Showing papers on "Endosperm published in 1975"

Morphology and chemical composition of barley endosperm cell walls

Abstract: Cell walls have been isolated from barley endosperm and found to contain a microfibrillar phase which is embedded in an amorphous matrix. The microfibrillar phase probably consists of cellulose, together with tightly bound arabinoxylan and polysaccharides rich in mannose. The matrix material is arabinoxylan (approx. 25%) and β-glucan (approx. 75%). Pectic polysaccharides are absent from the isolated cell walls. After successive removal of the matrix polysaccharides with water and 1-M NaOH, only 6% of the wall remains. The intra-cellular surfaces of the wall fragments are extensively pitted, probably as a result of adpression of starch granules into the cell wall material during endosperm development. Although polysaccharides are the major components of the cell walls, some nitrogen (less than 1%) is present. Phenolic compounds may also be wall constituents, but hydroxyproline could not be detected.

Seed and Pod Wall Development in Pisum sativum, L. in Relation to Extracted and Applied Hormones

Abstract: Developing fruits of Pisurn sativum, L., cv. 'Alaska', contain relatively large amounts of hor mones, mainly concentrated in the embryos and liquid endosperm. A close relationship can be demonstrated between changes in extractable amounts of gibberellins (mainly GA20), auxins (methyl 4-chloroindol-3yl acetate and probably 4-chloroindol-3yl acetic acid), and abscisic acid, and changes in growth rates of both the pod wall and seeds. Growth of the pod wall appears to depend largely on hormones supplied by the seeds. Marked changes in the germination capacity of the maturing seeds are closely associated with changes in extractable amounts of methyl-4-chloroindol-3yl acetate and abscisic acid. It is believed that high concentrations of these substances in the embryo, rather than any restriction imposed by the testa, may prevent precocious germination of the seeds.

Genetic Control of Endosperm Amylase Activity and Gibberellic Acid Responses in Standard-Height and Short-Statured Wheats

Abstract: In contrast to standard-height wheat genotypes, short-statured wheats having major genes for dwarfness do not show increased seedling growth after treatment with gibberellic acid. Endogenous gibberellic acid induces synthesis of amylase in the endosperm of germinating seeds, but the amount of amylase synthesized is greatly increased by exogenous gibberellic acid treatment in standard-height and in short-statured wheats that have dwarfing genes from the variety “Norin 10.” “D6899,” which has the “Tom Thumb” gene for height reduction, had about one-fourth of the amylase activity of standard-height and Norin 10-derived, short-statured wheats. This genotype showed little or no increased amylase activity after gibberellic acid treatment. Genetic analyses showed that the amount of amylase synthesized was controlled by a single gene and was dependent on the number of copies of the structural gene present in the endosperm. Dwarfism in wheat may be related to a blockage in gibberellic acid utilization because other workers have found that the amount of endogenous amylase synthesized in Norin 10-derived, short-statured wheats is not growth-limiting, but it is not known if low amylase synthesis is related to dwarfism in the Tom Thumb derivative. No recombinants were recovered in a small population, suggesting that the Tom Thumb gene may pleiotropically affect plant height and the lack of response to gibberellic acid in amylase synthesis and seedling growth.

Early seed development in the Triticeae

Abstract: The rates of early seed development were compared in several species in the Triticeae which play a major role in human nutrition, and in several related genotypes whose reproductive development is of current interest to plant breeders. Embryo and endosperm development during the first five days after pollination was studied in plants of 22 genotypes grown at 20 °C with continuous light. Spikes were emasculated before anther dehiscence and then pollinated once full female receptivity was reached. The numbers of embryo and endosperm nuclei or cells in individual florets were ascertained by using large samples of fertilized florets fixed at various known times after pollination. The pattern of early seed development was essentially the same in wheat, rye, Triticale and barley, although some interspecific variation in the rate between genotypes was noted. Fertilization occurred in some florets of several genotypes studied within 40-60 min after pollination. Mitosis in the primary endosperm nucleus was completed about 6-7 h after pollination. During the next 24-48 h the number of endosperm nuclei increased geometrically, doubling about every 4-5 h. The endosperm was coenocytic at first but usually at about 72 h after pollination it became cellular. The rate of nuclear development in the endosperm declined on each successive day, the greatest fall occurring at the time of cell wall formation. Mitosis in the zygote occurred about 18-30 h after pollination which was later than mitosis in the primary endosperm nucleus. The cell cycle time in the embryo varied between species from about 12 to 18 h, and was similar to its duration in cells of other meristematic tissues in the same species. Cell cycle time in the embryo remained fairly constant during the first 5 days of seed development unlike the rate of nuclear development in the endosperm. Thus, at first the rate of embryo cell development was very slow compared with that of the endosperm nuclei, however, by the end of the fifth day the cell cycle time in the endosperm had increased to become equal to or longer than that of the cell cycle in embryo cells. The nature and possible cause (s) of rapid nuclear development in coenocytic endosperm is discussed. While embryo volume increased steadily over the period studied, the mean volume of embryo cells decreased about tenfold. This was because at first the rate of increase in embryo volume was lower than the rate of increase in embryo cell number. Eventually these two rates became similar and thereafter further development gave rise to embryo cells whose volume was constant and roughly equivalent to that of other meristematic cells in the same species. The rates of embryo and endosperm development were as a rule much faster in wheat species than in rye. By comparison, the rates in hexaploid Triticale genotypes were usually much slower than in wheat, and sometimes even slower than in rye. Results for wheat-rye chromosome addition lines, disomic for each rye chromosome, show that most rye chromosomes apparently had a pronounced effect on slowing both embryo and endosperm development. Indeed, rye chromosomes VI and V II apparently had an effect equal to that of the presence of a whole rye genome. Comparison of the maximum rates of endosperm development in diploid and related polyploid species shows that there was no effect of polyploidy during the first 48 h of the coenocytic phase of endosperm development. Concurrently, during development of the cellular embryo there was a clear effect of ploidy level, with a positive relation between ploidy level and developmental rate. These results are compared with the effects of polyploidy on the rate of development in other tissues in the same species. The rates of embryo and endosperm development in Hordeum vulgare were much faster than in diploid H. bulbosum . This result is discussed with reference to the mechanism of chromosome elimination from embryo and endosperm tissues of Fj-hybrids between these two species. The present results provide a detailed picture of the course of normal early seed development in a wide range of cereal genotypes which varied with respect to several characters known to affect rate of development in other tissues. They provide, therefore, a baseline for comparative studies which aim both to describe abnormal early seed development and to quantify its extent, in for instance Triticale withshrivelled grain. At the same time they provide some indication of the factors which apparently influence or control the rate and extent of early embryo and endosperm development in these important crop species.

The nature and genetic control of gibberellin insensitivity in dwarf wheat grain

Abstract: Eight dwarf and semi-dwarf varieties, covering a range of genetic sources of dwarfism, and four tall varieties of wheat were tested for their response to a range of GA concentrations by release of the enzyme α-amylase. The two dwarfs, Minister Dwarf and Tom Thumb, were found to be insensitive compared with the remaining 10 varieties; among the latter, differences in minimum levels of sensitivity were found that were unrelated to height phenotype. Transplant experiments, in which embryos of one genotype were grown on the endosperm of another, showed that the lack of response was a function only of the endosperm tissue and that GA release from the embryos of insensitive varieties during germination was similar to that of sensitive genotypes. The close relationship between coleoptile length and endosperm GA-insensitivity indicated that this character was controlled by the Gai 3 locus previously located on chromosome 4A. In some crosses the character displayed a pattern of inheritance that would be expected in a triploid tissue for a single gene. However in crosses of varieties carrying Gai 3 with Norin 10-Brevor 14, which has a GA-sensitive endosperm, a more complex inheritance was found, indicating that Norin 10-Brevor 14 also carried a gene or genes which can increase GA-insensitivity.

Characterization of adenosine diphosphate glucose pyrophosphorylases from developing maize seeds.

Abstract: Electrophoretic examination of 22-day-old, normal maize (Zea mays L.) endosperm extracts revealed two zones of adenosine diphosphate glucose pyrophosphorylase activity. The enzymes are identical in terms of Km for glucose 1-phosphate and the effect of 3-phosphoglyceric acid on apparent Km for glucose 1-phosphate. Both enzymatic activities increase with increasing doses of the functional alleles at the shrunken-2 and brittle-2 loci. Molecular weight differences between the two electrophoretic species were inferred from sucrose gradient centrifugation. It is suggested that the two bands of activity represent different aggregation states of the same enzyme because under different extraction conditions, only one enzyme is found. Molecular weight estimates of 237,000 and 253,000 were obtained for the smaller enzyme. It is suggested that this enzyme is an aggregate of several subunits. Comparison of the embryo and endosperm pyrophosphorylases showed the embryo activity to be more heat stable and probably independent of direct shrunken-2 or brittle-2 control.

Enzyme to break down lettuce endosperm cell wall during gibberellin-and light-induced germination

Abstract: THE physiology of lettuce seed germination has been a subject of extensive study, but very little is known of the fundamental biochemical events which occur during germination. Here we report that the endosperm cell wall is largely composed of a mannose polymer (that is, a man-nan); and that germinating seeds produce an enzyme capable of its breakdown.

Induction of hormone sensitivity by dehydration is one positive role for drying in cereal seed

Abstract: THE hydrolysis of food reserves in seeds (usually fats, starch and protein) is closely linked to embryo growth since it does not begin until germination has started. The control of food mobilisation by the embryo is best understood in cereals such as barley and wheat. In these cases the hormone gibberellin, moving from the embryo, activates the aleurone layer to produce an array of hydrolytic enzymes, including α-amylase, protease and β-1,3-glucanase and to secrete them into the endosperm where stored materials are located1. The stored food is of course laid down in the grain during its development on the mother plant. But at the time when this accumulation is taking place the grains contain relatively high levels of gibberellin2; nevertheless, the food reserves seem free from hydrolytic attack. One possible reason for this is that in undried grains on the mother plant the hormonal control system for enzyme synthesis and secretion does not function. No research has been done directly on this problem; what relevant research there is shows some discrepancies3,4. Our results, described here, demonstrate that the hormonal control system operates fully only after the mature grains have been dried. Dehydration is necessary for the development of complete sensitivity to gibberellin.

Factors Regulating the Accumulation of Starch in Ripening Wheat Grain

Abstract: 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.

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

Abstract: 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.

Movement of 14C-labeled Sugars into Kernels of Wheat (Triticum aestivum L.)

Abstract: An anatomical study of wheat (Triticum aestivum L.) kernels 14 days after anthesis revealed that the tracheary elements of the pericarp vascular bundle are not in direct continuity with those of the rachilla. The phloem was continuous from the rachilla into the crease of the pericarp.Shortly after exposure of the flag leaf to (14)CO(2), relatively high proportion of the (14)C extracted from the pericarp and endosperm was found in glucose and fructose. With additional time, the percentage of (14)C in the monosaccharides declined and that in sucrose increased to a maximum 3 hours after (14)CO(2) exposure. The monosaccharides comprised about one-half of the soluble sugars extracted from the pericarp. Based on these observations, it appeared that sucrose hydrolysis might be prerequisite to sugar movement from the terminal phloem elements in the pericarp and into the endosperm. However, when (14)C-fructosyl-sucrose was injected into the peduncle, there was little additional randomization of the (14)C between the glucose and fructose moieties of sucrose extracted from the pericarp and endosperm compared to the rachis sucrose. If we assume that injected sucose was transported to the kernels via the phloem, then either sucrose moves out of the terminal phloem elements in the pericarp and into the endosperm unaltered, or if hydrolysis and resynthesis are a prerequisite to transport into the endosperm, the products of hydrolysis are not freely available for isomerization.

The breakdown of lipid reserves in the endosperm of germinating castor beans.

Abstract: 1. Lipid extracts were obtained from castor-bean endosperm tissue at various times during germination and, after purification, the total lipid content was determined. Quantitative measurements of the triglyceride and phospholipid content together with the fatty acid composition were made. 2. The total lipid content of the endosperm rapidly decreased during germination; after 10 days less than 20% of the original weight of lipid remained. In contrast, the phospholipid content (initially less than 0.5% of the total lipid) increased slightly during this time. The fatty acid composition and the relative proportions of the triglyceride species of the total lipid extract remained constant during 10 days of germination. 3. Gibberellic acid (0.3 mM) markedly stimulated the rate of lipid breakdown but did not alter either the fatty acid composition or the relative proportion of triglyceride species. 4. The embryo had little effect on lipid metabolism in the endosperm tissue; only after 6 days of germination were differences observed in the rate of fat utilization in the presence and absence of the embryo.

The induction of enzyme activity in the endosperm of germinating castor-bean seeds.

Abstract: 1. Endosperm extracts were prepared at various times during germination from intact castor-bean seeds and from seeds from which the embryos had been removed. The sterilized seeds were incubated either on solid water agar or on agar containing 0.3 mM-gibberellic acid. 2. Isocitrate lyase and 3-hydroxyacyl-CoA dehydrogenase had very low activities in the mature seeds, but increased 44-fold and 27-fold respectively during germination. In contrast, the extracts of mature seeds had considerable acid and alkaline lipase activity and this only increased two- to three-fold during the incubation period. 3. Incubation of the seeds with gibberellic acid accelerated the rate of appearance of isocitrate lyase and 3-hydroxyacyl-CoA dehydrogenase. It also increased the total activity attained. However, the application of hormone had, in comparison, little effect on the development of lipase activity. 4. The removal of the embryo had little influence on the development of enzyme activity in the endosperm tissue; only with isocitrate lyase was a decrease in activity observed in the absence of the embryo.

Chromosomal control of non-gliadin proteins from the 70% ethanol extract of wheat endosperm

Abstract: The non-gliadin fraction of the 70% ethanol extracts of compensated nulli-tetrasomics and ditelosomics of Triticum aestivum cv. Chinese Spring has been analyzed by combined electrofocusing and electrophoresis. Seventeen of the 21 protein map components of the euploid have been ascribed to eight chromosomes: 4Aβ, 3BS, 6BS, 7BS, 3Dβ, 4D, 5D and 7DS. The relationship of the different map components with other proteins previously associated with the same chromosomes is discussed.

A rapid guide to endosperm malting potential of barleys using a sedimentation procedure

Abstract: A rapid (10 minute) procedure is described which appears to differentiate barleys having good potential for malting by traditional methods from those less easy to malt. During controlled milling, barleys of good malting potential release more starch granules and, as a result, a suspension of the milled grain sediments more slowly in 70% ethanol. This probably reflects differences in the nature of the endosperm cell wall and the starch-protein matrix.

Studies on White-Belly Rice Kernel : IV. Opaque rice endosperm viewed with a scanning electron microscope

Abstract: These studies in series were devoted to clarify the characteristics of the white belly kernel which had an opaque part at the ventral portion of its endosperm. In this experiment, white belly kernels were cut transversely with a razor blade and scanning electronic photographs were taken. The experimental materials used were Norin-8, Kinmaze, Sekai-1, Gohyakumangoku (white core rice) and Sinthurumochi (glutinous rice) of Japonica type variety and Keikyakusen and Kouketuzu (glutinous rice) of Indica type variety. The following results were obtained. 1. The translucent parts of endosperm tissue of white belly kernels were easily pervious to light, but the opaque parts of endosperm tissue of these kernels were difficult to transmit light (fig. 3, 6). The permeability of light in the individual endosperm cell varied from opaque parts to translucent parts (fig. 4, 8). 2. The compound starch granules in translucent parts of white belly kernel endosperm were polygonal in shape and tightly packed with no air spaces among them (fig. 12), whereas those in opaque part of this endosperm were round in shape and loosely packed with many intergranular air spaces (fig. 10, 13, 15, 23). 3. The compound starch granules, which located the outerside of opaque parts, were easily broken into many single starch granules by the mechanical stress (fig. 15-16). 4. The opaque parts of white core, milky white, and opaque kernels had round in shape, loosely packed compound starch granules resembled with those of white belly kernels (fig. 19-22). 5. The glutinous rice had micropores on the inside surface of the single starch granules and hollows on the outer surface of compound granules, which were absent in non-glutinous rice starch granules (fig. 25-27). 6. The endosperm cells in 5-day old kernels had uniform round compound starch granules which were loosely filled with many air spaces (fig. 28-29). The endosperm cells in 16-day old kernels were packed by compound starch granules which were varied in shape and size (fig. 30-32). In more developing kernels, the compound starch granules were tightly packed in the endosperm cell and no air space was observed among the granules. Then, the endosperm tissue became translucence ( fig. 33). 7. The starch granules of endosperm had two types, i. e., one was the large compound starch granule which was composed of many single starch granules and another was the small compound starch granules which were composed of several single starch granules. Among the compound starch granules, the globular protein body were embedded (fig. 37). 8. From these results, because of the loose structure and the high proportion of inter-granular air spaces, the opaqueness of endosperm tissue would be caused by light scattering.

Evidence that phosphatidylcholine and phosphatidylethanolamine are synthesized by a single enzyme present in the endoplasmic reticulum of castor-bean endosperm.

Abstract: Increasing concentrations of CDP-choline progressively inhibit the measured incorporation of CDP-[2-14C]ethanolamine into phosphatidylethanolamine catalysed by the ethanolaminephosphotransferase present in endoplasmic-reticulum membranes isolated from castor-bean endosperm cells. This inhibition parallels that observed during CDP-[Me-14C]choline incorporation and suggests that a single enzyme utilizes both these substrates.

Activities of Two Peptidases in Resting and Germinating Seeds of Scots Pine, Pinus sylvestris

Abstract: Extracts prepared from resting seeds of Scots pine, Pinus sylvestris L., rapidly hydrolysed two peptides, Leu–Tyr and Ala–Gly, at pH 8.6 and 7.8, respectively. In gel chromatography on Sephadex G-100 the two activities were eluted as separate peaks, which indicates that they are due to two different peptidases. The seeds were allowed to germinate at 20°C, the activities of the two enzymes were assayed separately on extracts from the endosperm and seedling tissues at different stages of germination, and compared with corresponding changes in dry weight and total nitrogen. Both enzyme activities were relatively high in the endosperm of resting seeds, and they increased about 2- and 3-fold during germination (expressed as enzyme units per seed), the increases coinciding with the time of rapid reserve protein mobilization. Both enzymes were also abundant in the embryos of resting seeds, and during germination their activities increased even more rapidly than those in the endosperm. The possible role of these two “alkaline peptidases” in reserve protein hydrolysis is discussed.

Localization and Properties of Ribulose Diphosphate Carboxylase from Castor Bean Endosperm

Abstract: A substantial portion of the ribulose 1,5-diphosphate carboxylase activity in the endosperm of germinating castor beans (Ricinus communis var. Hale) is recovered in the proplastid fraction. The partially purified enzyme shows homology with the enzyme from spinach (Spinacia oleracea) leaves, as evidenced by its reaction against antibodies to the native spinach enzyme and to its catalytic subunit. The enzyme from the endosperm of castor beans has a molecular weight of about 500,000 and, with the exception of a higher affinity for ribulose 1,5-diphosphate, has similar kinetic properties to the spinach enzyme. The castor bean carboxylase is inhibited by oxygen and also displays ribulose 1,5-diphosphate oxygenase activity with an optimum at pH 7.5.

DISTRIBUTION OF α-AMYLASE IN THE TRITICALE KERNEL DURING DEVELOPMENT

Abstract: Seed of four triticale (Triticale hexaploide Lart.) cultivars, two wheat (Triticum aestivum L.) cultivars, and one rye (Secale cereale L.) cultivar were harvested at 4-day intervals from 6 to 42 days post-anthesis. Alpha-amylase activity was determined in the embryo, pericarp, aleurone, and endosperm of the seed. In all cases, the α-amylase activity in the embryo was low. The pericarp activity reached a maximum in all samples at approximately 10–15 days post-anthesis. Aleurone and endosperm activity remained low throughout the development period in all but one triticale cultivar. In triticale cultivar 6A 190, the aleurone and endosperm α-amylase activity remained low until approximately 20–25 days post-anthesis, at which point the activity increased to levels normally associated with sprouted grain. Light microscopic examination of the 6A 190 at 10 days post-anthesis showed that the starch in the inner portion of the pericarp was digested. At 22 days, all pericarp starch had disappeared. Specific lesions ...