Showing papers on "Endosperm published in 1968"

Characterization of glyoxysomes from castor bean endosperm.

Abstract: Electron micrographs are presented which establish the identity of the components of the 3 major bands observed after sucrose density centrifugation of the crude particulate fraction from the endosperm of germinating castor bean seedlings. These are: mitochondria (density 1.19 g/cc), proplastids (density 1.23 g/cc) and glyoxysomes (density 1.25 g/cc). Further evidence is provided on the enzymatic composition of the glyoxysomes. Essentially all of the particulate malate synthetase, isocitrate lyase, catalase, and glycolic oxidase is present in these organelles. The distribution of glyoxysomal enzymes on sucrose density gradients is contrasted with that of the strictly mitochondrial enzymes fumarase, NADH oxidase, and succinoxidase. Malate dehydrogenase and citrate synthetase are present in both organelles. The functional role of glyoxysomes and their relationship to cytosomes from other tissues is discussed.

Fine structural development of the megagametophyte of zea mays following fertilization

Abstract: The changes in cytoplasmic fine structure during the interval between pollination and zygotic division in the megagametophyte of Zea mays are reported. The rate of membrane synthesis appears to be low in the mature unfertilized megagametophyte. This megagametophyte is suggested to be in a state of relative metabolic inhibition. The rate of membrane synthesis is high in the zygote and free nuclear endosperm. After fertilization the swelling of the mitochondria in all cytoplasms is interpreted to reflect a presumed increase in metabolic rate relative to growth. In the zygote and endosperm, endoplasmic reticulum (ER) production is associated with the nuclear envelope. In all of the material the ribosomes not associated with the ER are helical polysomes which increase in length after fertilization. On the basis of permanganate staining, the ribonucleoprotein of the endosperm is suggested to be different from that of the other cytoplasms. The specific plastid form of each cell type does not change during the first few hours after fertilization. Dictyosomes are most numerous and active in the antipodals. They are least numerotus in the egg and zygote. The smallest dictyosome vesicles are in the synergids. Dictyosome number and vesicle size increase in the egg and central cell after fertilization. Similarities among the megagametophytes of several angiosperms are enumerated. THE EMBRYO SAC is uniquely the megagametophytic phase in the life cycle of angiosperms. The developmental pathways, final organization of the mature megagametophyte, and the details of fertilization differ greatly among species (Vazart, 1958). Electron-microscopic studies show that this variation in structure extends also to the sub-cellular level even among identical cell types (van der Pluijm, 1964; Jensen, 1965a, b; Diboll and Larson, 1966; Vazart, 1966; Rodkiewicz and Mlikulska, 1967). Among these studies the work on Gossypium hirsutum by Jensen (1964, 1967) is unique for its inclusion of the initial stages of embryogeny and for its comparative application of methods of electron microscopy, physiology and histochemistry. As part of a continuing study of the female reproductive system of Zea mays, the present paper describes the changes in the cytoplasmic fine structure during the interval between pollination and zygotic division (ca. 30 hr). Zea mays was selected because of the large amount of information already available on the species and for the ease with which the material can be handled. A comparison of the data introduced in this paper with those from the above studies should contribute to a better understanding of the angiosperm megagametophyte, structural 1 Received for publication 4 January 1968. Supported by U.S. Public Health Grant No. 1 ROI GM 13517. The author expresses his appreciation to Miss Dagmara Davis for technical assistance. 2 Present address: Department of Biology, Macon Junior College, Macon, Ga. changes relative to fertilization in angiosperms, and to the total knowledge of the corn plant. MATERIALS AND METHODS-Individual plants of commercially available 'Golden Bantam' corn were grown during the summer in 2-gal plastic containers in the greenhouse. The planting mix consisted of soil, peat and vermiculite. The plants were watered daily with a weak Hoagland's solution supplemented weekly with Bandini Gro-Rite commercial fertilizer. Day length was extended to 2:30 AM with 300-w incandescent bulbs producing 25 ft-c of light at bench level. This latter procedure was adopted to satisfy the requirements of continuing other species in a vegetative state. Temperature was maintained above 70 F at all times. Corn ears were bagged before emergence of silk. Unpollinated ears were collected 1 to 2 days after silk emergence. Fertilized material was collected 22, 24, 28, and 32 hr after hand pollination. Approximately 1-mm-thick sagittal sections of ovules containing the megagametophytes were cut from the ear and placed immediately in cold 3% or 6% glutaraldehyde buffered to pH 7.0 with 0.1 M sodium cacodylate. Megagametophytes surrounded by nucellar tissue (megasporangium) were excised from these sections while immersed in the fixative. Following 6 hr of fixation, the tissue blocks were washed in distilled water or buffer; post-fixed in either 5% unbuffered KMnO4 for 12 hr or in buffered 1 % OS04 for 12 hr; washed again, and then stained for 24 hr with 5 % aqueous uranyl acetate. The

Enzymic Mechanism of Starch Breakdown in Germinating Rice Seeds I. An Analytical Study

Abstract: Time-sequence analyses of carbohydrate breakdown in germinating rice seeds shows that a rapid breakdown of starch reserve in endosperm starts after about 4 days of germination. Although the major soluble carbohydrate in the dry seed is sucrose, a marked increase in the production of glucose and maltooligosaccharides accompanies the breakdown of starch. Maltotriose was found to constitute the greatest portion of the oligosaccharides throughout the germination stage. α-Amylase activities were found to parallel the pattern of starch breakdown. Assays for phosphorylase activity showed that this enzyme may account for much smaller amounts of starch breakdown per grain, as compared to the amounts hydrolyzed by α-amylase. There was a transient decline in the content of sucrose in the initial 4 days of seed germination, followed by the gradual increase in later germination stages. During the entire germination stage, sucrose synthetase activity was not detected in the endosperm, although appreciable enzyme activity was present in the growing shoot tissues as well as in the frozen rice seeds harvested at the mid-milky stage. We propose the predominant formation of glucose from starch reserves in the endosperm by the action of α-amylase and accompanying hydrolytic enzyme(s) and that this sugar is eventually mobilized to the growing tissues, shoots or roots.

Phosphorylases I and II of Maize Endosperm

Abstract: Two phosphorylases have been found in the endosperm of Zea mays. Phosphorylase I is found through all stages of endosperm development and seed germination investigated. The other enzyme, phosphorylase II appears only at the stage of rapid starch biosynthesis and is not found during germination. At 22 days after pollination, the activity of phosphorylase II is 10 times that of phosphorylase I. These 2 phosphorylases are separable by column chromatography and behave differently in several respects.Phosphorylase I cannot utilize maltose as a primer while phosphorylase II does so readily. Furthermore, phosphorylase II can synthesize an amylose-like polymer from a "primer free" system after a lag phase.Phosphorylase II is inhibited severely at pH 5.8 by ATP, GTP, ADP, and GDP, and less drastically by UTP, CTP, UDP and CDP. Phosphorylase I is somewhat inhibited by purine nucleotides but not by pyrimidine nucleotides. In all cases, the inhibition is pH-dependent. Phosphorylase I is inhibited competitively by ATP while phosphorylase II is inhibited non-competitively.Phosphorylase II is markedly stimulated by 10 mm Mg(2+) and by 2 mm ethylenediamine tetraacetic acid while phosphorylase I is relatively little affected.

Carbohydrate Synthesis in Maize

Abstract: Publisher Summary This chapter covers some of the gene mutations associated with carbohydrate changes in maize endosperm and presents some of the current evidence on the nature of carbohydrate metabolism, especially starch synthesis, in maize endosperm The genetic control of polysaccharide and starch synthesis in maize endosperm is amply evident from the discussions presented in the chapter The advantages of using mutant organisms for the clarification of metabolic pathways have been demonstrated repeatedly since the early pioneering work of Beadle and Tatum The large collection and quantities of singular and multiple mutant maize plants and endosperm cultures currently available and the interest of many researchers offer excellent prospects for significant and relatively large contributions to the detailed knowledge of the genetic control and biochemistry of starch and carbohydrate synthesis and the differentiation of maize endosperm within the very near future The interactions of multiple mutations on pathways of starch synthesis offer a promising refinement for analyzing the actual pathways involved Physical studies of the starch granules of the various strains underway provide an additional tool for evaluating the influence of particular mutations on the synthesis and deposition of starch These studies have led the research on carbohydrates in maize endosperm into the areas of enzyme characterization, localization of activity, and aspects of enzyme synthesis of polysaccharides in plants, including enzyme repression and activation

The sterol esters of maize seedlings.

Abstract: 1. The composition of the sterol ester fraction of the shoot, root, scutellum and endosperm of 10-day-old maize seedlings was investigated. 2. The scutellum and endosperm together contain 80% of the sterol ester of the seedling. 3. β-Sitosteryl linoleate is the major sterol ester of the scutellum and endosperm. 4. β-Sitosteryl and stigmasteryl palmitate, palmitoleate, oleate and linoleate are the major sterol esters of the root. 5. In the shoot phytosterol linoleate is less abundant than phytosterol myristate, palmitate, palmitoleate and oleate. 6. There is a greater proportion of cholesteryl ester in the shoot than in the other tissues of the seedling.

Carbon-14 Distribution in Carbohydrates of Immature Zea mays. Kernels Following 14CO2 Treatment of Intact Plants

Abstract: Shortly after Zea mays L. plants were exposed to (14)CO(2), most of the radioactivity in the kernel occurred in the free monosaccharides, glucose and fructose. Later the proportion of (14)C in sucrose increased and that in the monosaccharides declined. These data have been interpreted as showing that the translocated sugar is hydrolyzed prior to or during its movement into the storage cells of the endosperm. This hydrolysis appears to occur in the "pedicel region" of the kernel. After entry into the endosperm tissue, sucrose was rapidly resynthesized from the monosaccharides prior to its utilization in starch synthesis.

Integration and Replication of DNA of M. Iysodeikticus in DNA of Germinating Barley

Abstract: WE have shown1–8 that in germinating barley seeds (1 day old), sectioned perpendicularly to the axis and placed on a drop of bacterial DNA labelled with tritium or carbon-14, the foreign macromolecules are absorbed by the endosperm and migrate to the root, where they are immediately taken up into the cell nuclei, apparently without noticeable degradation or immediate re-utilization in endogenous synthesis. Experiments in CsCl gradients have shown that most of the radioactive molecules found in the DNA of the root cells, up to 2 h after application of the foreign labelled DNA, have the buoyant density of this labelled DNA8,9. Other experiments have followed the fate of these molecules for long times7,9.

Native Growth Inhibitors from Citrus Shoots. Partition, Bioassay, and Characterization

Abstract: A partition method has been devised to separate auxins, gibberellins, and their respective inhibitors in plant extracts. Inhibitors counteracting gibberellin activity have been detected by a modified barley endosperm bioassay. An inhibitor found in young citrus shoots counteracts both auxin and gibberellin activities and behaves during partition and ohromatography like abscisin II.

The composition of soluble nucleotides in the developing wheat grain.

Abstract: A method is described for the extraction and measurement of soluble nucleotides from wheat grain. Nucleotides were separated (80-90% recovery) by paper chromatography followed by electrophoresis. The nucleotides extracted were ADP-glucose, ATP, ADP, AMP, and NAD; UDP-glucose, UTP, UDP, and UMP with smaller quantities of cytidine nucleotides.In grain sampled at 20 days after anthesis, 70% of the UDP-glucose was present in the endosperm and the remainder in the testa and pericarp; 90% of the ADP-glucose was found in the endosperm. Of the four uridine nucleotides UDP-glucose was the most plentiful and the level rose from about 330 mmumoles per g fresh weight on the third day after flowering to 430 mmumoles/g on day 12 and then fell steadily to about 140 mmumoles/g just before complete ripening. Levels of 250 mmumoles and 200 mmumoles per g fresh weight were recorded for UTP and UDP on day 12. Thereafter the content of UTP fell relatively more rapidly than either UDP or UDP-glucose.ATP was the most abundant adenine nucleotide and from 7 days after anthesis to day 40 the quantity per g fresh weight fell from about 350 mmumoles to 100 mmumoles. The level of ADP-glucose rose to a maximum of 140 mmumoles/g between days 15 and 21 and then fell slightly towards maturity while ADP varied between 50 and 80 mmumoles/g. On day 20, coinciding with the maximum rate of starch synthesis in the endosperm, the concentration of ADP-glucose in this tissue was about 0.3 mm, and that of UDP-glucose 0.7 mm.The relationship of these results to the mechanism of transfer of hexose units from sucrose to starch is discussed.

The light promoted germination of the seeds of chenopodium album l.; ii. effects of (rs) – abscisic acid

Abstract: SUMMARY The visible germination phenomena of Chenopodium album seeds can be divided into two stages. The first stage, being light-dependent in these seeds, consists of the splitting of the outer testa layer only and the extending of the radicle from within the seed. This stage is not prevented by incubation in (RS)-abscisic acid (ABA). Only the protrusion of the radicle through the inner testa layer and the underlying endosperm layer (the second stage) is prevented by ABA. This effect is more pronounced in darkness than in light. After 2 weeks of incubation the inhibition can be released by transfer to water. After 4 weeks in most of the seeds only scarification of the inner layers enables the start of rootlet growth. It is assumed that ABA inhibits one or some components of the cell expansion of the embryo.

Studies on the Development of Endosperm in Rice : 11. Development of starch granules in endosperm tissue.

Abstract: Increase in size of the starch granules began to precede from the central portion of endosperm tissue and reached the maximum size (39μ in major diameter) by the 15th day after anthesis falling on around 10 days after begining date of the granule formation. According as a portion of the endosperm tissue was on the more outside, the begining date of the granule formation was delayed more, and the increase in size of the starch granules proceeded at a slower pace. Accordingly, starch granules found in the exterior cell layers were always smaller in size than those found in the interior ones. And the starch granules in the outermost cell layer facing the aleuron layer were delayed most. Their final size was as small as 6μ in major diameter on about the 35th day after anthesis, i.e., on around 25 days after begining of starch granule formation. Average size of the whole starch granules showed increase at the most remarkably rapid pace during the period from 10th to 18th day after anthesis, and continued to show an increase until the 35th day to the extent of 23×19μ, thus completing the increase in size. It was generally found that there was little or no significant difference in size of the starch granules contained in each cell. And that it seemed that there was no any appreciably great difference in the number of starch granules in each cell, irrespective of remarkably great differences in size of cells. Size of starch granules of the sample variety "Yoneshiro" (japonica) was generally larger than that of starch granules of such sample varieties as "T136" and "Mushakudanti" (indica). We inferred the following types of routes of translocation of the material substances composing of starch granules into the endosperm tissue. At the very early stage, direct translocation of substances into endosperm from surrounding nucellus (route a) might be fairly noticeable, besides the supply of substances from the vascular bundle on the outside of dorsal side (conducting strand). In and after milk-ripe stage, route (a) had no longer been noticed. Instead, the route (b) translocation "conducting strand→nucellar epidermis→surface cell layer of endosperm (aleuron layer)→starch cell layers" seemed to have probably played the important role in translocation. In and after dough-ripe stage, it seemed that translocation route has come to be increasingly confined to the route (c) translocation "conducting strand→nucellar projection→dorsal side of endosperm". In spite of the fact that the pathway of starch materials in the endorperm cell was becoming increasingly narrower due to the growing size in starch granules after dough-ripe stage, a considerably large amount of materials have been translocated through the endosperm tissue. From this fact, it is suggested that the starch materials have been translocated not only by the simple physical stream in the cell, but also with a help from a certain "carrier" which pocesses enzymatic or chemical activities.

Germination of light-inhibited seed of nemophila insignis'

Abstract: A B S T R A C T Germination of Nemophila insignis seed is inhibited by light over a wide range of temperatures. At low temperatures the light intensity required for inhibition is higher. At 25 C there is little germination (in darkness as well as in light); at 27.5 C germination is inhibited altogether. Virtually complete germination in light is obtained when the endosperm directly covering the radicle is removed. This operation also improves germination in darkness at 25 C. Mechanical scarification performed elsewhere in the seed is without effect. As with Phacelia tanacetifolia, Nemophila seed apparently fails to germinate in light because the endosperm restrains the expansive growth of the embryo. The embryo of dark-imbibed seed develops a force which enables it to overcome the physical resistance of the endosperm. Light inhibits the process which leads to generation of "expansive force." Gibberellic acid at 5 X 10-4 M stimulates germination in light and in the dark. Abscisic acid at 10-4 M inhibits germination; at 10-6 M it inhibits only root growth. The inhibition of germination or root growth caused by abscisic acid cannot be reversed by gibberellic acid. Eighty per cent oxygen under certain conditions promotes germination. The rate of 02 uptake is enhanced in oxygen-enriched atmosphere; however, there is no corresponding increase in the rate of CO2 output. Thus high oxygen tension enhances an oxidative process other than respiration. This reaction is favorable to seed germination.

Endogenous Gibberellins of a Radiation Induced Single Gene Dwarf Mutant of Bean

Abstract: The distribution of endogenous gibberellins in Dwarf-1, a single gene dwarf mutant of Mexico 80-R red beans, was studied. Parallel extraction and fractionation of seeds of this mutant and those of a normal homozygous line followed by thin layer chromatography and bioassays using Rumex obtusifolius, wheat seed endosperm and dwarf bean plants revealed that a stem elongation control factor was contained in the non-acidic fraction from normal, but not from Dwarf-1, seeds. It was concluded that the single gene mutation causes a block either in gibberellin precursor formation or in production of a non-acidic fraction gibberellin-like substance.

Time of initiation of the barley endosperm response to gibberellin A3, gibberellin A14 and kaurene

Abstract: Gibberellin A14 and kaurene, precursors of gibberellin A3, are active in the barley endosperm reducing-sugar assay, but require longer incubation periods for activity to be observed than does GA3. This finding shows that the incubation period must be considered when determining whether a compound is active in this assay. The longer incubation periods required by GA14 and kaurene may reflect reduced rates of penetration, or reduced activity within the cell, or the time required for conversion to a physiologically active form.

The Presence of an Abscisic Acid like Factor in Nonviable Rice Seeds

Abstract: Experiments were carried out with viable and nonviable rice seeds to detect the nature of germination inhibitors. An abscisic acid like factor is present in nonviable seeds but absent in viable ones. The main source of the factor is the embryo although measurable amounts are also obtained from the husk; it is not found in the endosperm however. Interaction with GA3 and IAA suggests that both the rice seed inhibitor and abscisic acid are antagonistic to GA3 and partially reversed the IAA induced growth. The similarity of the UV absorption spectra of the inhibitor and abscisic acid also proves its presence in nonviable seeds. The inhibitor suppresses the α-anivlase activity both in intact and excised seeds in the same way as abscisic acid but the suppression is partially overcome with higher concentrations of GA3.

The growth of the young coconut palm (Cocos nucifera L.). I. The role of the seed and of photosynthesis in seedling growth up to 17 months of age

Abstract: The growth of coconut seedlings and the changes occurring within the seed were studied over a period of 17 months from the germination of the coconuts. Removal of the husk prior to germination made possible an estimate of the endosperm content of each seed and also permitted the exact date of germination to be observed. Seedlings were grown with a non-limiting supply of water and nutrients; 63 seedlings were harvested on each of 10 occasions to enable a growth analysis to be made. A high initial relative growth rate, arising through contributions by the endosperm, fell at 4 months to a level which remained roughly constant to 17 months. By 4 months the haustorium had reached its full size, but thereafter the relative contribution from the endosperm via the haustorium was much diminished. Between 4 and 15 months a gradual change over to full dependence on photosynthesis took place. By 17 months less than 10% of the endosperm remained in the nut. The rate of leaf production was constant with time, but the leaf area increased almost exponentially. There was some indication of a positive relationship between net assimilation rate and solar radiation. Some conclusions are drawn concerning cultural methods with young coconuts.

Genetics of Synthesis of β-Sitosterol Esters in Wheat and Related Species

Abstract: THE specificity of synthesis of β-sitosterol esters in the endosperm of the allohexaploid wheat, Triticum aestivum (genomes ABD), is different from that of the allotetraploid wheat, T. durum (genomes AB). Palmitate (P) followed by linoleate (L) are the main esters in the hexaploid, while linoleate accounts for more than 90 per cent of the sito-sterol esters in the tetraploid. Although the phenotypic difference between the two species is the presence of palmitate in T. aestivum, a complete system for palmitate and linoleate (P–L) synthesis is added with the D genome to T. durum (AB), because both Aegilops squarrosa (D) and a synthetic T. spelta (ABD) show the P–L pattern (Fig. 1).

Studies on the Development of Endosperm in Rice : 10. Electron microscopic studies on the development of starch granules in the endosperm cells.

Abstract: Starch deposition in endosperm cell starts from the 4th day after anthesis. At the outset, several numbers of very small starch granula ('granulum' used herein, id defined to be an unit of a compound granule, and 'granule' is defined to be the whole starch content consisting of an amyloplast) deposit almost simultaneously in each proplastid. Cytoplasm of the endosperm cell is in the very rudimental state at this stage, and the proplastids are full of variations in shape, and most of them are irregular oval-shaped ones, but some have amoeba-like shape. The proplastids multiply by means of their own constriction or segmentation division during the subsequent one or two days. Therefore, it can be said that almost all the proplastids are already endowed with several (or at least one) starch granula in the structure from the outset of their formation. With the growth of proplastid in size, number and size of granula become increased also. It is considered appropriate that the developing proplastid should be known as 'amyloplast' after the time when the self-multiplication has ceased and the granula deposition in the plastid stroma has been closed. After this stage, amyloplast takes the oval shape. Starch granulum takes the polyhedral shape in the stroma from the outset of its formation, and it may not be right to say that the space limitation results in change in the granulum shape from spherical to polyhedral one. Although 'shell structure' or 'daily growth rings' is not found in rice starch granulum, the ununiformity in. the stratified structure of the granulum section suggests that there is a fair possibility that the growth of the granulum is accelerated in the manner in which new starch molecules are added to the outside of 'the existing granulum. Amyloplast is enveloped loosely in the plastid membrane of double structure. The membrane has many creases and seems to keep some partial contacts with endoplasmic reticulum. It is also noteworthy that a golgi body (dictiozome) can be found almost always at the near side of amyloplast. Such structure is considered to have some relationship to the introduction of reserve substances into amyloplast and the synthesis of starch in the amyloplast. By the 15th day after anthesis, the starch granules that started to develop from the 4th day reach about 20μ each in major axis, thus almost completing morphologically. In the mature amyloplast, about 50 to 80 granula are included. From the above evidence, it is clear that rice starch granule has the characteristic of compound granule from the start of its development, and undoubtedly it consists of a single amyloplast. Such results support the BUTTROSE'S opinion, but offer opposition to the views on the part of AIMI and MURAKAMI who insisted upon that compound starch granule consisted of several amyloplasts.

Studies on palms: Embryology ofPhoenix sylvestris Roxb.

Abstract: The paper gives an account of the embryology of the genusPhoenix Linn. being intensively studied in this Department.Phoenix sylvestris Roxb. has been investigated as a type. Male and female flowers, pollen grains, development of ovule, male and female gametophytes, endosperm and embryo development were worked out.