Starch Granules In Endosperm Research Articles

Drying Damage on Physiological Properties of Rice Seed Associated with Ultrastructure Changes

Abstract The aim of the present study was to investigate the alterations of the physiological properties associated with the ultrastructure changes of rice seed after drying at different temperatures. The drying process was accomplished at 30, 45, 60, 75 and 90°C and at 29.3%, 13.0%, 6.4%, 3.2%, and 1.8% relative humidity, respectively. As a result, the germination percentage of the rice seeds was reduced as the increasing of the drying temperature and the highest value of vigor index was recorded at 45°C due to the dormancy breakage. There were no changes in the color of the raw rice seed dried at different temperatures; however, the yellowness of the brown rice and the electrical conductivity increased with the increasing drying temperature. The starch granules of the rice endosperm dried at 45°C were wrinkled and wilted and this damage occurred with high intensity after drying at temperatures above 60°C. The structure of the starch granules eventually became rupture when the drying temperature reached to 90°C. The cells of the rice embryo presented a contraction of their volumes drying at temperatures above 45°C due to the degradation of the middle lamella. The form of the oil drops was also altered after drying. At temperature above 75°C, the drops broke up and coalesced. It was concluded that the physiological quality of rice seed was closely associated with the alterations of cell structure during drying process.

Comparison of Flour Starch Properties in Half‐Sib Families of Opaque‐2 Maize (Zea mays L.) from Argentina

Since the discovery of the o2 mutation in maize, many studies have reported the characterization of the protein quality of opaque‐2 genotypes. However, few have reported the properties of their starch. The objective of this study was to characterize flour starch properties of 12 half‐sib families of opaque‐2 maize from Argentina. Chemical composition and thermal and pasting properties of whole grain flour were determined. Nonopaque genotypes were used as a control. Starch content of opaque‐2 genotypes did not show significant differences compared with nonopaque genotypes, yet amylose content was significantly lower. A high variability in pasting and thermal properties was observed in genotypes. Opaque samples showed a significantly higher peak viscosity and a lower pasting temperature compared with nonopaque samples, probably owing to larger and less compact starch granules in the floury endosperm. The higher the gelatinization enthalpy of opaque‐2 genotypes was, the lower the amylose content in relation to nonopaque varieties. Two retrogradation endotherms were observed in DSC analysis: one corresponding to amylopectin crystallization and the other to melting of amylose‐lipid complex. Both enthalpies were considered total starch retrogradation (ΔHRT). A wide range of variation was obtained in ΔHRT in opaque‐2 genotypes, but no significant differences between opaque and nonopaque genotypes were observed. The differences in starch properties found in this study would make it possible to identify opaque‐2 families with particular characteristics for the development of starchy food items adapted to specific processing traits.

Proteomic Dissection of Endosperm Starch Granule Associated Proteins Reveals a Network Coordinating Starch Biosynthesis and Amino Acid Metabolism and Glycolysis in Rice Endosperms.

Starch biosynthesis and starch granule packaging in cereal endosperms involve a coordinated action of starch biosynthesis enzymes and coordination with other metabolisms. Because directly binding to starch granules, starch granule-associated proteins (SGAPs) are essential to understand the underlying mechanisms, however the information on SGAPs remains largely unknown. Here, we dissected developmentally changed SGAPs from developing rice endosperms from 10 to 20 days after flowering (DAF). Starch granule packaging was not completed at 10 DAF, and was finished in the central endosperm at 15 DAF and in the whole endosperm at 20 DAF. Proteomic analysis with two-dimensional differential in-gel electrophoresis and mass spectrometry revealed 115 developmentally changed SGAPs, representing 37 unique proteins. 65% of the unique proteins had isoforms. 39% of the identified SGAPs were involved in starch biosynthesis with main functions in polyglucan elongation and granule structure trimming. Almost all proteins involved in starch biosynthesis, amino acid biosynthesis, glycolysis, protein folding, and PPDK pathways increased abundance as the endosperm developed, and were predicted in an interaction network. The network represents an important mechanism to orchestrate carbon partitioning among starch biosynthesis, amino acid biosynthesis and glycolysis for efficient starch and protein storage. These results provide novel insights into mechanisms of starch biosynthesis and its coordination with amino acid metabolisms and glycolysis in cereal endosperms.

Elevated Ozone Deteriorates Grain Quality of Japonica Rice cv. Koshihikari, Even if it Does Not Cause Yield Reduction.

BackgroundIt is becoming clear that ozone affects not only grain yield but also grain quality in rice. However, the biochemical mechanisms responsible for ozone-induced changes in appearance quality or components are poorly understood. We analyzed appearance quality and starch composition in the rice cultivars “Koshihikari” (japonica) and “Kasalath” (indica) grown under elevated ozone conditions.ResultsElevated ozone significantly increased the proportion of immature (mainly chalky) kernels in “Koshihikari” but not in “Kasalath”. Scanning electron microscopy of transverse sections of kernels showed that endosperm starch granules of “Koshihikari” ripened under elevated ozone were loosely packed with large spaces and contained irregular rounded granules. Amylose content was increased in “Koshihikari” kernels with ozone exposure, but was unchanged in “Kasalath” kernels. Distribution analysis of amylopectin chain length showed that ozone induces a decrease of long-side chains and alterations of short side-chains in “Koshihikari” kernels. Furthermore, Starch Synthase (SS) IIIa transcript levels in “Koshihikari” caryopses were decreased by elevated ozone.ConclusionsThe japonica cultivar “Koshihikari” showed significant deterioration in appearance quality of kernels caused by abnormal starch accumulation due to exposure to ozone. The alteration patterns of amylose and amylopectin in ozone-exposed rice kernels are similar to those in rice kernels harvested from SSIIIa-deficient mutants. These findings suggest that the increase of chalky kernels in ozone-treated “Koshihikari” is partly attributable to the repressed expression of SSIIIa involved in amylopectin side-chain elongation with ozone exposure. Elevated ozone reduced appearance quality in “Koshihikari” although it did not impair starch properties contributing to the eating quality of cooked rice.Electronic supplementary materialThe online version of this article (doi:10.1186/s12284-016-0079-4) contains supplementary material, which is available to authorized users.

Plastidial Disproportionating Enzyme Participates in Starch Synthesis in Rice Endosperm by Transferring Maltooligosyl Groups from Amylose and Amylopectin to Amylopectin.

Plastidial disproportionating enzyme1 (DPE1), an α-1,4-d-glucanotransferase, has been thought to be involved in storage starch synthesis in cereal crops. However, the precise function of DPE1 remains to be established. We present here the functional identification of DPE1 in storage starch synthesis in rice (Oryza sativa) by endosperm-specific gene overexpression and suppression. DPE1 overexpression decreased amylose content and resulted in small and tightly packed starch granules, whereas DPE1 suppression increased amylose content and formed heterogeneous-sized, spherical, and loosely packed starch granules. Chains with degree of polymerization (DP) of 6 to 10 and 23 to 38 were increased, while chains with DP of 11 to 22 were decreased in amylopectin from DPE1-overexpressing seeds. By contrast, chains with DP of 6 to 8 and 16 to 36 were decreased, while chains with DP of 9 to 15 were increased in amylopectin from DPE1-suppressed seeds. Changes in DPE1 gene expression also resulted in modifications in the thermal and pasting features of endosperm starch granules. In vitro analyses revealed that recombinant DPE1 can break down amylose into maltooligosaccharides in the presence of Glc, while it can transfer maltooligosyl groups from maltooligosaccharide to amylopectin or transfer maltooligosyl groups within and among amylopectin molecules in the absence of Glc. Moreover, a metabolic flow of maltooligosyl groups from amylose to amylopectin was clearly identifiable when comparing DPE1-overexpressing lines with DPE1-suppressed lines. These findings demonstrate that DPE1 participates substantially in starch synthesis in rice endosperm by transferring maltooligosyl groups from amylose and amylopectin to amylopectin.

Effect of drought stress on the development of endosperm starch granules and the composition and physicochemical properties of starches from soft and hard wheat.

The objectives of this study were to: (1) observe the effects of drought stress (DS) on the structural development of endosperm starch granules; (2) investigate the effects of DS on composition and physicochemical properties of starches; and (3) compare the different responses to DS between soft and hard wheat. DS resulted in large A-type starch granules at 12 d after anthesis (DAA) and a high percentage of B-type starch granules at 18 DAA in endosperm cells of the two wheat cultivars. DS decreased the 1000-grain weight, total starch and amylose contents, and amylose-to-amylopectin ratio of both starches. DS also decreased the percentage of B-type starch granules in NM13 and increased the number of hollows on the surface of A-type starch granules in XM33. DS further increased the swelling power and affected pasting properties of both starches. DS also significantly enhanced the hydrolysis degrees of starches by pancreatic α-amylase, Aspergillus niger amyloglucosidase, and HCl in NM13. DS altered the contents of rapidly digestible, slowly digestible, and resistant starches in native, gelatinised, and retrograded starches. Overall, DS can affect the development of endosperm starch granules and the physicochemical properties of starches, thus affecting the qualities of the final wheat products. © 2015 Society of Chemical Industry.

Internal structure of amylopectin from the pericarp tissue of developing wheat kernels

Pericarp starch is a transient starch that forms in the developing wheat kernel and decomposes concurrently with the appearance of the endosperm. The detailed structure of the amylopectin component of pericarp starch granules was investigated and compared with amylopectin from mature wheat endosperm. Clusters of chains from the macromolecule were isolated by hydrolysis with α‐amylase from Bacillus amyloliquefaciens and were then transformed to limit dextrins using phosphorylase and β‐amylase. The pericarp clusters consisted of 14.2 chains on average and had a 16.1% degree of branching, which was similar to the characteristics of clusters from large endosperm starch granules, as was the composition of the branched building blocks. However, the pericarp clusters exhibited a somewhat lower number of the largest building blocks. Other structural attributes, such as the average number of building blocks in the clusters and the length of the interblock segments, were also similar to those of endosperm starch. It is concluded that the cluster structure of wheat pericarp amylopectin essentially matches that of its endosperm counterpart.

Comparison of Endosperm Starch Granule Development and Physicochemical Properties of Starches from Waxy and Non-Waxy Wheat

Starch granule development and physicochemical properties of starches in waxy wheat and non-waxy wheat were investigated in this article. Starch granules in waxy wheat endosperm showed an early developmental process. Compared with non-waxy wheat starch granules (round-shaped), waxy wheat starch granules (ellipse-shaped) were larger and contained more B-type granules. According to the granule size, starch granules were divided into two groups in waxy wheat, but were divided into three groups in non-waxy wheat. Compared with non-waxy wheat starch, waxy wheat starch had higher swelling power, gelatinization temperatures (To, Tp, Tc), and relative degree of crystallinity. They showed similar ordered structures on external regions of starch granules. Additionally, waxy wheat starch had a higher proportion of double-helical components and a lower proportion of single-helical components than non-waxy wheat starch. Based on the previous results, it was concluded: (1) waxy wheat and non-waxy wheat not only differed in starch granule development, but also in physicochemical properties of starches; (2) waxy wheat had more potential value for producing traditional products than non-waxy wheat.

Differences of starch granule distribution in grains from different spikelet positions in winter wheat.

Wheat starch development is a complex process and is markedly difference by changes in spikelet spatial position. The present study deals with endosperm starch granule distribution and spatial position during filling development. The study was conducted with pure starch isolated from wheat (Triticum aestivum L.), Jimai20 and Shannong1391, at 7–35 days after anthesis (DAA). The results showed that grain number, spikelet weight and grain weight per spikelet in different spatial position showed parabolic changes. Upper spikelets had highest starch and amylose content followed by basal spikelets, then middle spikelets. The paper also suggested the volume percents of B-type and A-type granule in grain of middle spikelets were remarkably higher and lower than those of basal and upper spikelets, respectively. However, no significant difference occurred in the number percents of the two type granule. The ratio of amylase to amylopectin was positively correlated with the volume proportion of 22.8–42.8 µm, but was negatively related to the volume proportion of <9.9 µm. The results indicated that the formation and distribution of starch granules were affected significantly by spikelet position, and grains at upper and basal spikelet had the potential of increasing grain weight through increasing the volume of B-type granules.

Effect of nitrogen fertilizer on distribution of starch granules in different regions of wheat endosperm

This study provided visual evidence of a nitrogen effect on starch granules (SGs) in wheat endosperm. Winter wheat (Titicum aestivum L.) cultivar Xumai 30 was cultured under no nitrogen (control) and 240kgha−1 of nitrogen applied at the booting stage. The number, morphology, and size of A- and B-type SGs in subaleurone of dorsal endosperm (SDE), center of dorsal endosperm (CDE), modified aleurone (MA), subaleurone of ventral endosperm (SVE), and center of ventral endosperm (CVE) were observed under light and electron microscopes. (1) The distribution of SGs in SDE was similar to that in SVE, the distributions of SGs in CDE and CVE were similar, but the distribution of SGs in MA was different from those in the other four endosperm regions. The number of SGs in the five endosperm regions was in the order SDE>CDE>SVE>CVE>MA. (2) Nitrogen increased the number of A- and B-type SGs in SDE and SVE. Nitrogen also increased the number of B-type SGs but decreased the number of A-type SGs in CDE and CVE. Nitrogen decreased the numbers of A-type and B-type SGs in MA. The results suggest that increased N fertilizer application mainly increased the numbers of small SGs and decreased the numbers of large SGs, but that the results varied in different regions of the wheat endosperm.

Differences of Starch Granules in Grains from Different Spikelet Positions and Their Correlation with Grain Weight in Winter Wheat

The purpose of this study was to reveal the differences in development and size-distribution of starch granules in endosperm of wheat grains in different grain positions and spikelet positions. The endosperm cell size, and the number, volume and surface area distribution of starch granules in mature caryopsis, as well as the changes of starch granule number during endosperm development, were studied using wheat cultivar Jimai 20 grown in the field. The results showed that the development of starch granule was closely related with grain position and spikelet position. In the same spikelet position, starch grains formed 4–5 d earlier in superior grains (the first and the second grains) than in inferior grains (the third and the fourth grains).At the same grain position, starch granules developed first in the grains of the middle spikelets, and then in grains of upper and lower spikelets. The amount of starch granules was the highest in the middle spikelet grains all the time. The lower spikelet grains had the least starch granules at the beginning of grain filling, however, the number of starch granules increased gradually and surpassed that of the upper spikelet grains as caryopsis matured. Correlation coefficients between grain weight and starch granule amount became more significant with grain filling, which reached 0.88 ** (large starch granule) and 0.78 ** (small starch granule) at mature stage. Correlation coefficients between grain weight and large starch granule amount were higher than 0.96 ** , and had no difference among different spikelet positions. Correlation coefficients between grain weight and small starch granule amount were higher than 0.93 ** , and had a trend of upperlowermiddle in different spikelet positions. The trend of size distribution was BL-typeBS-typeA-type. There were more BS-type granules in superior grains than in inferior grains. The number of BS-type granules increased with the spikelet position rising, whereas the number of BL-type granules showed a reverse trend. The size distribution of starch granules had similar changes to volume and surface area. The formation and size distribution of starch granules were affectedsignificantly by grain position and spikelet position, and inferior grains had the potential of increasing grain weight through increasing the quantity of starch granules.

Related physicochemical properties to microstructure of hard and soft wheat grains with different kernel thickness and specific density

Physicochemical properties of wheat grains with largest kernel thickness always was lowest than the other sections, examination of microstructure of wheat grains can help us understand this phenomena. Two varieties of wheat, soft white winter wheat Yangmai 11 and hard white winter wheat Zhengmai 9023, were fractionated into five sections by kernel thickness. Then the fractionated wheat grains in 2.7-3.0 mm section were separated into three fractions by kernel specific density sequentially. Microstructure of the fractured surface were evaluated at different scale level to two varieties wheat with different kernel thickness and specific density by using environmental scanning electron microscopy. Compactness and size of endosperm cell tended to decrease with decreasing wheat kernel thickness and specific density. Protein matrix tended to increase with decreasing wheat kernel thickness and specific density. Size of starch granules and proportion for different type starch granules also varied with different wheat kernel thickness and specific density. Those microstructure properties of the fractured surface, formation of endosperm cells, protein matrix and starch granules were close related to rheological properties and pasting properties of wheat grains.

Barley callus: a model system for bioengineering of starch in cereals

BackgroundStarch is the most important source of calories for human nutrition and the majority of it is produced by cereal farming. Starch is also used as a renewable raw material in a range of industrial sectors. It can be chemically modified to introduce new physicochemical properties. In this way starch is adapted to a variety of specific end-uses. Recombinant DNA technologies offers an alternative to starch industrial processing. The plant biosynthetic pathway can be manipulated to design starches with novel structure and improved technological properties. In the future this may reduce or eliminate the economical and environmental costs of industrial modification. Recently, many advances have been achieved to clarify the genetic mechanism that controls starch biosynthesis. Several genes involved in the synthesis and modification of complex carbohydrates in many organisms have been identified and cloned. This knowledge suggests a number of strategies and a series of candidate genes for genetic transformation of crops to generate new types of starch-based polymers. However transformation of cereals is a slow process and there is no easy model system available to test the efficiency of candidate genes in planta.ResultsWe explored the possibility to use transgenic barley callus generated from immature embryo for a fast test of transgenic modification strategies of starch biosynthesis. We found that this callus contains 4% (w/w dw) starch granules, which we could modify by generating fully transgenic calli by Agrobacterium-transformation. A Green Fluorescent Protein reporter protein tag was used to identify and propagate only fully transgenic callus explants. Around 1 – 1.5 g dry weight of fully transgenic callus could be produced in 9 weeks. Callus starch granules were smaller than endosperm starch granules and contained less amylose. Similarly the expression profile of starch biosynthesis genes were slightly different in callus compared with developing endosperm.ConclusionsIn this study we have developed an easy and rapid in planta model system for starch bioengineering in cereals. We suggest that this method can be used as a time-efficient model system for fast screening of candidate genes for the generation of modified starch or new types of carbohydrate polymers.

Effect of Temperature during Grain Filling Stage on Endosperm Structure and Apperance Quality of Aromatic Rice

Based on the experiment of two inbred aromatic rice varieties and one hybrid aromatic rice line treated under four different temperatures( daymean temperature 21°C, 23°C, 26°C and 30°C respectively) during grain filling stage in phytotrons, the shape and arrangement of endosperm starch granules in rice grain transection were observed by scanning electron microscope and the related characteristics of rice grain qualities of chalky percent and chalkiness were analyzed at the same time. The results showed that under the lower temperature( daymean temperature21°C and 23°C), many large compound starch granules with clear angulars packed together regularly without significant natural gaps bewteen starch granules in the tansectional endosperm. However, with the increase of temperature, starch granules in the transectional endosperm were changed from regularly shaped and closely and orderly arranged to various shaped and chaoticly arranged with obvious natural gaps between starch granules, which was closely consistent with the poorer appearance quality under the higher temperature, which indicated that the endosperm structure is closely related with appearance quality of aromatic rice.

Comparative Proteomic Study Reveals the Involvement of Diurnal Cycle in Cell Division, Enlargement, and Starch Accumulation in Developing Endosperm ofOryza sativa

The development and starch accumulation of cereal endosperms rely on the sugar supply of leaves, which is subject to diurnal cycles, and the endosperm itself also experiences a light/dark switch. However, revealing how the cereal endosperm responds to diurnal input remains a major challenge. We used comparative proteomic approaches to probe diurnally affected processes in rice endosperm (Oryza sativa) 10 days after flowering under 12-h light/12-h dark. Starch granules in rice endosperm showed a growth ring structure under a normal light/dark cycle but not under constant light. Sucrose showed a high level in light and low level in dark. Two-dimensional (2-D) differential in-gel electrophoresis-based proteomic analysis revealed 101 protein spots diurnally changed and 91 identities, which were involved in diverse processes with preferred distribution in stress response, protein synthesis/destination and metabolism. Proteins involved in cell division showed high expression in light and those in cell enlargement and cell wall synthesis high in dark, while starch synthesis proteins were light-downregulated and dark-upregulated. Redox homeostasis-associated proteins showed in-phase peaks under light and dark. These data demonstrate diurnal input-regulated diverse cellular and metabolic processes in rice endosperm, and coordination among these processes is essential for development and starch accumulation with diurnal input.

Elucidation of maize endosperm starch granule channel proteins and evidence for plastoskeletal structures in maize endosperm amyloplasts

Previously, starch granules of maize ( Zea mays), sorghum ( Sorghum bicolor), and millet ( Pennisetum americanum) were found to contain channels connecting the interior cavity with the outside surface, and the channels of maize starch channels were found to contain, presumably to be lined with, proteins. One objective of this study was to identify and characterize channel proteins of maize starch granules. A putative starch granule channel protein extract was subjected to 2D-PAGE. Matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry was used to identify the proteins. Data analysis indicated the presence of actin-like and tubulin-like (FtsZ) proteins, ADP-glucose pyrophosphorylase large and small subunits (Shrunken2 [Sh2] and Brittle2 [Bt2], respectively), granule-bound starch synthase (GBSS), and Brittle1 (Bt1, an adenylate translocator). A combination of Western blot analysis and immunolocalization confirmed the presence of an actin-like protein within the starch granule structure. Another objective was to determine the origin of maize starch granule channels. TEM examination of maize endosperm amyloplasts that did not contain a formed starch granule revealed structures that were connected to the amyloplast membrane and extended inward to the center of the plastid.

Molecular basis of the waxy endosperm starch phenotype in broomcorn millet (Panicum miliaceum L.).

Waxy varieties of the tetraploid cereal broomcorn millet (Panicum miliaceum L.) have endosperm starch granules lacking detectable amylose. This study investigated the basis of this phenotype using molecular and biochemical methods. Iodine staining of starch granules in 72 plants from 38 landrace accessions found 58 nonwaxy and 14 waxy phenotype plants. All waxy types were in plants from Chinese and Korean accessions, a distribution similar to that of the waxy phenotype in other cereals. Granule-bound starch synthase I (GBSSI) protein was present in the endosperm of both nonwaxy and waxy individuals, but waxy types had little or no granule-bound starch synthase activity compared with the wild types. Sequencing of the GBSSI (Waxy) gene showed that this gene is present in two different forms (L and S) in P. miliaceum, which probably represent homeologues derived from two distinct diploid ancestors. Protein products of both these forms are present in starch granules. We identified three polymorphisms in the exon sequence coding for mature GBSSI peptides. A 15-bp deletion has occurred in the S type GBSSI, resulting in the loss of five amino acids from glucosyl transferase domain 1 (GTD1). The second GBSSI type (L) shows two sequence polymorphisms. One is the insertion of an adenine residue that causes a reading frameshift, and the second causes a cysteine–tyrosine amino acid polymorphism. These mutations appear to have occurred in parallel from the ancestral allele, resulting in three GBSSI-L alleles in total. Five of the six possible genotype combinations of the S and L alleles were observed. The deletion in the GBSSI-S gene causes loss of protein activity, and there was 100% correspondence between this deletion and the waxy phenotype. The frameshift mutation in the L gene results in the loss of L-type protein from starch granules. The L isoform with the tyrosine residue is present in starch granules but is nonfunctional. This loss of function may result from the substitution of tyrosine for cysteine, although it could not be determined whether the cysteine isoform of L represents the functional type. This is the first characterization of mutations that occur in combination in a functionally polyploid species to give a fully waxy phenotype.

The effects of puroindoline b on the ultrastructure of endosperm cells and physicochemical properties of transgenic rice plant

Endosperm texture is an important factor governing the end-product quality of cereals. The texture of wheat ( Triticum aestivum L.) endosperm is controlled by puroindoline a and b genes which are both absent in rice ( Oryza sativa L.). It has been reported that the endosperm texture of rice can be modified by puroindoline genes. The mechanism, however, by which puroindolines affect the ultrastructure of rice endosperm cells remains to be investigated. In this study, we observed the ultrastructure of endosperm cells and the morphology of isolated starch granules of the transgenic rice expressing the puroindoline b gene. SEM and TEM observations indicated that compound starch granules were embedded within the matrix material in non-transgenic rice, Nipponbare, whereas they were surrounded by spaces in the transgenic rice. The morphology and size of each starch granule were not different between non-transgenic and the transgenic rice. However, the transgenic rice flour showed smaller particle size, higher starch damage, and lower viscosity during gelatinization than that of non-transgenic rice. These results confirm that puroindoline b reduces the grain hardness in rice. Moreover, the results also suggest that puroindoline b functions at the surface of compound starch granules, and not on polygonal starch granules in rice endosperm.

Chain‐length Distribution Profiles of Amylopectin Isolated from Endosperm Starch of Waxy and Low‐amylose Bread Wheat (Triticum aestivum L.) Lines with Common Genetic Background

AbstractLarge A‐type endosperm starch granules were isolated from near‐isogenic waxy and non‐waxy lines and low‐amylose mutant lines of bread wheat with a common genetic background. The amylose contents of A‐type starch ranged from 2.6% to 23.6%. Amylopectin was isolated by concanavalin A (Con A) precipitation from the isolated starch. The λmax (range: 532‐538 nm) and blue values at 680 nm (range: 0.026‐0.037) of the iodine‐amylopectin complex were not significantly different among the isolated amylopectins, indicating that amylopectins from non‐waxy and low‐amylose lines did not contain such long chains as amylose or extra‐long chains of amylopectin affecting iodine complex properties. Chain‐length distribution profiles measured by both high‐performance size‐exclusion chromatography (HPSEC) and high‐performance anion‐exchange chromatography (HPAEC) showed that the amylopectin structures of these lines were indistinguishable from each other. Extra‐long chains were not detected in the amylopectins by HPSEC measurement. The side‐chains measured by HPAEC were classified into four groups according to their degree of polymerization (DP), and the proportion of each group were in the following ranges: DP 6‐12, 26.5‐27.5%; DP 13‐24, 43.6‐44.1%; DP 25‐36, 13.6‐14.2%, and DP 37‐60, 11.0‐11.7%. The alleles on the Wx‐D1 locus, i.e., Wx‐D1a, Wx‐D1d, Wx‐D1f, and Wx‐D1g, responsible for granule‐bound starch synthase (GBSS I) biosynthesis had no influence on the properties of iodine‐amylopectin complex and the chain‐length distribution profiles of amylopectin.

Hormonal changes in grains of cv. Triumph and its mutant TL43 as affected by nitrogen fertilizer at heading time

A pot experiment was conducted to study the hormonal changes during the grain filling stage in barley lines of Triumph and its mutant TL43 with or without nitrogen fertilizer at heading time. The ABA, ZR and IAA contents in grains were higher under nitrogen treatment (HN) for both genotypes at 30 days post anthesis (DPA). No genotypic differences were observed in GA 3, ABA and IAA content over the grain filling stage and ZR content on 10 DPA exhibited the major difference, which might be associated with the decrease of A-type starch granules in endosperm of TL43. Triumph also showed significantly higher grain weight, lower hordein and glutelin contents than TL43. The changes of these characters might be correlated with the ZR deficiency of TL43 at early grain filling stage.