Factors Regulating the Accumulation of Starch in Ripening Wheat Grain

1975 ◽  
Vol 2 (3) ◽  
pp. 311 ◽  
Author(s):  
CF Jenner ◽  
AJ Rathjen
Keyword(s):  
Free Space ◽  
Radioactive Material ◽  
Wheat Grain ◽  
Wheat Endosperm ◽  
Insoluble Material ◽  
Days After Anthesis

Estimates of the faculty of wheat endosperm to convert sucrose to starch were obtained by incubating dissected endosperm in solutions of [14C]sucrose and then measuring the absorption of [14C]sucrose and the amounts of 14C accumulating as insoluble material. Samples of grain were taken from plants growing in the field at each of four stages of maturity: at 17 days after anthesis, just after the synthesis of starch had begun; at 28 days when the grains were about half-grown; at 38 days when the accumulation of starch had slowed down and almost ceased; and at 49 days when the grains were fully grown. More [14C]sugar entered the free space of the endosperm of 49- than of 28-day-old grain, and more sucrose was absorbed by the endosperm cells of the older grain. Endosperm taken from grains sampled at 28 days produced more insoluble radioactive material (mostly starch) than grains sampled at any other stage, and compared to 28-day grain, grain sampled at 38 days produced less than one-third of the quantity of [14C]starch. At each stage, the amounts of sucrose in the free space and in the cells of the endosperm were determined on comparable samples of grain developing normally in the field. There was significantly more sucrose on day 38 than on day 28, both in the free space and in the cells of the endosperm. It is concluded that the onset of the declining phase of accumulation of starch, as the grains begin to ripen, is due to a fall in the capacity of the grains to synthesize starch, and is not attributable to postulated reductions in the supply of assimilate to ripening grain.

Thermal Characteristics of Soluble Starch Synthase From Wheat Endosperm

1995 ◽  
Vol 22 (4) ◽  
pp. 703 ◽  
Author(s):  
CF Jenner ◽  
K Denyer ◽  
J Guerin
Keyword(s):  
Thermal Characteristics ◽  
Soluble Starch ◽  
Starch Synthase ◽  
Wheat Grain ◽  
Wheat Endosperm ◽  
Temperature Range ◽  
Higher Temperature ◽  
Temperature Responses

The aim of the work reported in this paper was to characterise the thermal responses of soluble starch synthase (SSS) extracted from the endosperm of the developing wheat grain. Using partially purified preparations of SSS, the reaction obeyed Michaelis-Menten kinetics with both substrates amylopectin and ADPglucose. Both the Vmax and the Km varied with temperature. Values for Vmax were higher at 45�C compared with 25�C. However, the Km values for both substrates were also higher at 45�C than at 25�C indicating that the affinity of the enzyme for its substrates was reduced at the higher temperature. Over the temperature range 15-45�C, the Km for arnylopectin was minimal at 20�C, and rose exponentially between 25 and 45�C. Kinetic analyses indicated that the reaction was sequential and that the substrates could bind to the enzyme in either order. At 25�C the binding of one substrate to the enzyme increased the affinity of the complex for the second substrate but at 45�C these effects were abolished. These thermal characteristics of SSS could explain certain important features of the temperature responses of starch deposition in the wheat grain in vivo.

Effects of Shading or Removing Spikelets in Wheat: Testing Assumptions.

1980 ◽  
Vol 7 (2) ◽  
pp. 113 ◽  
Author(s):  
CF Jenner
Keyword(s):  
Nitrogen Content ◽  
Grain Growth ◽  
Dry Matter ◽  
Cereal Grains ◽  
Physiological Processes ◽  
Amino Compounds ◽  
Insoluble Material ◽  
Cereal Grain ◽  
Days After Anthesis

Shading for 10 days reduces the supply of sucrose available for distribution to the grains, and the amounts of sucrose in the endosperm, but has no effect on the delivery of soluble amino compounds to the grain. Soon after returning shaded plants to full illumination, the supply of sucrose to the ear is restored to unshaded levels. In addition, shading affects the amounts of ethanol-insoluble material in the peduncle and the rachis, and the nitrogen content of this material in the peduncle. Trimming ears to four spikelets (10 days after anthesis) results in an increased supply of sucrose and soluble amino compounds available for distribution to the remaining grains. More nitrogen enters the grains of trimmed ears than intact ones, but inflow of sucrose is not increased by trimming the ear, and no more starch is deposited in grains developing in trimmed ears. While the responses to shading observed in this work indicate that the interpretation of the effects of shading on the growth of cereal grains may not be straightforward, the use of shading as a treatment for investigating physiological processes such as grain growth is not disqualified. However, as removing spikelets results in several unpredicted, and inexplicable, responses in the grain itself, the value of such a treatment as a means of investigating mechanisms regulating the accumulation of dry matter in the cereal grain is questionable.

Water Relations of the Developing Wheat Grain

1980 ◽  
Vol 7 (5) ◽  
pp. 519 ◽  
Author(s):  
EWR Barlow ◽  
JW Lee ◽  
R Munns ◽  
MG Smart
Keyword(s):  
Water Deficit ◽  
Flag Leaf ◽  
Maximum Level ◽  
Grain Filling ◽  
Controlled Environment ◽  
Wheat Grain ◽  
Grain Filling Period ◽  
Pigment Strand ◽  
Days After Anthesis ◽  
Wheat Spike

The physiological and anatomical mechanisms underlying the reduced sensitivity of wheat grain growth to water deficits in the post anthesis period have been investigated. The water potential (Ψ) and water content of the developing wheat grain and of other tissues within the wheat spike and flag leaf were compared under controlled environment and field conditions. In the 14 days following anthesis when the amount of water in each grain was increasing, the Ψ gradient between the grain and the rest of the plant was most pronounced. This Ψ gradient disappeared when the water per grain reached its maximum level (15 days after anthesis). The apparent turgor potential (P) of the wheat grain was very small (less than 0.2 MPa) throughout the grain filling period. When water was withheld 10 and 20 days after anthesis, the grain Ψ changed little despite a large decrease in the Ψ of the glumes, rachis and flag leaf. Grain Ψ showed the same independence during a diurnal cycle of water deficit. The independence of grain Ψ under water deficit conditions may be related initially to the xylem discontinuity in the floral axis and, in longer-term water stress situations, to the deposition of lipid in the pigment strand of the grain itself.

Physiological Basis of Genetic Differences in the Growth of Grains of Six Varieties of Wheat

1978 ◽  
Vol 5 (3) ◽  
pp. 249 ◽  
Author(s):  
CF Jenner ◽  
AJ Rathjen
Keyword(s):  
Genetic Variation ◽  
Dry Matter ◽  
Kinetic Properties ◽  
Wheat Grain ◽  
Physiological Basis ◽  
Rate Of Growth ◽  
Insoluble Material ◽  
Two Parameters ◽  
The Relationship ◽  
Rate Of Accumulation

The physiological basis of genetic variation in rate of accumulation of dry matter (growth) in wheat grain has been investigated by culturing ears of six different varieties on solutions of sucrose. Differences between varieties in accumulation of dry matter in the cultured ears were similar to those for grains growing in the field. Intracellular concentration of sucrose was positively correlated with increases in dry matter in treatments within varieties, but was not related to differences between varieties. In comparisons between varieties, high intracellular levels of sucrose were more often associated with low rates of accumulation of dry matter than with high rates. It is concluded that, within the varieties investigated here, genetic variation in the rate of deposition of dry matter in the endosperm is not attributable to variation in supply of assimilate to the grain. No single or simple parameter of the growth of the grain at anthesis, or in the succeeding 2 weeks, was related to the grain's subsequent rate of growth. The weight of ethanol-insoluble material in the endosperm itself at day 19 was not indicative of the amounts of this fraction deposited in the endosperm in the week that followed day 19. Significant variation between the varieties was observed in the relationship (viz. the slope) between the intracellular amounts of sucrose and the rate of accumulation of ethanol-insoluble dry matter (mostly starch), a relationship which is presumed to reflect kinetic properties of the process(es) converting sucrose to starch. In the six varieties investigated, all the observed differences in grain growth rate could be attributed to variation in the slope defined above, and/or in day 19 endosperm dry matter. It is suggested that these two parameters reflect two independent physiological determinants, accounting for much of the genetic variation in the rate of growth of wheat grain.

Ultrastructure of the cuticular membranes of the developing wheat grain

1975 ◽  
Vol 53 (18) ◽  
pp. 2077-2087 ◽  
Author(s):  
I. N. Morrison
Keyword(s):  
Triticum Aestivum ◽  
Outer Layer ◽  
Outer Integument ◽  
Triticum Aestivum L ◽  
Ultrastructural Level ◽  
Ultrastructural Changes ◽  
Grain Development ◽  
Wheat Grain ◽  
Maximum Thickness ◽  
Days After Anthesis

The distribution of cuticular membranes within the mature wheat ovule (Triticum aestivum L. cv. Heron) and the subsequent changes in these layers during grain development were investigated at the ultrastructural level. At anthesis, the inner epidermis of the pericarp and the outer integument are separated by two, thin, osmiophilic, cuticle-like lamellae. Similar osmiophilic boundaries, also double in nature, are evident between the outer and inner integuments and between the inner integument and the nucellar epidermis. By 7 days after anthesis, only the outer layer of cells of the inner integument and the nucellar epidermis are bounded by cuticularized layers, which, by this time, are recognizable as the developing outer and inner cuticles, respectively, of the mature caryopsis. Between 7 and 14 days after anthesis, the outer cuticle assumes a highly reticulate appearance in section and is delineated on the outside by a cutin layer, 90–120 nm in thickness. By 17 days both the outer and inner cuticles have attained maximum thickness, varying from 3.0 to 3.6 μm and 0.8 to 1.1 μm, respectively. Unlike the outer cuticle, the inner cuticle has no distinct internal substructure. The two are closely appressed by 4 weeks after anthesis and show no further ultrastructural changes.

Effects of Sulfur Deficiency on the Synthesis and Accumulation of Proteins in the Developing Wheat Seed

1987 ◽  
Vol 14 (5) ◽  
pp. 503 ◽  
Author(s):  
SL Castle ◽  
PJ Randall
Keyword(s):  
Protein Synthesis ◽  
Storage Protein ◽  
Gel Electrophoresis ◽  
Polyacrylamide Gel Electrophoresis ◽  
Sodium Dodecyl ◽  
Polyacrylamide Gel ◽  
Wheat Seed ◽  
Wheat Grain ◽  
Sulfur Deficiency ◽  
Days After Anthesis

The effects of sulfur deficiency on the synthesis and accumulation of polypeptides in the developing wheat grain between 6 and 36 days after anthesis were examined by sodium dodecyl sul- fate-polyacrylamide gel electrophoresis. Wheat grain proteins were divided into two groups based on their solubility characteristics: (a) salt-soluble, and (b) salt-insoluble. Sulfur deficiency resulted in changes in the synthesis and accumulation of both groups of polypeptides, but the changes were more pronounced in the salt-insoluble group. In neither case were the changes as dramatic as those reported previously for sulfur deficient legume and barley seeds. In sulfur-deficient wheat plants, storage protein synthesis in developing seeds was detectable earlier than in plants grown with adequate sulfur.

Early Stages in the Development of Wheat Endosperm. I. The Change From Free Nuclear to Cellular Endosperm

1975 ◽  
Vol 23 (2) ◽  
pp. 311 ◽  
Author(s):  
DJ Mares ◽  
K Norstog ◽  
BA Stone
Keyword(s):  
Mitotic Spindle ◽  
Endosperm Development ◽  
Wall Material ◽  
Ventral Region ◽  
Wheat Endosperm ◽  
Cellular Endosperm ◽  
Dorsal Area ◽  
Cytological Features ◽  
Ventral Area ◽  
Days After Anthesis

The cytological features of the cellularization of the free nuclear endosperm of wheat are described. Following the initial proliferation of nuclei the endosperm is divided into a small ventral area and a larger dorsal area which then develop separately. Cell wall formation in both regions is independent of a mitotic spindle and appears to be mediated by freely growing walls. Wall material is laid down along lines already marked out by ingrowth from the plasma membrane into the central cell cyto- plasm. By the time that cellularization is complete the smaller ventral region has been transformed into a layer of small, thick-walled cells whilst the larger dorsal area contains large, highly vacuolate endosperm cells. A model is proposed which endeavours to link the morphological features observed in embryo sacs, collected from wheat ovules 2-6 days after anthesis, into an ontogenetic sequence. This model is compared with previously published descriptions of wheat endosperm development.

Pattern of endoproteolysis following wheat grain germination

1995 ◽  
Vol 95 (2) ◽  
pp. 253-259 ◽  
Author(s):  
Fernando Dominguez ◽  
Francisco J. Cejudo
Keyword(s):  
Wheat Grain

Bovine Platelet Proteins II. Purification of Platelet Fibrinogen

1969 ◽  
Vol 21 (03) ◽  
pp. 419-427 ◽  
Author(s):  
N. O Solum ◽  
S Łopaciuk
Keyword(s):  
Analytical Ultracentrifugation ◽  
Insoluble Fraction ◽  
Disc Electrophoresis ◽  
Plasma Fibrinogen ◽  
Starch Gel Electrophoresis ◽  
Freezing And Thawing ◽  
Insoluble Material ◽  
High Resolution Power ◽  
Starch Gel ◽  
Platelet Proteins

Summary1. Platelet fibrinogen has been purified from washed bovine platelets. The procedure was based on the methods for purification of plasma fibrinogen by fractionated precipitations and extractions with ethanol and glycine below 0°, and precipitation of proteins by dimethylformamide at 0°.2. The platelet extract obtained by freezing and thawing of the cells, freed from insoluble material by centrifugation at 23,000 x g for 30 min, contained 0.22 ±0.003mg fibrinogen per 109 platelets. Total protein of this fraction was 0.77 ±0.08 mg per 109 platelets whereas that of the insoluble fraction was 0.79 ±0.09 mg per 109 platelets.3. The most purified platelet fibrinogen fraction contained 91-98% of the protein in a thrombin-clottable state. The yield was approx. 20%. It showed homogeneity in analytical ultracentrifugation, in immunoelectrophoresis using an antiserum produced by immunization of rabbits against platelet extract, and in starch gel electrophoresis using a discontinuous system of Tris HCl and borate buffers offering a high resolution power towards the platelet proteins. Polyacrylamide disc electrophoresis revealed two to three faint lines behind the main fibrinogen line. At least one such line was also observed with purified plasma fibrinogen.

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