Studies on the Cereal Starches

Twenty purified rice starches of domestic and imported rices from eight countries including indica and japonica subspecies were submitted to the test of the chemical compositions, pasting characteristics and dynamic visco-elasticity of cold paste body. High correlations were found between some of these characteristics in which were observed obvious differences among the samples. For characterization of rice starches, the samples were classified in 4 groups, according to the degree of these starch characters, which were roughly expressed as “Sticky type” and “Non-sticky or Flaky type”     

X-Ray Diffractometric Studies on Starches

A linear amylodextrin (average degree of polymerization 12.6) from sweetpotato was crystallized at different temperatures and from different concentrations of solution, and the crystalline type of the recrystallized amylodextrin was examined by X-ray diffraction. It was shown that the crystal type was dependent on the crystallization conditions. The conditions required for the formation of A-, C- and B-type crystals were limited by the following functional relations: 2.5T+C>84, 72<2.5T+C<84, and 2.5T+C<72, respectively, where T is the temperature (°C) at which the amylodextrin was crystallized and C is the concentration (%) of the amylodextrin solution. This relation showed that high temperatures and high concentrations of amylodextrin were favorable for A-type crystal formation and low temperatures and concentrations for B-type crystals, and that the type of crystals formed was more affected by temperature than concentration of the solution.     

禾本科作物芒遗传研究进展

芒是许多禾本科作物穗部的重要结构, 不仅可以作为区分不同品种以及基因定位的重要形态标记, 而且在禾谷类作物的种子传播、籽粒灌浆、蒸腾作用及产量形成等方面起重要作用。该文综述了小麦(Triticum aestivum)、大麦(Hordeum vulgare)和水稻(Oryza sativa)芒的结构、功能与遗传调控机制研究进展, 以期为芒性状遗传机理的进一步研究及其在育种中的应用提供参考。     

Studies of Cereal α-Amylases Using Cloned Dna

Abstract

Different types of enzyme-catalyzed processes are reviewed, with particular regard to those procedures leading to the generation of chiral compounds of high optical purity. The main body of the review deals with hydrolyses and esterifi-cation as well as the reduction and oxidation of organic substrates. Other biotransformations of current and/or future importance in the synthesis of homochiral fine chemicals (such as the formation of carbon-carbon bonds using aldolases) are also discussed in some detail. Attention is drawn to current trends in the area and, to this end, a majority of the references are taken from journals published during the period April 1987 to September 1988.     

Cereal breeding takes a walk on the wild side

Elite cultivated crop gene pools of the Triticeae tribe (wheat, barley and rye) exhibit limited genetic diversity, raising concerns about our ability to increase or simply sustain crop yield and quality in the face of dynamic environmental and biotic threats. Although exploiting their wild relatives as a source of novel alleles is challenging, it has provided notable successes in cereal improvement for >100 years. Increasingly facile gene discovery, improved enabling technologies for genetics and breeding and a better understanding of the factors limiting practical exploitation of exotic germplasm promise to transform existing, and accelerate the development of new, strategies for efficient and directed germplasm utilization.     

Cereal protoplast recalcitrance

Summary Cereal leaf protoplasts are extremely difficult to culture (recalcitrant) in vitro. There have been few reports of division and the protoplasts typically exhibit excessive enlargement and vacuolization with reduced cell wall deposition. Inasmuch as leaf base explants are capable of callus formation in vitro, protoplasts derived from this tissue must have lost the ability to divide as a consequence of changes induced by the wall-digestion process. We review evidence suggesting that the inhibition of mitosis in these protoplasts is a consequence of a cascade of events initiated at the plasma membrane. The enzyme treatment necessary for wall removal triggers membrane depolarization and other changes that can lead to the initiation of lipid peroxidation and oxidative stress. Mitotically inactive cereal leaf protoplasts are unable to mount a protective response to these degradative processes. Consequently, the resulting membrane perturbations and permeabilization give rise to secondary effects on the cytoskeleton and the cell wall. These effects include reduced or absent microtubules as well as reduced and uneven wall deposition. Such abnormalities are observed in cereal leaf protoplasts and are sufficient to account for recalcitrance because the occurrence of mitosis is strongly dependent on a normal cell wall and cytoskeleton. This paper is NRCC number 32475.     

Cereal aphids on maize in southern England

In 1978, 1979 and 1980, counts were made of the numbers of cereal aphids on a maize crop near Fordingbridge, Hampshire, England. Maize plants were selected away from the edge of the crop and the number, morph, species and feeding site of the aphids were recorded. Metopolophium dirhodum and Rhopalosiphum padi were found at densities that exceeded those found on small-grain cereals and grasses at the same time of the year. Sitobion avenae and Macrosiphum euphorbiae were found at relatively low densities, and Rhopalosiphum maidis and Metopolophium festucae were observed rarely. Unlike other species, the numbers of R. padi continued to increase throughout the summer and reached a peak in September/October; at this time of the year, R. padi constituted over 98% of the aphids found on maize. M. dirhodum and S. avenae were found mostly on the leaves whereas R. padi appeared to favour the cob until populations became too large to be supported. If the area of maize grown in the UK increases, the crop will probably play an important role in the life cycle of cereal aphids (especially R. padi ). It is suggested that further work should be carried out on the pest status of aphids on maize and on the role that maize may play in the ecology of cereal pests.     

Calorimetric Studies on α-1,4 Glucosidic Linkage Content in Sweet Potato Starches at Two Different Stages of Development

In the latest work, a method to determine calorimetrically the α-glucosidic linkage contents in starches was introduced.

The present work refers to the application of this method to the determination of the α-1,4 glucosidic linkage content in two kinds of sweet potato starch (i.e., Norin-1 and Okinawa-100) isolated at the two different stages of development.

It has been found that the sample isolated on October 31 (1953) had a larger value for α-1,4 glucosidic linkage content than the sample isolated on August 6 (1953) for both the two sweet potato starches.

Combined with the amperometric titration method the increase in α-1,4 glucosidic linkage content has been found to be due to both the increases in amylose content and in average unit chain length of amylopectin component.     

Submicroscopic Structure of the Cereal Starch Grain

The submicroscopic structure of the starch grains of Zea maysand Triticum sativum was studied electron-optically from replicasmade of internal, fracture surfaces. In corn starch, long cylindricalmicrofibrils were found, arranged in a radial direction andimbedded in an amorphous matrix. Their diameter was uniformlyabout 200 Å. Microfibrils were also indicated in wheatstarch because of the prominence of their ends in surface view.Many microfibrils in corn starch appeared to be helically coiled.The more ordered starch substance was presumed to be localizedprincipally in the microfibrils.     

Cereal asparagine synthetase genes

Asparagine synthetase catalyses the transfer of an amino group from glutamine to aspartate to form glutamate and asparagine. The accumulation of free (nonprotein) asparagine in crops has implications for food safety because free asparagine is the precursor for acrylamide, a carcinogenic contaminant that forms during high‐temperature cooking and processing. Here we review publicly available genome data for asparagine synthetase genes from species of the Pooideae subfamily, including bread wheat and related wheat species (Triticum and Aegilops spp.), barley (Hordeum vulgare) and rye (Secale cereale) of the Triticeae tribe. Also from the Pooideae subfamily: brachypodium (Brachypodium dIstachyon) of the Brachypodiae tribe. More diverse species are also included, comprising sorghum (Sorghum bicolor) and maize (Zea mays) of the Panicoideae subfamily and rice (Oryza sativa) of the Ehrhartoideae subfamily. The asparagine synthetase gene families of the Triticeae species each comprise five genes per genome, with the genes assigned to four groups: 1, 2, 3 (subdivided into 3.1 and 3.2) and 4. Each species has a single gene per genome in each group, except that some bread wheat varieties (genomes AABBDD) and emmer wheat (Triticum dicoccoides; genomes AABB) lack a group 2 gene in the B genome. This raises questions about the ancestry of cultivated pasta wheat and the B genome donor of bread wheat, suggesting that the hybridisation event that gave rise to hexaploid bread wheat occurred more than once. In phylogenetic analyses, genes from the other species cluster with the Triticeae genes, but brachypodium, sorghum and maize lack a group 2 gene, while rice has only two genes, one group 3 and one group 4. This means that TaASN2, the most highly expressed asparagine synthetase gene in wheat grain, has no equivalent in maize, rice, sorghum or brachypodium. An evolutionary pathway is proposed in which a series of gene duplications gave rise to the five genes found in modern Triticeae species.     

The Effect of Wilting on the Redox Potential of Cereal Leaves

The redox potential of wilted leaves of cereal seedlings grown in a greenhouse was higher than in the fresh leaves. However, the redox potential in the wilted leaves of plants during the stem extension was lower than in fresh leaves. The reaction of barley leaves var. Japan 2003, which belongs to the dundar-beyi Zhuk.-group, differed materially from the European cereal varieties. The cause of the change of redox potential is discussed in connection with the ontogeny of cereals and resistance against obligate parasites.     

谷物籽粒淀粉研究进展

谷物籽粒是人类最基本的粮食,其胚乳淀粉与品质有密切的关系.本文就谷物胚乳淀粉的合成积累过程、谷物淀粉合成酶的作用与特性、淀粉特性与品质的关系以及基因工程在改良作物淀粉品质方面的研究进展进行了综述,并对谷物籽粒淀粉进一步的研究提出了展望,为谷物淀粉品质育种提供参考.     

Field Studies of Cereal Leaf Growth: I. INITIATION AND EXPANSION IN RELATION TO TEMPERATURE AND ONTOGENY

Measurements of leaf initiation, appearance, and expansion arepresented for winter wheat and spring barley crops. For winterwheat, these processes occurred during periods of several weekswhen fluctuating temperatures influenced process rates. Analysisof these measurements was facilitated by plotting variablesagainst the time integral of temperature above an appropriatebase temperature (O °C), here called thermal time with unitsof °C d. Leaf primordial number and appearance stage increasedlinearly with thermal time for both winter wheat and springbarley which initiated 12 and 9 leaves respectively. When plottedagainst thermal time 90% of laminar and leaf length growth and80% of laminar width growth was satisfactorily described bya straight line for both species. This enabled an average extensionrate and duration of linear growth to be defined for each leaf.When expressed in thermal time, wheat leaves had a similar durationof linear growth (210 °C d; s.d. 30 °C d) with insolationexerting a negligible influence. The first seven barley leaveshad a shorter duration of linear growth (151 °C d; s.d.8 °C d). For wheat, final leaf length and laminar widthincreased with leaf number and were not apparently associatedwith changes in apical development stage. Changes of barleyleaf dimensions with leaf number were more complex.     

高效液相色谱法测定粮食作物中的色氨酸

用ＨＰＬＣ法测定粮食作物中的色氨酸,实验采用阳离子交换柱,以０．１ｍｏｌ／ＬＣＨ３ＣＯＯＮＨ４为流动相,荧光检测器中ｅｘ２８０ｎｍ,ｅｍ３４０ｎｍ检测,色氨酸和酪氨酸分离很好,回收率在９５％以上。     

重要禾谷类植物转基因研究

与双子叶植物相比,禾谷类植物的离体培养和再生主要采用一些胚性组织,对它们的转基因研究发展相对比较缓慢。90年代以来,离体培养方面的经验被有效地融入DNA转移技术;通过筛选和再生少量的转化细胞,已得到了不少可育的小麦、水稻、玉米、大麦等禾谷类转基因植物。本文着重综述了禾谷类植物转化方法和选择体系方面的研究现状,同时讨论了该研究方向的未来发展趋势。     

空间条件对几种粮食作物的同工酶和细胞学特性的影响

搭载１９８７年发射的两颗返地卫星（８月５—１０日和９月９—１７日）的几种小麦、大麦种子,经回收后初步研究表明：（１）对发芽率的影响：空间处理的种子,其发芽率与对照无差别;（２）对茎及生育期的影响：空间处理的种子长成的幼苗比对照强壮,植株高度有些品种明显的矮于对照。生育期有不同程度延长;（３）对染色体结构的影响：花粉母细胞减数分裂观察表明搭载卫星的种子当代可诱导出比地面更多的染色体桥、落后染色体及染色体数目异于正常体细胞数目的现象。小麦品种Ｃｏｃｏｒｉｔ—７１经空间处理后花粉母细胞的染色体数目异常可高达２０．５１％,而地面对照组其花粉母细胞基本正常（２ｎ＝２８）;（４）对同工酶的影响：经空间处理的小麦种子酯酶、过氧化物酶的同工酶谱带空间处理的比地面对照减少。由此可见,空间处理可诱导纯合植物种子发生变异,为农作物育种创造一个新途径。