X-ray fluorescence analysis using synchrotron radiation at the photon factory

X-ray fluorescence experiments at the Photon Factory in Japan are described. An energy-dispersive X-ray fluorescence system was combined with various excitation modes, i.e., a continuum and a monochromatic excitation, which consist of a crystal monochromator or a wide band pass monochromator. These excitation modes provide a wide range of band width and photon flux of excitation beams. Minimum detection limits obtained for a thin sample were less than 0.1 ppm and 0.1 pg when there was no line interference. Advantages of using monochromatic excitation are discussed, with emphasis on the possibility of chemical state analysis. Grazing incidence X-ray fluorescence is a technique very appropriate to synchrotron radiation characteristics. Near-surface analysis and trace analysis of solution samples placed on a total reflection support were made. Future plans are discussed, including microbeam analysis, tomography, X-ray excited optical fluorescence, and applications of insertion devices (undulator and wiggler).     

Crystallinity and structure of starch using wide angle X-ray scattering

Wide angle X-ray diffraction was used to evaluate the crystalline fraction of a variety of starches, using preliminary smoothing then an iterative smoothing algorithm to estimate amorphous background scattering. This methodology was then used to determine initial crystallinity and monitor gelation and retrogradation of high amylose thermoplastic starch used to produce film. Retrogradation was monitored over a 5-day period. It was found that the starch film retrograded rapidly over the first 12 h with the film displaying both B-type crystallinity and long range amorphous ordering that were separately quantitatively calculated. Changes in starch films, including complete or partial gelatinization, retrogradation and crystallinity, were all determined through wide angle X-ray diffraction.     

Chemical state analysis of sulfur and phosphorus in biological samples by X-ray fluorescence

Double-crystal high-resolution X-ray fluorescence spectroscopy was applied to the chemical state analysis of sulfur and phosphorus in biological samples of leaves and bones. Both S²⁻ and S⁶⁺ states are present in all leaves. In plants infected with the mosaic virus, the abundance of S²⁻ state was found to be less than normal. Furthermore, the total sulfur content of leaves with the mosaic virus was less than that in normal leaves. From these results we have concluded that the mosaic virus is related to the decrease in cysteine sulfur (S²⁻), which is an essential component in amino acids. Most of the phosphorus in leaves and bones was found to be in P⁵⁺ state. A small amount of P³⁺ state, however, was also detected.     

Structural characterization of wheat starch granules differing in amylose content and functional characteristics

Small-angle X-ray scattering (SAXS) together with several complementary techniques, such as differential scanning calorimetry and X-ray diffraction, have been employed to investigate the structural features that give diverse functional properties to wheat starches (Triticum aestivum L.) within a narrow range of enriched amylose content (36–43%). For these starches, which come from a heterogeneous genetic background, SAXS analysis of duplicate samples enabled structural information to be obtained about their lamellar architecture where differences in lamellar spacing among samples were only several tenths of nanometer. The SAXS analysis of these wheat starches with increased amylose content has shown that amylose accumulates in both crystalline and amorphous parts of the lamella. Using waxy starch as a distinctive comparison with the other samples confirmed a general trend of increasing amylose content being linked with the accumulation of defects within crystalline lamellae. We conclude that amylose content directly influences the architecture of semi-crystalline lamellae, whereas thermodynamic and functional properties are brought about by the interplay of amylose content and amylopectin architecture.     

Atomic force microscopy of pea starch granules: granule architecture of wild-type parent, r and rb single mutants, and the rrb double mutant

AFM studies have been made of the internal structure of pea starch granules. The data obtained provides support for the blocklet model of starch granule structure (Carbohydr. Polym. 32 (1997) 177-191). The granules consist of hard blocklets dispersed in a softer matrix material. High-resolution images have yielded new insights into the detailed structure of growth rings within the granules. The blocklet structure is continuous throughout the granule and the growth rings originate from localised defects in blocklet production distributed around the surface of spheroidal shells within the granules. A mutation at the rb locus did not lead to significant changes in granule architecture. However, a mutation at the r locus led to loss of growth rings and changed blocklet structure. For this mutant the blocklets were distributed within a harder matrix material. This novel composite arrangement was used to explain why the granules had internal fissures and also changes in gelatinisation behaviour. It is suggested that the matrix material is the amylose component of the granule and that both amylose and amylopectin are present within the r mutant starch granules in a partially-crystalline form. Intermediate changes in granule architecture have been observed for the double mutant rrb.     

Molecular aspects of sucrose transport and its metabolism to starch during seed development in wheat: A comprehensive review

Wheat is one of the most important crops globally, and its grain is mainly used for human food, accounting for 20% of the total dietary calories. It is also used as animal feed and as a raw material for a variety of non-food and non-feed industrial products such as a feedstock for the production of bioethanol. Starch is the major constituent of a wheat grain, as a result, it is considered as a critical determinant of wheat yield and quality. The amount and composition of starch deposited in wheat grains is controlled primarily by sucrose transport from source tissues to the grain and its conversion to starch. Therefore, elucidation of the molecular mechanisms regulating these physiological processes provides important opportunities to improve wheat starch yield and quality through biotechnological approaches. This review comprehensively discusses the current understanding of the molecular aspects of sucrose transport and sucrose-to-starch metabolism in wheat grains. It also highlights the advances and prospects of starch biotechnology in wheat.     

Partial substitution of organic nitrogen with synthetic nitrogen enhances rice yield,grain starch metabolism and related genes expression under the dual cropping system

Improving grain filling in the presernt farming systems is crucial where grain filling is a concern due to the extreme use of chemical fertilizers (CF). A field experiment was conducted at the experimental station of Guangxi University, China in 2019 to test the hypothesis that cattle manure (CM) and poultry manure (PM) combined with CF could improve rice grain filling rate, yield, biochemical and qualitative attributes. A total of six treatments, i.e., no fertilizer (T₁), 100% CF (T₂), 60% CM + 40% CF (T₃), 30% CM + 70% CF (T₄), 60% PM + 40% CF (T₅), and 30% PM + 70% CF (T₆) were used in this study. Results showed that the combined treatment T₆increased starch metabolizing enzymes activity (SMEs), such as ADP-glucose phosphorylase (ADGPase) by 8 and 12%, soluble starch synthase (SSS) by 7 and 10%, granule bound starch synthesis (GBSS) by 7 and 9%, and starch branching enzyme (SBE) by 14 and 21% in the early and late seasons, respectively, compared with T₂. Similarly, higher rice grain yield, grain filling rate, starch, and amylose content were also recorded in combined treatments. In terms of seasons, higher activity of SMEs , grain starch, and amylose content was noted in the late-season compared to the early season. The increment in these traits was mainly attributed to a lower temperature in the late season during the grain filling period. Furthermore, our results suggested that an increment in starch accumulation and grain filling rate were mainly associated with the enhanced sink capacity by regulating key enzyme activities involved in Suc-to-starch conversion. In-addition, RT-qPCR analysis showed higher expression levels of AGPS2b, SSS1, GBSS1, and GBSE11b genes, which resultantly increased the activities of SMEs during the grain filling period under combined treatments. Linear regression analysis revealed that the activity of ADGPase, SSS, GBSS, and SBE were highly positively correlated with starch and amylose accumulation. Thus, we concluded that a combination of 30% N from PM or CM with 70% N from CF is a promising option in terms of improving rice grain yield and quality. Our study provides a sustainable fertilizer management strategy to enhance rice grain yield and quality at the lowest environmental cost.