Effect of high temperature on the expressions of genes encoding starch synthesis enzymes in developing rice endosperms

High temperature is the major environmental factor affecting grain starch properties of cooking rice cultivars. In this study, two non-waxy indica rice genotypes, cv. 9311 and its mutant with extremely high amylose phenotype（9311eha） were used to study the differential expressions of genes in starch synthesis and their responses to high temperature（HT）. Significant increase in apparent amylose content and hot-water-soluble starch content in mutant 9311 eha were genetically caused by a substitution from AGTTATA to AGGTATA at the leader intron 5′ splice site in Wx gene. This mutation resulted in different m RNA transcript levels, m RNA splicing efficiencies and protein levels of Wx between the two rice genotypes, which also lead to the genotype-dependent alteration in the temporal pattern of Wx transcription and granule-bound starch synthase（GBSS） activity in response to HT. However, changes in the activities of other starch synthesizing enzymes and their expressions of distinct isoform genes were not significant with the Wx gene mutation, thus only minor difference in the particle size of starch granule, chain-length distribution and gelatinization enthalpy were found between the two genotypes. The temporal-specific expression of multiple isoform genes responsive to different temperature regiments indicated that the reduction of GBSS transcript expression under HT was generally accompanied by the decreased expressions of SSSIIa, SSSIIIa and SBEIIb. Consequently, high temperature-ripened grains in 9311 eha showed high proportion of intermediate and long B chains and somewhat lower level of short A chain compared to the wildtype. The temperature-dependent alteration of amylose content was not only attributed to the reduced expression of GBSS, but also associated with the complimentary effect of SSSIIa and SBEIIb.

Transcription factor ZmNAC126 plays an important role in transcriptional regulation of maize starch synthesis-related genes

Maize(Zea mays L.)is one of the most important food crops in the world,and starch is the main component of its endosperm.Transcriptional regulation plays a vital role in starch biosynthesis.However,it is not well understood in maize.We report the identification of the transcription factor ZmNAC126 and its role in regulation of starch synthesis in maize.Transcriptional expression of ZmNAC126 was higher in maize endosperm and kernels than in roots or stems.ZmNAC126 shared a similar expression pattern with starch synthesis genes during seed development,and its expression pattern was also consistent with the accumulation of starch.ZmNAC126 is a typical transcription factor with a transactivation domain between positions 201 and 227 of the amino acid sequence,is located in the nucleus,and binds to CACG repeats in vitro.Yeast one-hybrid assay revealed that ZmNAC126 bound the promoters of ZmGBSSI,ZmSSIIa,ZmSSIV,ZmISA1,and ZmISA2.Transient overexpression of ZmNAC126 in maize endosperm increased the activities of promoters pZmSh2,pZmBt2,pZmGBSSI,pZmSSIIIa,and pZmBT1 but inhibited the activities of pZmISA1 and pZmISA2.ZmNAC126 thus acts in starch synthesis by transcriptionally regulating targeted starch synthesis-related genes in maize kernels.

Changes in Starch Accumulation and Activity of Enzymes Associated with Starch Synthesis of Rice at Different N Supplying Dates

The changes in grain-filling, starch accumulation and activity of enzymes associated with starch synthesis in two different hybrid rice varieties were analyzed at different N supplying dates (earlier-date-emphasized, mean-date-emphasized and later-date- emphasized). The results showed that the N application of later-date-emphasized could promote grain-filling rate, increase grain weight and amylopectin content. The peak of activity in three enzymes of ADPglusoce pyriphosphorylase (ADPG), starch synthesis enzyme (SSS) and starch branching enzyme (SBE) in grains of two different rice varieties was not changed obviously, but the mean and maximum activity of these three enzymes changed, and the changes of SSS and ADPG were bigger than that of SBE as N supplying date changed. The N application of earlier-date-emphasized increased SSS activity and the N application of later-date-emphasized increased ADPG and SBE activities. The mean SSS activity during whole grain-filling period, and ADPG and SBE activities at middle and late period of grain-filling were significantly or very significantly correlated with grain-filling rate and accumulating rate of amylose and amylopectin. Both of ADPG and SBE played an equal important role in the changes of amylose and amylopectin content. The N application of later-date-emphasized increased amylose and amylopectin accumulating rate.

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.

Relationship Between Variation in Activities of Key Enzymes Related to Starch Synthesis During Grain Filling Period and Quality of Eating and Cooking in Rice

Four japonica rice varieties with significant differences in quality of eating and cooking were used in the experiment. The varieties showed differences in amylose and amylopectin contents at different grain filling stages, which were attributed to the accumulative speed of starch at different grain filling stages. During grain filling period, the varieties had no difference in the time when the activities of ADPglocose pyrophosphorylase （AGPP） and soluble starch synthesis （SSS） reached a maximum, but had difference in the time when the activity of starch branching enzyme （SBE） reached a maximum, in which the inferior quality varieties were earlier than the high quality ones, and high quality varieties still kept high enzyme activities at the late stage of grain filling. The correlation and correlative degree between AGPP, SSS, SBE and amylose content, amylopectin content, taste meter value, and RVA properties varied with the different stages of grain filling. The correlation between SSS activity and taste meter value was not significant during the whole period of grain filling, but the activities of AGPP and SBE had significant or highly significant correlation with taste meter value. It was helpful for improving quality of eating and cooking of japonica rice to use the materials with low enzyme activity at the early stage of grain filling or high enzyme activity at the late stage as parents.

Moderate drought alleviates the damage to grain quality at high temperatures by improving the starch synthesis of inferior grains in japonica rice

In agricultural production,temperature and moisture are important factors affecting grain yield and quality.Although moderate drought at the grain-filling stage can effectively alleviate the damage caused by high temperature,the specific regulatory mechanism driving the effect of moderate drought at the high temperature on starch synthesis is still unclear.To explore the effects and mechanisms of high temperature and moderate drought on rice starch synthesis at the grainfilling stage,the activities of enzymes and expression levels of the genes involved in starch synthesis under four different treatments involving high temperature and/or water stress(CK,HT,WS,and HT+WS)were investigated in this study.The starch synthesis of a japonica inbred rice was measured under the four treatments during the grain filling.The results show that the effects of high temperature and moderate drought on grain filling mainly occur in the inferior grains of rice.Through the regulation of enzymes involved in starch synthesis and the expression levels of their main genes,the synthesis of rice starch can be affected.Therefore,the high temperature and moderate drought were antagonistic,and moderate drought can alleviate the damage to grain quality at a high temperature by improving the starch synthesis of inferior grains in japonica rice.This study provides a basis for stress-resistance cultivation and breeding strategies of rice with high temperature tolerance.

Diurnal Changes in the Transcription Profiles of Genes Encoding Starch Synthesis-related Enzymes in Wheat Grains under Field Conditions

[Objective] During the filling stage of plant growth and development, storage starch is diurnally synthesized and accumulated in the grains from cereal crops, but the underlying molecular mechanism is unclear. [Method] In this study, grains from the bread wheat cultivar Zhoumai 18 grown in fields were harvested at 15 d after anthesis, and quantitative real-time reverse transcription polymerase chain reaction(qPCR) was used to measure the transcriptional levels of 26 genes encoding starch synthesis-related enzymes at 2 h intervals throughout a diurnal cycle. [Result] Our findings indicated that storage starch was persistently synthesized in wheat grains throughout a 24 h period. The diurnal patterns of the transcriptional levels of 26 genes in wheat grains were classified into two groups. The 13 genes in Group 1 were temporally and highly expressed in wheat grains,and their encoded proteins could play crucial roles in starch synthesis. The other 13 genes in Group 2 were characterized by low or no transcription in wheat grains throughout a diurnal cycle, suggesting their function in the synthesis or degradation of transitory starches in wheat grains. [Conclusion] These results provide information on the molecular mechanism of storage starch synthesis in higher plants.

Genetic Evaluation of Starch Synthesis-Related Genes and Starch Quality Traits in Special Rice Resources

The genetic diversity of 36 rice landraces and 43 breeding materials in the upper reaches of the Yangtze River in China was studied by intragenic molecular markers of 26 starch synthesis-related loci.And research on quality traits such as the amylose content(AC),gel consistency(GC)and alkali spreading value(ASV)to analyze genetic differences in quality traits.The results showed that the number of alleles,average gene diversity and polymorphism information content values of landraces were higher than those of breeding materials.The genetic similarity coefficient(GS)of 79 rice materials ranged from 0.392 to 1,with an average of 0.757.There were significant variations in the quality traits of rice landraces and breeding materials,and the high-quality compliance rates were low,only 6.3%of the varieties have an amylose content that reached grade 1.The results of cluster analysis and population structure analysis are generally consistent;that is,the two resource types are closely related and cannot be clustered independently.This study can provide a basis for genetic improvement of rice starch quality.Make full use of the quality genetic diversity of landraces in modern breeding work,further broaden the genetic base of rice and improve rice quality.

TabHLH95-TaNF-YB1 module promotes grain starch synthesis in bread wheat

Starch is the most abundant substance in wheat(Triticum aestivum L.)endosperm and provides the major carbohydrate energy for human daily life.Starch synthesis-related(SSR)genes are believed to be spatiotemporally specific,but their transcriptional regulation remains unclear in wheat.Here,we investigate the role of the basic helix-loop-helix(bHLH)transcription factor TabHLH95 in starch synthesis.TabHLH95 is preferentially expressed in the developing grains in wheat and encodes a nucleus localized protein without autoactivation activity.The Tabhlh95 knockout mutants display smaller grain size and less starch content than wild type,whereas overexpression of TabHLH95 enhances starch accumulation and significantly improves thousand grain weight.Transcriptome analysis reveals that the expression of multiple SSR genes is significantly reduced in the Tabhlh95 mutants.TabHLH95 binds to the promoters of ADP-glucose pyrophosphorylase large subunit 1(AGPL1-1D/-1B),AGPL2-5D,and isoamylase(ISA1-7D)and enhances their transcription.Intriguingly,TabHLH95 interacts with the nuclear factor Y(NF-Y)family transcription factor TaNF-YB1,thereby synergistically regulating starch synthesis.These results suggest that the TabHLH95-TaNF-YB1 complex positively modulates starch synthesis and grain weight by regulating the expression of a subset of SSR genes,thus providing a good potential approach for genetic improvement of grain productivity in wheat.

GRAIN INCOMPLETE FILLING 2 regulates grain filling and starch synthesis during rice caryopsis development

Rice grain filling determines grain weight, final yield and grain quality. Here, a rice defective grain filling mutant, gif2, was identified. Grains ofgif2 showed a slower filling rate and a significant lower final grain weight and yield compared to wild-type. The starch content in gilt2 was noticeably decreased and its physicochemical properties were also altered. Moreover, gif2 endosperm cells showed obvious defects in compound granule formation. Posi- tional cloning identified GIF2 to encode an ADP-glucose pyrophosphorylase （AGP） large subunit, AGPL2; consequently, AGP enzyme activity in gif2 endosperms was remarkably decreased. GIF2 is mainly expressed in developing grains and the coded protein localizes in the cytosol. Yeast two hybrid assay showed that GIF2 interacted with AGP small subunits OsAGPS% OsAGPS2a and OsAGPS2b. Transcript levels for granule-bound starch synthase, starch synthase, starch branching enzyme and starch debranching enzyme were distinctly elevated in gif2 grains. In addition, the level of nucleotide diversity of the GIF2 locus was extremely low in both cultivated and wild rice. All of these results suggest that GIF2 plays important roles in the regulation of grain filling and starch biosynthesis during caryopsis development, and that it has been preserved during selection throughout domestication of modern rice.

Effect of Temperature on Rice Starch Biosynthesis Metabolism at Grain-Filling Stage of Early Indica Rice

The sucrose content, starch content and the ratio of amylose to total starch and the activities of six key enzymes, sucrose synthase(SS) , soluble starch synthesis enzyme(SSS) , ADPG pyrophosphorylase (ADPG-Ppase) , granule-boundstarch synthase (GBSS), starch branching enzyme (SBE) and debranching enzyme (DBE) , which involved in starch synthesis metabolism of developing rice grains and effect of temperature on their activities were analyzed by using two early indica varieties Zhefu49 and Jiazao935 in phyto-trons, the daily average temperature was 22 and 32℃, respectively. Results showed that the sucrose content, the starch content, and the activities of enzymes such as SS, ADPG-Ppase, SSS, SBE, and DBE were generally higher under the high temperature treatment (32℃)at the beginning stage as compared with that under low temperature treatment (22℃). However, at the middle and late stages, there were great differences in the change trend of some enzyme activities, and the association with the sucrose content and starch content was very complicated. It could be found that the activities of SS and SSS under high temperature were always lower than that under low temperature, which was closely related to the variation of the sucrose content and starch-accumulating rate. Moreover, compared with ADPG-Ppase, the SS and SSS activities were more sensitive to temperature, indicating that SS and SSS were controlled by enzyme through affecting starch accumulating rate. Difference of the amylose/total starch ratio in developing grains between 32 and 22℃was significant and the lower amylose/total starch ratio was always lower in 32℃, which was closely related to the lower activity level of GBSS. Therefore, it could be concluded that effect of temperature on amylose /total starch was more attributable to GBSS rather than to SS, SSS, ADPG-Ppase, SBE and DBE.

Molecular cloning,characterization and expression analysis of three key starch synthesis-related genes from the bulb of a rare lily germplasm,Lilium brownii var.giganteum

Starch is the predominant compound in bulb scales,and previous studies have shown that bulblet development is closely associated with starch enrichment.However,how starch synthesis affects bulbification at the molecular level is unclear.In this study,we demonstrate that Lilium brownii var.giganteum,a wild lily with a giant bulb in nature,and L.brownii,the native species,have different starch levels and characteristics according to cytological and ultra-structural observations.We cloned the complete sequence of three key gene-encoding enzymes(LbgAGPS,LbgGBSS,and LbgSSⅢ)during starch synthesis by rapid amplification of 5’and 3’complementary DNA(cDNA)ends(RACE)technology.Bioinformatics analysis revealed that the proteins deduced by these genes contain the canonical conserved domains.Constructed phylogenetic trees confirmed the evolutionary relationships with proteins from other species,including monocotyledons and dicotyledons.The transcript levels of various tissues and time course samples obtained during bulblet development uncovered relatively high expression levels in bulblets and gradual increase expression accompanying bulblet growth.Moreover,a set of single nucleotide polymorphisms(SNPs)was discovered in the AGPS genes of four lily genotypes,and a purifying selection fashion was predicted according to the non-synonymous/synonymous(Ka/Ks)values.Taken together,our results suggested that key starch-synthesizing genes might play important roles in bulblet development and lead to distinctive phenotypes in bulblet size.

Effects of Early- and Late-Sowing on Starch Accumulation and Associated Enzyme Activities During Grain Filling Stage in Rice

The environmental temperature occurring during the grain filling stage is an important factoraffecting starch synthesis and accumulation in rice. We investigated starch accumulation, amylaseactivity and starch granule size distribution in two low-amylose japonica rice varieties, Nanjing 9108 andFujing 1606, grown in the field at different filling temperatures by manipulating sowing date. The two ricevarieties exhibited similar performances between two sowing dates. Total starch, amylose andamylopectin contents were lower at the early-filling stage of T1 treatment (Early-sowing) compared withthose at the same stage in T2 treatment (Late-sowing). In contrast, at the late-filling stage, when fieldtemperatures were generally decreasing, total starch and amylopectin contents in T1 were highercompared to those in T2. The ideal temperature for strong activity of ADP-glucose pyrophosphorylaseand soluble starch synthase was about 22℃. A higher temperature from the heading to maturity stagesin T1 increased the activities of starch branching enzyme and suppressed the activities of granule boundstarch synthetase and starch debranching enzyme. We found that rice produced larger-sized starchgranules under the T1 treatment. These results suggested that due to the early-sowing date, the hightemperature (30℃) occurring at the early-filling stage hindered starch synthesis and accumulation,however, the lower temperatures (22 ℃) at the late-filling stage allowed starch synthesis and accumulationto return to normal levels.

A genetic diversity assessment of starch quality traits in rice landraces from the Taihu basin,China

There are nearly 1 000 rice landrace varieties in the Taihu basin, China. To assess the genetic diversity of the rice, 24 intragenic molecular markers（representing 17 starch synthesis-related genes） were investigated in 115 Taihu basin rice landraces and 87 improved cultivars simultaneously. The results show that the average genetic diversity and polymorphism information content values of the landraces were higher than those of improved cultivars. In total, 41 and 39 allele combinations（of the 17 genes） were derived from the landraces and improved cultivars, respectively; only two identical allele combinations were found bet ween the two rice variety sources. Cluster analysis, based on the molecular markers, revealed that the rice varieties could be subdivided into five groups and, within these, the japonica improved rice and japonica landrace rice varieties were in two separate groups. According to the quality reference criteria to classify the rice into grades, some of the landraces were found to perform we ll, in terms of starch quality. For example, according to NY /T595-2002 criteria from the Ministry of Agriculture of China, 25 and 33 landraces reached grade 1, in terms of their apparent amylose content and gel consistency. Th e varieties that had outstanding quality could be used as breeding materials for rice quality breeding programs in the future. Our study is useful for future applications, such as genetic diversity studies, the protection of rice variety and improvment of rice quality in breeding programs.

Modulation of starch synthesis in Arabidopsis via phytochrome B-mediated light signal

Starch is a major storage carbohydrate in plants and is critical in crop yield and quality.Starch synthesis is intricately regulated by internal metabolic processes and external environmental cues;however,the precise molecular mechanisms governing this process remain largely unknown.In this study,we revealed that high red to far-red(high R:FR)light significantly induces the synthesis of leaf starch and the expression of synthesis-related genes,whereas low R:FR light suppress these processes.Arabidopsis phytochrome B(phyB),the primary R and FR photoreceptor,was identified as a critical positive regulator in this process.Downstream of phyB,basic leucine zipper transcription factor ELONGATED HYPOCOTYL5(HY5)was found to enhance starch synthesis,whereas the basic helix-loop-helix transcription factors PHYTOCHROME INTERACTING FACTORs(PIF3,PIF4,and PIF5)inhibit starch synthesis in Arabidopsis leaves.Notably,HY5 and PIFs directly compete for binding to a shared G-box cis-element in the promoter region of genes encoding starch synthases GBSS,SS3,and SS4,which leads to antagonistic regulation of their expression and,consequently,starch synthesis.Our findings highlight the vital role of phyB in enhancing starch synthesis by stabilizing HY5 and facilitating PIFs degradation under high R:FR light conditions.Conversely,under low R:FR light,PIFs predominantly inhibit starch synthesis.This study provides insight into the physiological and molecular functions of phyB and its downstream transcription factors HY5 and PIFs in starch synthesis regulation,shedding light on the regulatory mechanism by which plants synchronize dynamic light signals with metabolic cues to module starch synthesis.

Photosynthesis,Carbohydrate Storage and Remobilization During Grain Filling as Affected by Sulphur Application in Winter Wheat

Photosynthesis and carbohydrate storage and remobilization was investigated during grain filling of winter wheat (Triticumaestivum L., cv. Lumai 22) in sulphur application experiments where the available sulphur (S) content in the soil of 0-20 cmsoil layer was 5.84 mg kg-1. Two levels of S were applied as S0 (0 kg S ha-1) and S1 (67.5 kg S ha-1). The results showed thatnet photosynthetic rate of flag leaf of S1 treatment was significantly higher than S0 treatment, and it increased graduallyfrom anthesis to 35 DAA. Sucrose-phosphate synthase (SPS) activity and sucrose content of S1 treatment were significantlyhigher than those of S0 treatment. The contents of total soluble sugar, sucrose, fructose, glucose, DP3 and DP ≥ 4fructan in stem and sheath of S1 treatment were significantly higher than those of S0 treatment also. The amount of totalsoluble sugar and fructans remobilization from stem and sheath and the starch accumulating rate in grain of S1 treatmentwas significantly higher than those of S0 treatment. It is suggested that sulphur application increase photosynthateremobilization from stem and sheath to grain at later filling stage.

The 218th amino acid change of Ser to Ala in TaAGPS-7A increases enzyme activity and grain weight in bread wheat

ADP-glucose pyrophosphorylase(AGPase)influences cereal productivity.There are few reports on the function of cytosolic AGPase small subunit in bread wheat(TaAGPS).In the present study,TaAGPS was preferentially expressed in developing endosperm during grain-filling stages in bread wheat.TaAGPS allelic variations were characterized in 143 wheat accessions by PacBio RS II sequencing.Two haplotypes(TaAGPS-7A-TG and TaAGPS-7A-CT)of TaAGPS-7A were identified and corresponding functional markers were developed,whereas no variants of TaAGPS-7B and TaAGPS-7D were detected.TaAGPS-7A was associated with thousand-kernel weight(TKW)by haplotype–trait association analysis in two populations.Near-isogenic lines(NILs)with TaAGPS-7A-TG showed higher TKW and total kernel starch content than those with TaAGPS-7A-CT,owing to the higher AGPase activity of TaAGPS-7A-TG than TaAGPS-7A-CT both in vitro and in vivo.Overexpression of TaAGPS-7A-TG in bread wheat doubled the transcription levels of TaAGPS and increased AGPase activity by 55.7%,resulting in a 3.0-g higher TKW than in the wild type(WT).Knockdown of TaAGPS led to reduced expression of TaAGPS,AGPase activity,and TKW than in the WT.Thus,owing to the 218th amino acid change of Ser to Ala in TaAGPS-7A,the favorable haplotype TaAGPS-7A-TG showed higher AGPase activity,resulting in higher kernel starch content and grain weight.This finding could be applied to increasing starch content and grain weight in bread wheat.

FGW1, a protein containing DUF630 and DUF632 domains, regulates grain size and filling in Oryza sativa L.

Grain filling influences grain size and quality in cereal crops. The molecular mechanisms that regulate grain endosperm development remain elusive. In this study, we characterized a filling-defective and grain width mutant, fgw1, whose mutation increased rice seed width mainly via cell division and expansion in grains. Sucrose contents were higher but starch contents lower in the fgw1 mutant during the grainfilling stage, resulting in inferior endosperm of opaque, white appearance with loosely packed starch granules. Map-based cloning revealed that FGW1 encoded a protein containing DUF630/DUF632domains, localized in the plasma membrane with preferential expression in the panicle. RNA interference in FGW1 resulted in increased grain width and weight, whereas overexpression of FGW1 led to slightly narrower kernels and better grain filling. In a yeast two-hybrid assay, FGW1 interacted directly with the 14–3–3 protein GF14f, bimolecular fluorescence complementation verified that the site of interaction was the membrane, and the mutated FGW1 protein failed to interact with GF14f. The expression of GF14f was down-regulated in fgw1, and the activities of AGPase, StSase, and SuSase in the endosperm of fgw1increased similarly to those of a reported GF14f-RNAi. Transcriptome analysis indicated that FGW1 also regulates cellular processes and carbohydrate metabolism. Thus, FGW1 regulated grain formation via the GF14f pathway.

Effects of nitrogen fertilizer and chemical regulation on spring maize lodging characteristics, grain filling and yield formation under high planting density in Heilongjiang Province, China

Now,lodging is a major constraint factor contributing to yield loss of maize (Zea mays L.) under high planting density.Chemical regulation and nitrogen fertilizer could effectively coordinate the relationship between stem lodging and maize yield,which significantly reduce lodging and improve the grain yield.The purpose of this study was to explore the effects of chemical regulation and different nitrogen application rates on lodging characteristics,grain filling and yield of maize under high density.For this,we established a field study during 2017 and 2018 growing seasons,with three nitrogen levels of N100 (100 kg ha^(–1)),N200 (200 kg ha^(–1)) and N300 (300 kg ha^(–1)) at high planting density (90 000 plants ha^(–1)),and applied plant growth regulator (Yuhuangjin,the mixture of 3% DTA-6 and 27% ethephon) at the 7th leaf.The results showed that chemical control increased the activities of phenylalanine ammonia-lyase (PAL),tyrosine ammonia-lyase (TAL),4-coumarate:Co A ligase (4CL),and cinnamyl alcohol dehydrogenase (CAD),and increased the lignin,cellulose and hemicellulose contents at the bottom of the 3rd internode,which significantly reduced the lodging percentage.The lignin-related enzyme activities,lignin,cellulose and hemicellulose contents decreased with the increase of nitrogen fertilizer,which significantly increased the lodging percentage.The 200 kg ha^(–1) nitrogen application and chemical control increased the number,diameter,angle,volume,and dry weight of brace roots.The 200 kg ha^(–1) nitrogen application and chemical control significantly increased the activities of ADP-glucose pyrophosphorylase (AGPase),soluble starch synthase (SSS) and starch branching enzyme(SBE),which promoted the starch accumulation in grains.Additional,improved the maximum grain filling rate (V_(max)) and mean grain filling rate (V_(m)),which promoted the grain filling process,significantly increased grain weight and grain number per ear,thus increased the final yield.

新型复合白乳胶

研究了以聚乙烯醇缩甲醛，氧化淀粉为主要粘接基料，以硬脂酸盐为乳化剂，利用瞬间成皂乳化法生产一种新型复合白乳胶的工艺条件。