Showing papers on "Endosperm published in 1969"

Glyoxysomes of castor bean endosperm and their relation to gluconeogenesis

Abstract: Ripe seeds of the castor bean (Ricinus communis) are very rich in fat ( > 60% of the dry weight) that is contained in endosperm tissue surrounding the embryo. During germination there is a precipitous fall in the total fat content, and sugars, principally sucrose, are formed. These sugars are absorbed and utilized by the growing embryo, but during the fifth day of germination, at 30' C, when fat breakdown is at its height, a gram of sugar accumulates for each gram of fat consumed.l

Presence of ADP-Glucose Pyrophosphorylase in Shrunken-2 and Brittle-2 Mutants of Maize Endosperm.

Abstract: ADP-Glucose pyrophosphorylase activity has been detected in relatively low amounts in the embryos and endosperms of sh(2) and bt(2) mutant maize seeds. The total enzyme activities in sh(2) and bt(2) were about 12% and 17% respectively, of that found in starchy maize seeds (Dekalb 805). The ADP-glucose pyrophosphorylases from the starchy and mutant maize seeds were activated by 3-phosphoglycerate. However, the extent of the activation of the sh(2) enzyme was not as great as that observed with the bt(2) and Dekalb 805 enzymes. The low levels of ADP-glucose pyrophosphorylase activity in the maize mutants correlate well with the low levels of starch found in the endosperm of these mutants.

Enzymic Mechanism of Starch Breakdown in Germinating Rice Seeds II. Scutellum as the Site of Sucrose Synthesis.

Abstract: In a close parallel to the developmental pattern of α-amylase activity, a rapid increase of maltase activity occurred in the endosperm tissue of germinating rice seeds after about 4 days of the seed imbibition. The overall pattern of the 2 hydrolytic enzyme activities strongly suggest that amylolytic breakdown is the major metabolic route of starch utilization in the germinating rice seeds. Results of the chemical analyses of sugar constituents as well as the measurements of sucrose synthetase activity show that the scutellum is the site of sucrose synthesis in the germinating rice seeds. It is thus supported that glucose derived from the reserve starch in endosperm is transported to scutellum, where it is converted to sucrose. Sucrose is further mobilized to the growing tissues, shoots and roots.

Two Additional Phosphorylases in Developing Maize Seeds

Abstract: Two additional phosphorylases (III and IV) have been detected in developing seeds of maize. Phosphorylase IV is found only in the embryo (with scutellum). It is also present in the embryo of the germinating seed where its activity is 90-fold greater than the activity in the developing embryo 22 days after pollination. Phosphorylase IV is eluted from a DEAE-cellulose column in the same fraction as phosphorylase I of the endosperm, and the 2 enzymes are similar in many respects. Phosphorylase IV is distinguished from phosphorylase I by electrophoretic mobility, by pH optimum, and because its properties are not affected by the shrunken-4 mutation. Phosphorylase III is found both in the endosperms and embryos of developing seeds. Activity for this enzyme is not detected in crude homogenates nor eluates from a DEAE-cellulose column apparently because it complexes with a non-dialyzable, heat-labile inhibitor. High activity is found after protamine sulfate fractionation. Phosphorylase III is bound to protamine sulfate and is then removed by washing with 0.3 m phosphate buffer. Phosphorylase III activity in the endosperm is not detectable 8 days after pollination but is present 12 days after pollination. Phosphorylase III differs from phosphorylases I, II, and IV in several respects-pH optimum, pH-independent ATP inhibition, time of appearance in the endosperm, and because purine and pyrimidine nucleotides are equally inhibitory. In common with phosphorylase II, phosphorylase III apparently does not require a primer to initiate the synthesis of an amylose-like polymer.

A possible role for cyclic AMP in gibberellic acid triggered release of alpha-amylase in barley endosperm slices.

Abstract: L'adenosine monophosphate cyclique peut agir comme intermediaire dans la synthese, controlee par l'acide gibberellique, de l'α-amylase (α-1, 4-glucan-4-glucanohydrolase) dans des tranches de grains d'orge sans embryon.

The effect of the endosperm on the formation of gibberellin by barley embryos

Abstract: It has been shown that the scuttellum of germinating barley embryos synthesises gibberellin in intact grains or when detached from the endosperm, but not when attached to the endosperm if the axis is removed. Evidence is given to support the hypothesis that the inhibition of gibberellin synthesis is caused by a disturbance of sugar metabolism.

Increased endosperm modification of abraded barley grain after gibberellic acid treatment

Abstract: Physiological and structural observations on barley grains revealed that the pericarp is impermeable to exogenous gibberellic acid. The use of a mechanical hand-mill abraded the pericarp at the non-embryo (distal) end of the grain without damaging the embryo or the overlying husk. When grown in gibberellic acid, the α-amylase content of these abraded grains was significantly higher than that of the controls. Malts prepared from abraded grains were visually identical with control malts prepared with gibberellic acid, but they gave higher hot water extracts. Grain abrasion permitted exogenous gibberellic acid to reach a larger number of aleurone cells, thus increasing the extent of endosperm modification during growth.

Development of starch and other components in normal and high amylose barley

Abstract: The rate of synthesis of starch in the North American six-rowed barley Glacier (C.I. 9676) was greater than that in the high amylose cultivar designated Glacier (Pentlandfield). In both cases most of the synthetic activity in the developing grain occurred between the third and sixth weeks after anthesis, but the total starch content of Glacier (Pentlandfield) was reduced by some 6% whilst its total production of protein and fats was greater. The ratio of amylose to amylopectin in the starch of both barleys increased during ripening of the grains, but the proportion of amylose in the mature starch of Glacier (Pentlandfield) attained a value of about 47%, compared with about 26% in Glacier (C.I. 9676). The average diameter of the starch granules in the high amylose barley was smaller than in normal barley at all stages of endosperm development. The two parental varieties and ten others closely related to Glacier were examined, but none possessed the high amylose characteristic.

Isolation and chemical composition of protein bodies and matrix proteins in corn endosperm

Abstract: Microscopic examination of endosperm cells reveals the presence of starch granules and protein bodies held together by a protein matrix. To separate these subcellular structures, endosperm tissue, obtained 24 days after pollination, was gently homogenized in phosphate buffer. The particulate cell components were then separated by zone sedimentation on a sucrose density gradient. Sequential fractions were taken from different depths of the gradient tube, analysed for protein, and examined microscopically. Proteins were characterized by their amino acid composition and starch-gel electrophoretic patterns. Comparisons were made with proteins obtained from endosperm meal by extraction with different solvents. The slowest-sedimenting protein zone contained typical albumins and globulins soluble in centrifugation buffer. A 2nd zone contained a high mol. wt. protein soluble only in alkali. The amino acid profile of this glutelin protein differed significantly from glutelin extracted from meal with alkali. The 3rd zone contained particles microscopically identical to free protein bodies. The protein in these bodies was characterized as zein. The 4th and fastest-sedimenting zone was identified as protein bodies surrounded by a protein matrix. The matrix protein, which resembled glutelin protein in its solubility properties, differs significantly from the extracted glutelin in amino acid composition. The electrophoretic patterns of the reduced and alkylated proteins of zones 2 and 4 when in combination, resemble the electrophoretic patterns of reduced and alkylated glutelin obtained by direct extraction of endosperm meal.

Cytological Characteristics of Ten-Year-Old Rye-Grass Endosperm Tissue Cultures

Abstract: A clone of perennial rye-grass (Lolium perenne L.) endosperm tissue culture, isolated in 1955, was studied after 10 years of periodic subculturing. Cytological, morphological, and growth data were obtained, which demonstrated that the tissue had remained approximately triploid (3n = 21). On the basis of chromosome counts in 392 cells, the most frequent numbers were 21 (76 counts) and 22 (77 counts). The range of chromosome numbers was 18-50. Surprisingly, only two cells were 18, four cells were 19, and 10 cells were 20 in chromosome number. Moreover, a karyotype analysis suggests that the tissue is not morphologically triploid in a strict sense, since seven triplets of homologs no longer exist. Dicentric chromosomes and fragmented chromosomes were present. The growth of the tissue, in terms of 25-day increase in wet weight, diminished by about 30% in 10 years; and its ability to synthesize starch was reduced.

Some aspects of the morphology, embryology and biology of terniola zeylanica (gardner) tulasne

Abstract: Summary The plant body in Terniola zeylanica (Gardner) Tulasne, a member of the Podostemaceae, consists of a creeping thallus. The flowers are bisexual, hypogynous and trimerous. The anthers are dithecous and all the microsporangia are arranged on the inner side of the anther and parallel to each other. The anther wall consists of four layers. The tapetum is of the secretory type. Quadripartition of the mother cells is simultaneous and the tetrads are isobilateral or tetrahedral. The microspore nucleus divides by an asymmetric spindle and the pollen grains are shed at the two-celled stage. The ovules are anatropous, tenuinucellar and bitegminal with the micropyle formed solely by the outer integument. Both the integuments differentiate simultaneously. The embryo sac is bisporic, five-nucleate and follows the reduced Allium type. A pseudo-embryo sac is formed during early embryogeny. Both entomophily and anemophily are prevalent. Syngamy takes place normally. Previous reports of double fertilization are not confirmed. A primary endosperm nucleus is not formed and there is no endosperm. The development of the embryo follows the Solanad type and the embryo possesses a large, coeno-cytic, haustorial cell. The development and maturation of the seed coat and pericarp have been studied. The cells of the inner epidermis of the ovary wall become binucleate and at times even multinucleate.

Sequential action of cytokinin and gibberellic acid in wheat aleurone tissue.

Abstract: INCUBATION of de-embryoed wheat or barley grains in the presence of gibberellic acid induces α-amylase activity in the endosperm which is greater than that of tissue incubated in the absence of the hormone1,2. The target tissue of gibberellic acid is the aleurone layer3, and the effects of protein synthesis inhibitors4 have indicated that the induction involves a de novo synthesis of the enzyme. Induction of other hydrolytic enzymes in the aleurone tissue by gibberellic acid has also been described5,6.

Embryogeny and Caryopsis Development of Sorghum bicolor (L.) Moench1

Abstract: The morphological development of the caryopsis and embryo of grain sorghum, Sorghum bicolor (L.) Moench, was followed from pollination through 50 days in a cross between varieties 'Reliance' and 'Norghum.' Fertilization occurred 2 to 4 hours after pollination. The primary endosperm nucleus does not have a measurable rest period. The endosperm remains free nucleate for 48 hours after pollination. Three days after pollination, the embryo sac is filled with cellular endosperm. The nucellus is displaced by endosperm 8 days after pollination. The zygote has a rest period of not less than 6 hours or more than 20-22 hours. The first embryonic leaf is initiated at 9 days, and successive leaves are initiated at 10, 15, and 20 days after pollination. The radicle is initiated between 6 and 7 days and is fully defined by 12 days. Vascularization of the embryo consists o£ procambium strands in the embryo axis and the distal lobe of the scutellum. All meristematic activity had terminated by 25 days.

Metabolism of 14C-Maltose in Avena fatua Seeds During Germination

Abstract: Non-dormant and dormant seeds of Avena fatua metabolize (14)C-maltose in different ways: in non-dormant seeds, (14)C-maltose administered to the endosperm is readily converted to sucrose in the scutellum and translocated to the embryo; in dormant seeds, little sucrose is synthesized from (14)C-maltose, and maltose and glucose tend to accumulate in the endosperm. It is suggested that biosynthesis of sucrose is essential for effective transport of the endosperm reserve to the embryonic axis in germinating seeds.

Inter-specific hybrids of Lilium lankongenseFranchet produced by embryo-culture

Abstract: Lilium lankongense crossed with some related species of Lilium produced seeds without endosperm and with very small embryos which would not germinate in soil. Hybrid plants have been obtained from a number of these crosses by culturing excised embryos on sterile nutrient medium. It is suggested that the technique may prove useful in the production of hybrids from other lily species-combinations which are not normally viable.

Identification and genetic control of starch-degrading enzymes in maize endosperm.

Abstract: Three starch-degrading enzymes from liquid endosperm of maize have been separated by means of horizontal acrylamide gel electrophoresis. The three enzymes are tentatively identified as α-amylase (zone 1), β-amylase (zone 2), and α-glucan phosphorylase (zone 3). Electrophoretic variants of these enzymes were found among ten inbred strains examined. Results of genetic crosses with respect to zone 2 amylase show that it is controlled by a pair of alleles (Amy-2 A and Amy-2 B) acting without dominance. It further appears that Amy-2 and Ct (catalase) are linked with 5% recombination frequency.

Detecting endogenous growth regulators on the sarcotesta, sclerotesta, endosperm, and embryo by paper chromatography on fresh and old seeds of two papaya varieties.

Abstract: Sarcotesta, sclerotesta, endosperm and embryo of fresh and old (0 and 3 years, respectively) seeds of the P.R. 6-65 and P.R. 8-65 papaya varieties were separately analyzed by paper chromatography to determine the presence of natural growth inhibitor that might be responsible for the reduction in germination of papaya seeds during storage. The results showed that in the innermost seed parts (embryo and endosperm) endogenous growth promoters were found while the outermost structures (sarcotesta and sclerotesta) contained inhibitors. Therefore, it is possible that the natural growth inhibitors of this seed might be minimized by removing the sarcotesta (the gelatinous envelope) of the seed, which contains the most endogenous growth inhibitors, plus a careful washing to eliminate the soluble inhibitors of the sclerotesta during the extraction of seeds from the fruits.

Occurrence of RNA in Glyoxysomes From Castor Bean Endosperm

Abstract: The finding that in the endosperm of germinating castor bean, the enzymes of the glyoxylate cycle were housed in a special organelle, the glyoxysome (1,2) raised the question of its biogenesis. We have shown that glyoxysome protein increases strikingly during the early stages of germination and concluded that rapid formation of new organelles occurs at this time (8). When the individual organelle fractions separated by sucrose density gradient centrifugation (2) were examined, RNA was shown to be present in mitochondria, proplastids, and glyoxysomes. In this report results are presented on the nucleic acid content of glyoxysomes subjected to further purification by means of flotation gradients.