Segmental mobility of polymers in starch granules at low moisture contents

The objective of this study was to determine the moisture content at which the segmental mobility of polymers within a starch granule is restricted. Common corn, waxy corn and high amylose corn starch samples were equilibrated to a final water activity of 0.15, 0.33, 0.75 or 0.97. The samples were then exposed to iodine vapor for 24 h and the color, absorption spectra and X-ray diffraction patterns were measured. Stained and unstained granules were also viewed under a bright field and polarized light microscope. The results demonstrate that successive local transitions occur within a granule with increasing moisture contents. Furthermore, the data shows that at moisture contents of about 13%, iodine is able to penetrate the granule and the resulting complex disrupts the crystalline arrangement within the granules. The differences in extent of mobility of polymers between different starch types can potentially illuminate differences in starch structure and architecture.     

Phosphorylase activity in relation to starch synthesis in developing Hordeum distichum grain

Activity, control and primer requirements of starch phosphorylase in developing barley endosperm were investigated. Phosphorylase was detected in endosperm extracts from 3 days after anthesis. Unprimed activity was predominant between 2 and 10 days after anthesis, when it constituted 70–80% of total activity, but this proportion declined rapidly as the grain developed. The existence of at least 2 isoenzymes was indicated by studies of pH dependence and phosphate inhibition, and was further supported by acrylamide gel electrophoresis and column chromatography using DEAE-cellulose. The two isoenzymes which ere possibly both glyco proteins, appear in barley endosperm soon after anthesis. One appears capable of unprimed activity, and may be associated with the initiation of a-1,2 glucans, which then serve as primers for starch synthetase. This disappears by 13–15 days after anthesis. The other isoenzyme is capable of some unprimed activity but undergoes modification between 15 and 20 days after anthesis, resulting in the loss of unprimed activity. The relevance of the results to initiation of starch synthesis and to starch synthetase in amyloplasts is discussed.     

Oxygen transfer deficiencies in starch-based media

Insufficient oxygen transfer in a highly viscous media with varying viscosity occurs during the degradation of starch byBacillus licheniformis. Oxygen transfer rate (OTR) decreased below 0.3 gl^–1 h^–1 for viscosities above 5 to 10 mPa.s and agitation speeds lower than 710 rev/min. Increasing agitation speeds by 30 to 50% compensated for the decrease in OTR for viscosities between 10 and 200 mPa.s. A dual impeller is considered essential for growth improvement.     

Electrophoretic types of leucine aminopeptidase in sheep serum

Leucine aminopeptidase in sheep serum was studied by starch gel electrophoresis. Two phenotypes, A and B, were observed, of which the former was present in 70–90 % of all the sheep examined. These two phenotypes have been shown to be controlled by a single autosomal locus, with two alleles Lay^A and Lap^B . The Lap^A allele is dominant. The frequencies of Lap phenotypes and alleles were determined in eleven Spanish and two foreign breeds. Serum alkaline phospatase and serum leucine aminopeptidase are electrophoretically distinct.     

Starch content of etiolated radish (Raphanus sativus L.) hypocotyls as affected by chloramphenicol and external sucrose

Abstract

Starch was enzymatically assayed in the hypocotyls of radish (Raphanus sativus L.) seedlings grown in water or chloramphenicol (CAP) 1 × 10^4. CAP inhibits starch formation and its effect is related to the concentration. Both CAP- and water-grown hypocotyls are able to accumulate starch when sucrose is supplied in the medium, thus suggesting that the damage caused by CAP to the amyloplast is not irreversible. Apical segments of both water- and CAP- grown hypocotyls accumulate starch upon incubation in sucrose solutions while basal segments are unable to accumulate starch even in the presence of sucrose. The authors suggest that the basal segments are unable to perform sucrose uptake or that the amyloplast is incapable to starch synthesis. In any case the inability of the basal segment to perform sucrose uptake is independent of CAP. These findings confirm that the radish hypocotyls is not homogeneous along its axes.     

Seasonal pattern of accumulation and effects of low temperatures on storage compounds in Trifolium repens

The seasonal pattern of concentrations of nitrogen, starch and vegetative storage protein (VSP) in stolons of Trifolium repens L. grown in the field were studied. Two different genotypes, cv. Aran and cv. Rivendel, differing in their morphology (stolon thickness and branching rate) but with similar growth rates, were used. Maximum concentrations of starch were found in summer whereas hydrolysis of starch took place throughout winter, suggesting that C storage is more important for winter survival than for promotion of early spring growth. On the other hand, VSP and nitrogen accumulated in autumn and early winter and then decreased when growth was resumed during early spring. For both cultivars, an inverse relationship was found between VSP concentration in stolons and mean air temperature, suggesting that VSP accumulation may be triggered by low temperature. Further experiments with plants grown under different regimes of temperature and daylength, suggested that VSP synthesis is stimulated by low root temperatures, with a slight synergistic effect of short daylength.
The effects of root temperature on growth, N₂ fixation, NH₄⁺ uptake and N allocation within Trifolium repens L., were studied under controlled conditions. The shoot growth rate was greatly reduced when root temperatures were lowered from 12 to 6°C, while the rate of stolon growth was less affected. Low root temperatures inhibited N2 fixation more than it did NH₄⁺ uptake, but the relative allocation of N to stolons was increased. Lowering root temperature also increased the accumulation of VSP in stolons. These results are discussed in terms of the mechanism associated with low temperature stimulation of VSP accumulation and its coupling with changes in the source/sink relations for allocation of N, between growth and storage.     

Determinants of resistant starch accumulation in wheat endosperm

A part of the big three cereal crops in the world, wheat has become a major constituent of the everyday food chain and is grown at a massive scale to meet global demands. This makes it an important crop from an economic as well as food security perspective. Selection of high-quality cultivars and consistent trait enhancement for such cultivars is crucial, and in light of new challenges from climate change, this has become an absolute necessity of time. In this regard, we conducted a detailed qualitative and quantitative trait analysis for multiple commercially viable varieties of wheat, and corresponding results were subjected to a series of critical statistical analyses. Final results have shown that five cultivars including Uqaab-2000, Faisalabad- 85, Anmol-19, NARC-2009, and Pirsabak-2004 depicts higher levels of various essential qualitative and quantitative traits (including Starch content, grain weight, RS content, Protein content, etc.) and are most viable varieties for further growth and trait enhancements to meet regional and global food challenges.