to 40% and minor amount of N2.Combined with the isotopic values,the natural gas is generated by humic kerogen and coal-derived type,but in Daerhan,the natural gas is probably mixed by oil type gas.From the measurement of lithology and fluid inclusions in volcanic rocks,the bitumen,liquid hydrocarbon,and gas hydrocarbon inclusions are present.Through the analysis of the single gas inclusion in volcanic reservoir,the content of carbon dioxide is low,so the carbon dioxide and hydrocarbon gas of the reservoirs are not accumulated at the same time.In addition,minor amount of bitumen in the reservoirs is formed by thermal evolution of the crude oils sourced from the Yingcheng （营城） Formation mudstones through the characterizations of the biomarkers.The distribution of homogenization temperatures presents two peaks,one with the liquid hydrocarbon filling stage,and the other with gas filling stage.However,in Daerhan tectonic belt,the second peak is gas and carbon dioxide mixed filling period probably.Combined with the homogenization temperatures of salt water inclusions,the oil and gas filling period is from Qingshankou （青山口） Formation to Nenjiang （嫩江） Formation in the research area.During the charging period,minor amount of inorganic carbon dioxide filled into the trap,but plenty of inorganic carbon dioxide from the end of Sifangtai （四方台） to Eogene periods was related with the structural movement.