Characterization using Raman microspectroscopy of arabinoxylans in the walls of different cell types during the development of wheat endosperm

The time course and pattern of arabinoxylan deposition in the wheat (Triticum aestivum) endosperm during grain development were studied using Raman spectroscopy. The presence of arabinoxylans (AX) is detected at the beginning of grain filling. At this stage, AX appear more substituted than at the later stages. Feruloylation of AX increases during the grain-filling stage, especially in the case of the aleurone layer. Whatever the stage of grain development, four populations of cells could be defined according to Raman arabinoxylan signatures. In the walls of the aleurone cells, AX appeared to be little substituted and highly esterified with phenolic acids. In the walls of prismatic cells, AX were found to be highly substituted and poorly esterified. Apart from aleurone and prismatic cells, the substitution degree of AX in endosperm was in the same range. Cells in the crease region were distinguished from cells in the starchy endosperm by their lower amount of esterified phenolic compounds.     

Structure, chemical composition, and xylanase degradation of external layers isolated from developing wheat grain

The external layers of wheat grain were investigated during maturation with respect to chemical and structural features and xylanase degradability. Cytochemical changes were observed in the isolated peripheral tissues of the wheat grain at four defined stages following anthesis. Marked chemical changes were highlighted at 11 days after anthesis, for which protein and lipid contents varied weakly. The profile of esterified ferulic acid showed large variation in the maturing peripheral layers of grain in contrast to the deposition of ferulate dimers, p-coumaric and sinapic acids. Lignin was monitored at the latest stages of ripening, which corresponds to the cessation of reserve accumulation in the grain. Arabinoxylans (AX) reached a maximum at 20 days and did not display any significant change in arabinosyl substitution proportion until ripeness. When submitted to xylanase, all outer layers were similarly altered in the proportion of soluble AX except for the peripheral tissues of the 11-day-aged wheat grain that had very little AX. Aleurone and nucellar layers were mostly degraded, whereas pericarp stayed intact at all stages of maturation. This degradation pattern was connected with the preferential immunolocalization of xylanase in aleurone and nucellar layers irrespective of the developmental stages. Further chemical examination of the enzyme-digested peripheral tissues of the grain supports the facts that ferulic ester is not a limiting factor in enzyme efficiency. Arabinose branching, ferulic dimers, and ether-linked monomers that are deposited early in the external layers would have more relevance to the in situ degradability of AX.     

Classification of wheat varieties based on structural features of arabinoxylans as revealed by endoxylanase treatment of flour and grain

Arabinoxylans (AX) are cell wall polysaccharides of complex structure involved in many aspects of wheat flour end uses. The study of the variations of AX structure can lead to the identification of genes involved in their biosynthesis, and thus in the control of the various aspects of grain quality related to their presence. A method is proposed to identify AX variations directly in whole grain by enzymatic degradation. An endoxylanase from Trichoderma viride was used to extract AX from a collection of 20 wheat cultivars (Triticum aestivum L.). Enzymatic degradation products were analyzed by HPAEC and multivariate analysis techniques (principal component analysis, canonical correlation analysis, and cluster analysis) were applied to analyze chromatographic data. The method evidenced variations in the proportion of mono- and disubstitution of the xylan backbone by arabinose side chains, allowing classification of the different varieties according to the structural features of AX. A similar classification was obtained starting from flour or whole grain, indicating that the method was specific of AX from endosperm tissues. In conclusion, the method combining endoxylanase treatment of wheat grain and the analysis of degradation products, e.g., enzymatic fingerprinting, can be applied to collections of wheat cultivars, and possibly other cereals in order to establish quantitative trait loci related to the biosynthesis of AX.     

Inactive fluorescently labeled xylanase as a novel probe for microscopic analysis of arabinoxylan containing cereal cell walls

A new technique to visualize cereal cell walls by fluorescence microscopy was developed. The novel staining technique is based on an inactive fluorescently labeled xylanase binding to arabinoxylan (AX), an important polysaccharide in grain cell walls in terms of the technological and physiological functionalities of grain. The xylanase probe could stain AX in the seed coat, nucellar epidermis, aleurone layer, and starchy endosperm, but not the highly substituted AX of the pericarp layer. The advantage of this new staining technique over the existing immunolabeling techniques is that the staining procedure is clearly faster and less laborious, and uses a smaller probe that can easily be produced by marking a well characterized enzyme with a fluorescent label. In the future, the here proposed technology can be used to develop probes having specificity also for cell wall components other than AX and thus to study plant cell walls further through fluorescence microscopy.     

Amyloplast Formation and Starch Granule Development in Hard Red Winter Wheat

Plastids in the coenocytic endosperm of young wheat caryopses were mostly in the form of pleomorphic proplastids with a few of the plastids containing small starch granules. Following cellularization of the coenocytic cytoplasm, the outer one or two endosperm cell layers became meristematic and continued to divide until about 14 days after flowering (DAF). During the first week of endosperm development, newly divided cells had plastids that were pleomorphic in shape, while subaleurone cells interior to the meristematic region contained amyloplasts that contained a single‐size class of starch granules (incipient A‐type starch granules). The pleomorphic plastids exhibited tubular protrusions that extended a considerable distance through the cytoplasm. Amyloplasts in cells interior to the meristematic region did not exhibit protrusions. Both subaleurone and central endosperm cells had amyloplasts that exhibited protrusions at 10–12 DAF, and some of the protrusions contained small starch granules (incipient B‐type starch granules). Protrusions were not observed in endosperm amyloplasts at 14 DAF. Two sizes of starch, large A‐type and smaller B‐type granules were present within the cells, however. Amyloplast protrusions were numerous again at 17 DAF in both subaleurone and central endosperm cells; at 21 DAF, a third size class of small C‐type starch granules was observed in the cytoplasm. Amyloplasts in the endosperm of wheat apparently divided and increased in number through protrusions because binary fission typical of plastid division was never observed. Protrusions were observed in the coenocytic cytoplasm, in dividing cells, in subaleurone and central endosperm cells at 10–12 DAF, and in subaleurone and central endosperm cells at 17 DAF. The results suggest that there are three sizes of starch granules produced at specific times during wheat endosperm development.     

FT-IR investigation of cell wall polysaccharides from cereal grains. Arabinoxylan infrared assignment

The FT-IR fingerprint of wheat endosperm arabinoxylan (AX) was investigated using a set of polysaccharides exhibiting variation of their degree of substitution and xylo-oligosaccharides comprising xylose units mono- or disubstituted by arabinose residues. Substitution of the xylose backbone by arabinose side units was more particularly studied in the 1000-800 cm(-1) spectral region, by taking advantage of second-derivative enhancement. The 920-1020 cm(-1) spectral region revealed two absorption bands at 984 and 958 cm(-1), the intensities of which varied according to the degree of substitution. Whereas the intensity of the band at 958 cm(-1) increased with the degree of substitution, that at 984 cm(-1) decreased. The second-derivative spectral data of xylo-oligosaccharides indicated that these changes could be attributed to substitution of the xylan backbone by arabinose residues, and the band at 958 cm(-1) was ascribed to the presence of disubstituted xylose residues. Principal component analysis of FT-IR spectra of model mixtures of AX, beta-glucans, and arabinogalactans suggested that it is possible to evaluate the relative proportions of the polymers and degree of substitution of AX in complex mixtures such as the cell wall of cereal grains.     

小麦中功能性多糖－阿拉伯木聚糖研究进展

阿拉伯木聚糖（AX）是小麦细胞壁的主要结构多糖,具有高分子量、高粘度、氧化胶凝等物化特性。AX对于小麦及其面制品的加工品质具有重要影响,同时它还具有显著的降血脂、减肥、免疫调节等生理活性。小麦品种间阿拉伯木聚糖存在一定的遗传变异规律。本文回顾了近年来国内外在小麦阿拉伯木聚糖研究方面取得的成果,将为更好地利用这一功能性多糖提供思路。     

追氮时期对不同粒色类型小麦产量和品质的影响

为了研究追施氮肥时期对不同粒色类型小麦产量和品质的影响,以白粒小麦、黑粒小麦、绿粒小麦各两个品种为材料在大田里进行不同追氮时期的试验。结果表明,春5叶追氮在提高小麦的子粒蛋白及组分含量方面要优于春2叶追氮。绿粒小麦、黑粒小麦的子粒蛋白质含量显著高于本试验所选的白粒小麦,且通过追氮时期的后移可以拉大这种差距。追氮时期对加工品质的影响不存在品种差异,各品种春5叶追氮处理的结果均高于春2叶。追氮时期对不同粒色类型小麦的形成时间和稳定时间的影响较小,但它会影响黑粒小麦的沉降值和湿面筋含量,所以氮肥运筹对黑粒小麦加工品质的改善有一定意义。和春2叶追氮相比,春5叶追氮更有利于提高小麦的产量,绿粒小麦和白粒小麦的产量及相关指标受追氮时期的影响相对较大,黑粒小麦受追氮时期的影响较小。     

Eine verbesserte Methode zur Bestimmung der Anzahl von Endospermzellen in Weizenkörnern

An improved method for the determination of the number of endosperm cells in wheat grains A method is described, which allows a clear and quantitative determination of endosperm cells in wheat grains even during the late stages of grain filling. After treatment with pectinase the tissue of the endosperm disintegrates in single cells, in the same step the starch in the endosperm cells is dissolved. The nuclei of the endosperm cells are stained with hematoxylin, drawn by vacuum on to a millipore filter, and counted in the still recognizable cell structures under a microscope. This is advantageous for exact counting of all the endosperm cells.     

Spectroscopic analysis of diversity of Arabinoxylan structures in endosperm cell walls of wheat cultivars (Triticum aestivum) in the HEALTHGRAIN diversity collection

Fifty bread wheat (Triticum aestivum L.) cultivars were selected from the HEALTHGRAIN germplasm collection based on variation in their contents of total and water-extractable arabinoxylan. FT-IR spectroscopic mapping of thin transverse sections of grain showed variation in cell wall arabinoxylan composition between the cultivars, from consisting almost entirely of low-substituted arabinoxylan (e.g., T.aestivum 'Claire') to almost entirely of highly substituted arabinoxylan (e.g., T.aestivum 'Manital') and a mixture of the two forms (e.g., T.aestivum 'Hereward'). Complementary data were obtained using endoxylanase digestion of flour followed by HP-AEC analysis of the arabinoxylan oligosaccharides. This allowed the selection of six cultivars for more detailed analysis using FT-IR and (1)H NMR spectroscopy to determine the proportions of mono-, di-, and unsubstituted xylose residues. The results of the two analyses were consistent, showing that variation in the composition and structure of the endosperm cell wall arabinoxylan is present between bread wheat cultivars. The heterogeneity and spatial distribution of the arabinoxylan in endosperm cell walls may be exploited in wheat processing as it may allow the production of mill streams enriched in various arabinoxylan fractions which have beneficial effects on health.     

小麦灌浆过程籽粒水分变化的核磁共振检测

花期至成熟期是小麦产量形成的关键时期,在这一时期麦穗的水分状态随着干物质的积累而呈现出独特的变化特征。为了揭示活体冬小麦灌浆过程的水分变化规律,利用核磁共振技术的无损检测特性,结合核磁共振质子密度加权成像和核磁共振T2弛豫谱分析,对小麦麦穗进行了连续活体检测。核磁共振质子密度加权成像结果表明,灌浆前期籽粒的水分不断增加,至花后15 d籽粒的水分含量达到最大值,此后小麦籽粒的水分逐渐减少。在此过程中,灌浆物质在籽粒中积累的顺序是由外向内、自上而下的。经核磁共振T2弛豫谱分析,麦穗中的水分可分为结合水、半结合水和自由水三种相态。从籽粒形成至完熟期麦穗不同相态的水分都表现为先增大后减小的特点,但涨落步调不尽相同,其中结合水含量的增长期最长,至蜡熟期结束时(花后33 d)才达到最大值。籽粒形成后麦穗总水分含量维持在较高水平,即使在籽粒干质量快增期(花后15 d至花后27 d),籽粒中干物质的迅速积累也并未导致水分含量的明显减小,单穗的总水分含量与最大水分含量相比仅仅减少了十分之一。花后30 d之后,随着颖片及穗轴逐渐变黄衰老和籽粒的脱水成熟,麦穗水分含量才急剧减小。小麦灌浆中期麦穗维持较高水分含量,说明水分在同化物积累过程中的重要作用。除了灌浆中期较高的水分含量,蜡熟期的快速脱水亦有利于营养物质的贮存并减少呼吸消耗,对于小麦产量的形成和稳定亦具有重要意义。     

Einfluß exogen veränderter „source-sink”︁-Beziehungen auf die Anzahl der Endospermzellen und die Kornentwicklung bei Sommerweizen

Influence of an exogenously changed source-sink relationship on the number of endosperm cells and grain development in spring wheat In 2 years pot experiments with spring wheat the source-sink ratio was changed by shading the plants at different times after anthesis, by removal of flag leaf blades, and by phytohormone treatment of the ear. The effect of the different treatments was recorded by determining the number of endosperm cells per grain, the single grain weight and the grain yield. In grains of normally illuminated plants the maximum number of endosperm cells was reached 2 to 3 weeks after anthesis. The storage of assimilates within these cells depends on the intensity of illumination during the entire grain filling period. Shading the plants between anthesis and maturity led to a 23 to 34% decrease in grain yield, but only to a 7 to 16% decrease in the number of endosperm cells. The same drop in the endosperm cell number was observed in plants shaded for only 15 days from the start of anthesis. A subsequent period of normal illumination till maturity led to a marked increase in the single grain weight. No decrease in the endosperm cell number was seen in plants shaded from the 15^th day after anthesis till maturity. There was, however, a 12–13% reduction in the single grain weight and grain yield in these plants as compared with the control. Removal of the flag leaf at anthesis reduced the number of endosperm cells by 6 to 11%, the single grain weight by 10 to 29% and the grain yield by 15 to 25%. CCC and Ancymidol treated plants in the shading trials showed the same decrease in the endosperm cell number but a more pronounced reduction in the single grain weight compared with control plants. Their reactions to the various shading trials followed the same general pattern as the control plants. The results of the shading experiments confirm that the endosperm cell number is not the only determinating factor for the single grain weight. The application of kinetin and abscisic acid to the ear had no effect on the number of endosperm cells and single grain weight. Abscisic acid, however, reduced the number of graines per ear.     

REVIEW: Rye Arabinoxylans: Molecular Structure,Physicochemical Properties and Physiological Effects in the Gastrointestinal Tract

Arabinoxylans (AX) are the main dietary fiber (DF) polysaccharides in rye where they represent ≈55% of the total polysaccharides. Rye AX consist of a backbone of (1→4)‐β‐d ‐xylopyranosyl residues (X) mainly substituted with α‐l ‐arabinofuranosyl residues (A) to varying degrees at the O‐2 position, the O‐3 position, or both. The A/X ratio of total AX is 0.49–0.82 and extractable AX ratio is 0.34–0.85 in different studies. AX also contain small amounts of ferulate residues bound to arabinose as esters at its O‐5 position. The weight average molecular weight varies from 40,000 to 900,000 with an average of ≈200,000. AX influence physiology in different segments of the gastrointestinal tract. The complex molecular structure of rye AX makes them resistant against microbial modification in the small intestine; consequently, rye AX have a much higher influence on the viscosity in the small intestinal digesta than does β‐glucan from oats and barley. In spite of that, it has not been possible in studies with AX‐rich foods such as bread to demonstrate a significant effect on the postprandial glucose response, however, a significantly reduced insulin response has been seen. Nevertheless, addition of 6 g and 12 g of AX‐rich wheat fiber to a breakfast meal has significantly lowered postprandial glucose and insulin response. Studies with hypercholesterolemic pigs fed rye buns rich in AX have resulted in dramatic reductions in plasma total and LDL cholesterol, whereas a gender difference was seen in studies on the effect of AX on plasma lipids in humans. Only certain species of bacteria from the human gut produce the enzymes needed for the degradation of AX. Nevertheless, wheat AX stimulate prebiotic bacteria presumably brought about by cross feeding of lactobacilli and bifidobacteria with degradation products from versatile carbohydrate‐degrading bacteria. Soluble AX are readily fermented in the large intestine, the majority is broken down between the ileum and the cecum. AX, characterized by a low degree of substitution and virtually no doubly substituted xylose, are slowly degraded at more distal locations. The remaining AX, characterized by a high degree of substitution, are not degraded at all. Although the fermentation pattern of AX may vary in different experimental models, in vitro fermentation studies and in vivo intervention studies with animals and humans point to AX as substrates that enhance the formation of butyrate in the large intestine.     

Association and structural diversity of hemicelluloses in the cell walls of rye outer layers: comparison between two ryes with opposite breadmaking quality

Looking for potential quality indicators, which could be used in early selection of breeding materials, the structural features of cell wall arabinoxylans (AX) from outer layers of the grain (pooled shorts and bran fractions) were studied in two ryes with diverse breadmaking quality. The successive alkaline extraction of water-unextractable material with saturated Ba(OH)2, followed by water and 1 and 4 M NaOH, resulted in four purified fractions, Ba, BaH, 1Na, and 4Na, respectively, that became water soluble after their isolation. The AX present in these fractions constituted approximately 43, 12, 14, and 4% of their total amount recovered. Moreover, two xylan-enriched fractions, 1Na.P and 4Na.P (arabinose-to-xylose ratios, Ara/Xyl, of 0.07 and 0.19, respectively), were self-precipitated from both NaOH-extractable fractions. Polysaccharides of these fractions, containing mainly xylose, represented approximately 16 and 1% of AX recovered. In the BaH and 1Na, AX coexisted with beta-glucans, which predominated in the former protein-free fraction. On the contrary, hemicelluloses in the 1Na fraction were associated with protein as well. Further fractionation of the water-soluble materials by ammonium sulfate revealed that the parent AX populations in the Ba, BaH, and 1Na were composed of 3-4 subfractions with different degrees of substitution (Ara/Xyl of approximately 0.4, 0.8, and 1.1), whereas 4Na was almost totally built of highly substituted AX (Ara/Xyl of 1.1). Despite a comparable proportion of un-, mono-, and disubstituted xylopyranosyl residues in the chain of Ba(OH)2-extractable AX isolated from both ryes, the 1H NMR and Fourier transform infrared demonstrated the marked differences in their spectral profiles, suggesting different substitution patterns of these dominating polysaccharides. The high molecular weight population present in the Ba fraction also differentiated well two ryes with opposite breadmaking quality.     

Wheat Arabinoxylan Structure Provides Insight into Function

Recent attention to dietary fiber in wheat (Triticum aestivum L.) has invigorated research in the nonstarch carbohydrate arabinoxylan (AX). AX molecules are composed of a linear xylose backbone with arabinose substitutions along the backbone. These arabinose substituents can also carry a ferulic acid moiety. AX molecules can be fractionated into two categories based on extraction properties that have a structural and conformational basis: water‐extractable (WEAX) and water‐unextractable (WUAX) molecules. The ferulic acid moieties also allow for oxidative cross‐linking between AX molecules or the tyrosine residues of proteins. The contents of total AX and WEAX molecules are primarily influenced by genetic differences; however, there is also evidence of environmental influence on content. There are several useful methods for quantifying AX molecules, providing varying levels of structural information as well as accuracy and precision. The high water‐absorption capacity of AX molecules results in a strong influence of AX on end‐use quality. Whereas WEAX molecules, in particular, tend to be detrimental for the quality of soft wheat products such as cookies, WEAX molecules are beneficial to the quality of hard wheat products such as bread. The role of WUAX molecules among the range of soft wheat products is as yet unclear; however, WUAX molecules tend to have a detrimental influence on bread. Because of the variable influence of AX structure on end‐use product functionality, closer examination of structure–function relationships may provide key insights into how to direct breeding efforts to maximize these relationships between AX molecules and other ingredients. Further investigation is necessary to obtain a more complete understanding of how the arabinose substitution levels and patterns affect end‐use quality and how the genetic basis of these traits can be resolved and manipulated for optimum end‐use quality.     

High temperature during grain fill alters the morphology of protein and starch deposits in the starchy endosperm cells of developing wheat (Triticum aestivum L.) grain

High temperature during grain fill reduces wheat yield and alters flour quality. Starchy endosperm cell morphology was investigated in wheat ( Triticum aestivum L. 'Butte 86') grain produced under a 24/17 or 37/28 °C day/night regimen imposed from anthesis to maturity to identify changes in cell structure related to the functional properties of flour. The duration of grain fill decreased substantially under the 37/28 °C regimen, but, like the 24/17 °C regimen, endosperm cells in the mature grain were packed with starch and protein. However, A-type starch granules increased in number, decreased in size, and exhibited pitting; B-type granules decreased in both number and size; and the protein matrix was proportionally greater in endosperm cells of grain produced under the 37/28 °C regimen. Such changes in starch granule number, size, and structure and in protein amount are known to contribute to variations in wheat flour quality.     

不同发育阶段谷蠹侵害对储藏小麦蛋白结构的影响

为探索谷蠹在不同生长发育阶段对储藏小麦蛋白结构的影响,该文以谷蠹种虫感染后的小麦为研究对象,对谷蠹不同发育阶段(卵期、幼虫期、蛹期、成虫期)侵害后小麦中麦谷蛋白大聚合体(glutenin macropolymer,GMP)、沉降值、面筋蛋白持水力、蛋白二级结构、巯基(-SH)、二硫键(-S-S-)及面筋显微结构进行测定与分析。结果表明:在谷蠹发育的4个阶段,GMP、沉降值、β转角总体呈增加趋势,-SH、β折叠比例变化与之相反;面筋蛋白持水力、-S-S-和α螺旋比例总体呈先降后升趋势,无规卷曲比例变化则与之相反。卵期谷蠹危害较小,只有β转角和面筋蛋白持水力有显著变化(P0.05);幼虫期和蛹期谷蠹危害严重,与相同试验条件下相应时期的无虫小麦对照样相比,GMP、无规卷曲和β转角比例及沉降值均显著增加(P0.05),面筋蛋白持水力、-SH、-S-S-、α螺旋和β折叠显著减少(P0.05)。面筋蛋白显微结构显示:随着谷蠹在小麦籽粒内部发育,面筋表面粗糙程度加重,微纤维状丝增多,结构疏松散乱,断裂严重,至成虫期时,面筋结构已无法识别,因此在实际储藏过程中不仅要关注成虫的数量,还应注意及时控制谷蠹的生长发育。     

Glutathione reductase in wheat grain. 1. Isolation and characterization

Durum wheat (Triticum durum, Desf.) endosperm of mature kernels contained a single form of glutathione reductase (GR); it appeared about the 18th day after anthesis while another isoform, present at the early stages of grain development, disappeared between the 20th and 30th days after flowering. The form that was present at grain maturity was isolated and characterized. It was composed of two monomers, each one having an apparent molecular mass of about 60 kDa. The K(m) values for NADPH and for GSSG were 3.7 and 9.1 microM, respectively, and the V(m) values for NADPH and for GSSG were 594 and 575 microkat.mg(-)(1) protein, respectively. The pH(i) of the enzyme was situated between pH 4.4 and 4.5. At a constant temperature of 25 degrees C, the optimum GR activity was found to be between pH 7.5 and 8.0. It was relatively resistant to high temperatures and was very resistant to very low temperatures.     

冬小麦小花发育及结实特性对叶面喷 6-BA 的响应

【目的】通过小花发育后期叶面喷细胞分裂素 6-苄氨基腺嘌呤 (6-BA)，探讨外源 6-BA 对小麦小花发育及结实成粒的调控效应，以期为增加小麦穗粒数、提高产量调控技术的研究提供参考。【方法】试验于 2012～2014 年在河南农业大学科教示范园区 (34°86′N, 113°59′E) 进行，以当前主推的半冬性品种豫麦 49-198 为供试材料，在拔节后 25 d 叶面喷清水 (对照 CK)、6-苄氨基腺嘌呤 (6-BA)，观察记载不同小穗位小花发育的动态变化及形态特征，按常规考种法记载不同小穗位 (基部、中部和顶部) 结实粒数、每小穗结实粒数和每小穗不同花位结实粒数。【结果】喷 6-BA 处理麦穗基部、中部、顶部小穗位的可孕小花数显著高于对照，其可孕小花的结实率分别提高 8.4%、15.1% 和 10.6%。进一步分析可知，喷 6-BA 处理抑制了基部和中部小穗小花的退化速率及可孕小花的败育速率，其中基部小穗位的小花退化速率降低 24.4%，可孕小花败育速率降低 73.0%；中部小穗位小花的退化速率降低 14.7%，可孕小花败育速率降低 76.0%；而且顶部小穗可孕小花的败育速率较对照降低 61.3%，最终使顶部小穗的结实率亦显著提高。喷 6-BA 处理还可显著促进不同小穗位的不同花位小花结实，尤其对促进第 3、4 花位弱势小花成粒效果显著。【结论】在冬小麦小花退化高峰之前 (拔节后 25 d)，采取叶面喷外源激素 6-BA，可明显降低基部小穗和中部小穗小花的退化速率与可孕小花的败育速率。另外，喷 6-BA 处理还可抑制顶部小穗可孕小花的败育速率，从而提高单穗的可孕花结实率，获得较高的最终结实粒数。     

Influence of Cultivar and Environment on Water‐Soluble and Water‐Insoluble Arabinoxylans in Soft Wheat

Arabinoxylans are hydrophilic nonstarch polysaccharides found in wheat grain as minor constituents. Arabinoxylans can associate with large amounts of water through hydrogen bonding and can form oxidative gels. These properties are important factors in end‐use quality of wheat. The objective of this study was to delineate the influence of wheat cultivar and growing environment on variation in water‐soluble (WS‐AX), waterinsoluble (WI‐AX), and total (TO‐AX) arabinoxylan contents of flour and whole grain meal. This study included seven spring and 20 winter soft white wheat cultivars grown in 10 and 12 environments, respectively (each evenly split over two crop years). Univariate analysis of variance (ANOVA) and multivariate analysis of variance with canonical analysis (MANOVA) was used to evaluate sources of variation. Variation in arabinoxylan contents and absolute amounts (xylose equivalents) among the two cultivar sample sets (spring and winter) was similar, and both cultivar and environment were significant sources of variation. The cultivar‐by‐environment interaction was relatively unimportant. Results indicate that the variation in arabinoxylan content is primarily influenced by cultivar and secondarily influenced by environment. Within arabinoxylan fractions, WS‐AX content is primarily influenced by genotype, while WI‐AX content is more greatly influenced by the environment.