Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Germination”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 991 records · Page 55Linked to original sources
PubMed1979

Possible Involvement of the Alternative Respiration System in the Ethylene-stimulated Germination of Cocklebur Seeds.

Respiration of nondormant upper cocklebur (Xanthium pensylvanicum Wallr.) seeds was enhanced by exogenous C(2)H(4), proportionally to the concentration of C(2)H(4) and the duration of presoaking of the seeds. Benzohydroxamic acid (BHM) and salicylhydroxamic acid (SHM), inhibitors of alternative respiration, inhibited both the germination of nondormant lower cocklebur seeds and the respiration of the upper seeds presoaked for periods of 12 to 30 hours. Both the growth and respiration of axial and cotyledonary tissues were also inhibited by BHM. Moreover, BHM inhibited both the C(2)H(4)-induced germination of the upper seeds and their C(2)H(4)-stimulated respiration; the inhibition occurred only with concomitant addition of C(2)H(4) and BHM. The respiration of seeds with a secondary dormancy induced by presoaking for prolonged periods was markedly stimulated by C(2)H(4) but not suppressed by BHM. It was suggested that the alternative respiration system may be involved in the normal germination process of cocklebur seeds, secondary dormancy may result from its inactivation, and C(2)H(4) may exert its germination-promoting action by stimulating the alternative respiration. The effects of BHM and SHM can suggest but not prove the involvement of the alternative respiration in seed germination.

Journal Article↗
PubMed1981

Phytochrome Action during Prechilling Induced Germination of Betula papyrifera Marsh.

Seeds of paper birch (Betula papyrifera Marsh.) were induced to germinate by prechilling at 3 C or by red light. The light requirement was mediated by phytochrome and the action of phytochrome during prechilling was investigated. Red irradiation (R) prior to prechilling markedly enhanced the effectiveness of the prechilling treatment in inducing subsequent germination at 18 C. Reversal of this enhancement by far-red irradiation (FR) was more effective when FR was supplied after a 1-week prechill treatment than after a 2-week treatment. The R enhancement effect exhibited a sharp drop as prechilling temperature was increased from 5 to 7 C. This decline is consistent with a membrane phase transition at about 7 C where Pfr action is diminished by a loss in sensitivity of its receptor sites. Although phytochrome action was observed during prechilling treatments, the seeds failed to germinate at prechilling temperatures. Therefore, it was concluded that while potentiation of germination by Pfr occurred during prechilling, some other reaction(s) leading to radicle protrusion requires higher temperatures. In one seed source loss of germination potential was observed with protracted storage at 3 C. This was prevented by R supplied during the prechilling treatment. Taken collectively the data suggest that action of phytochrome during prechilling is accentuated in these seeds by two factors: (a) an increase in the sensitivity (or number) of Pfr receptor sites; and (b) preservation of Pfr by deferment of thermal reversion.

Journal Article↗
PubMed1981

Phase-sequence of redroot pigweed seed germination responses to ethylene and other stimuli.

Phase-sequence studies showed that light, ethylene, and high temperature each enhanced germination of redroot pigweed (Amaranthus retroflexus L.) seeds when given during the first 24 hours of seed imbibition. Responses were maximal during the first 12 hours. After 48 hours all three stimuli given together caused 75% germination but each alone was ineffective. The main influence of water potential on seed germination occurred at about 24 hours, but the influence of CO(2) extended into the second and third days. Germination was reduced by water stress (-4 bars) or CO(2)-free air, but ethylene reversed the reduction even when administered after several days incubation. This suggested that environmental and hormonal factors affected redroot pigweed seeds at two distinct stages in the sequence of germination events.

Journal Article↗
PubMed1981

Reevaluation of the cyanide resistance of seed germination.

Although high levels of KCN (53 micromoles per gram fresh weight of seed, corresponding to 3.2 millimolar) failed to block germination of lettuce seeds incubated in covered Petri dishes, the same levels totally blocked germination in sealed dishes. Inhibition was reversed by removing the seal. Placement of KCN remote from seeds also blocked germination in closed systems. Cyanide effectiveness was enhanced by acidifying the KCN solution but negated by the presence of a trap containing strong alkali. Low levels of aqueous HCN (2.6 micromoles HCN per gram, corresponding to 0.16 millimolar) injected into sealed dishes gave maximal inhibition of germination, suggesting that the effectiveness of KCN was due to formation of HCN in KCN solutions. Studies with nine additional crop species generally supported the interpretation that cyanide inhibition of germination has been underestimated in the past due to escape of volatile HCN from open systems.

Journal Article↗
PubMed1982

Different Rates of Metabolism of Soybean Proteinase Inhibitors during Germination.

During germination, the content of the major Bowman-Birk proteinase inhibitor (BB-E) in the cotyledons of soybean (Glycine max [L.] Merrill cv. Fiskeby V) seeds decreases, becoming a minor form by the sixth day of germination. One of the three other minor species (BB-D) of this inhibitor in the dry seed increases to become the major form in six-day cotyledons. The other two minor species (BB-C and BB-F) also appear to decrease during germination, but at a slower rate compared to the original major inhibitor form BB-E. By 13 days of germination, no distinct Bowman-Birk inhibitor species can be discerned in the cotyledons. The content of the major Kunitz proteinase inhibitor (K-B) also decreases during germination, but much more slowly. One new form of the Kunitz inhibitor (K-A) becomes apparent by the sixth day. By the 13th day, the proportion of the main isoinhibitor to the late-appearing form is approximately two to one. This difference in the rates of disappearance and appearance of isoinhibitor species in the Bowman-Birk and Kunitz proteinase inhibitor classes suggests a differential metabolism of these two types of proteins and a possible difference in function in the soybean plant.

Journal Article↗
PubMed1983

Enzymic mechanism of starch breakdown in germinating rice seeds : 15. Immunochemical study on multiple forms of amylase.

The formation of multiple forms of amylases in germinating rice (Oryza sativa L. cv Kimmaze) grains was examined by means of isoelectric focusing, cross-immunoelectrophoresis, and rocket-line immunoelectrophoresis followed by a reaction of enzymic characterization by using beta-limit dextrin or starch as substrate. The constituents detected by isoelectric focusing were identified as three electrophoretically heterogeneous antigens. The major alpha-amylase bands A and B corresponded to a same antigen, the main portion of which was produced within 2 days' germination. The bulk of alpha-amylase D appeared between 2 and 4 days' germination. Component E, a debranching enzyme according to its action on the beta-limit dextrin, already exists in the ungerminated seeds; its amount decreases within the first 2 days of germination and increases again thereafter.Evidence showing that beta-amylase (band C) is produced by the scutellum at an early stage of germination was provided. The enzyme appeared in a suspension of the scutellum after a prolonged incubation.

Journal Article↗
PubMed1983

Subunit Structure Differences in RNA Polymerase II Purified from Ungerminated versus Germinated Wheat Embryos.

DNA-dependent RNA polymerase II (RNAP II) was purified from wheat embryos germinated for 0, 12, 24, and 36 hours and examined with several polyacrylamide gel electrophoretic systems. A changing electrophoretic pattern of RNAP II was observed on nondenaturing polyacrylamide gels. Subunit structure analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) indicated that from ungerminated embryos, RNAP IIA was almost exclusively obtained which has a subunit structure identical to that established for wheat germ RNAP II previously (Jendrisak, Burgess 1977 Biochemistry 16: 1959-1964). Twelve polypeptides with molecular weights x 10(-3) of 220, 140, 42, 40, 27, 25, 21, 20, 17.8, 17.0, 16.3, and 16.0 were routinely found to be associated with the purified enzyme. From embryos germinated for 36 hours, RNAP IIB was almost exclusively obtained which has a largest subunit of 180,000 mol wt instead of 220,000. From embryos germinated for 24 hours, an approximately equimolar mixture of RNAP IIA and IIB was obtained. Peptide maps of the 220,000 and 180,000 mol wt polypeptides of RNAP IIA and IIB were virtually identical, indicative of a precursor-product relationship for the two polypeptides. In addition to these results, SDS-PAGE indicated that the stoichiometry of the 27,000 mol wt polypeptide increased at the expense of the 25,000 mol wt polypeptide during germination and concomitantly with the appearance of the 180,000 molecular weight polypeptide. No modifications (e.g. gain, loss, or altered mobilities on analytical gels) in any of the other RNAP II subunits were observed in enzyme purified from embryos after various times of germination as determined by a variety of electrophoretic analyses under denaturing conditions.

Journal Article↗
PubMed1984

Spore Germination and Rhizoid Differentiation in Onoclea sensibilis: A Two-Dimensional Electrophoretic Analysis of the Extant Soluble Proteins.

Following a geometrically asymmetrical cell division during germination of spores of the fern Onoclea sensibilis L., the small cell differentiates into a rhizoid and the large cell divides to form the protonema. Using silver-staining of two-dimensional gels, we have examined the soluble proteins of spores during germination and of separated rhizoid protoplasts and protonemal cells. Of over 500 polypeptides followed, nearly 25% increased or decreased in prominence during spore germination and the initial phases of rhizoid elongation. Soluble proteins from purified protoplasts of young rhizoids were quantitatively different from those of protonemal cells and germinated spores. Nine polypeptides which appeared after cell division were substantially more prominent in rhizoid protoplasts than in whole germinated spores and have been putatively designated rhizoid-specific polypeptides. The differences in the soluble protein composition of young rhizoids and protonemal cells probably reflect the differential organelle distribution between the two cells as well as differential net protein synthesis in the cytoplasms of the two cells.

Journal Article↗
PubMed1984

Secretion of alpha-amylase by the aleurone layer and the scutellum of germinating barley grain.

alpha-Amylase activities in extracts of different parts of barley grain (Hordeum vulgare L. cv Himalaya) were low after 1 day of germination at 20 degrees C, but they began to increase afterwards. In the scutellum and the aleurone layer, the increases were small, but in the starchy endosperm a great increase took place between days 1 and 6.When the aleurone layers were separated from germinating whole grains and incubated in 10 millimolar CaCl(2), the alpha-amylase activity in the medium increased linearly for about 30 to 60 minutes, indicating secretion. The activity inside the aleurone layer decreased only slightly during the incubation, indicating that secretion of alpha-amylase was accompanied by synthesis. The rates of secretion in vitro by the aleurone layers separated at different stages of germination corresponded rather well to the rate of accumulation of alpha-amylase activity in the starchy endosperm in a whole grain.Scutella separated after 1 day of germination released small amounts of alpha-amylase activity into 10 millimolar CaCl(2). This release was linear for at least 1 hour and did not occur at 0 degrees C; it is therefore likely to be due to secretion. At later stages of germination, the secretion by the scutella was slower than at day 1 and the total secretion accounted for only 5 to 10% of the increase of alpha-amylase activity in the starchy endosperm in a whole grain.Since the times from the separation of the parts of the grain to the beginning of the secretion assay (10-40 minutes) as well as the duration of the assay itself (20-60 minutes) were short, the rates of secretion by the separated grain parts are likely to represent those in an intact grain. The results indicate therefore that at least in the conditions used the bulk of the total alpha-amylase in the starchy endosperm is secreted by the aleurone layer, the contribution by the scutellum being only 5 to 10% of the total activity.

Journal Article↗
PubMed1985

Control of Seed Germination by Abscisic Acid : III. Effect on Embryo Growth Potential (Minimum Turgor Pressure) and Growth Coefficient (Cell Wall Extensibility) in Brassica napus L.

The physical mechanism of seed germination and its inhibition by abscisic acid (ABA) in Brassica napus L. was investigated, using volumetric growth (= water uptake) rate (dV/dt), water conductance (L), cell wall extensibility coefficient (m), osmotic pressure ( product operator(i)), water potential (Psi(i)), turgor pressure (P), and minimum turgor for cell expansion (Y) of the intact embryo as experimental parameters. dV/dt, product operator(i), and Psi(i) were measured directly, while m, P, and Y were derived by calculation. Based on the general equation of hydraulic cell growth [dV/dt = Lm/(L + m) (Delta product operator - Y), where Delta product operator = product operator(i) - product operator of the external medium], the terms (Lm/(L + m) and product operator(i) - Y were defined as growth coefficient (k(G)) and growth potential (GP), respectively. Both k(G) and GP were estimated from curves relating dV/dt (steady state) to product operator of osmotic test solutions (polyethylene glycol 6000).During the imbibition phase (0-12 hours after sowing), k(G) remains very small while GP approaches a stable level of about 10 bar. During the subsequent growth phase of the embryo, k(G) increases about 10-fold. ABA, added before the onset of the growth phase, prevents the rise of k(G) and lowers GP. These effects are rapidly abolished when germination is induced by removal of ABA. Neither L (as judged from the kinetics of osmotic water efflux) nor the amount of extractable solutes are affected by these changes. product operator(i) and Psi(i) remain at a high level in the ABA-treated seed but drop upon induction of germination, and this adds up to a large decrease of P, indicating that water uptake of the germinating embryo is controlled by cell wall loosening rather than by changes of product operator(i) or L. ABA inhibits water uptake by preventing cell wall loosening. By calculating Y and m from the growth equation, it is further shown that cell wall loosening during germination comprises both a decrease of Y from about 10 to 0 bar and an at least 10-fold increase of m. ABA-mediated embryo dormancy is caused by a reversible inhibition of both of these changes in cell wall stability.

Journal Article↗
PubMed1985

Analysis of the Effect of Light and Temperature on the Fluence Response Curves for Germination of Rumex obtusifolius.

Both red light (10 minutes) and 35 degrees C treatment (60 minutes) stimulate the germination of seeds of Rumex obtusifolius otherwise maintained in darkness at 25 degrees C. Fluence response curves were determined for the effect of red light to stimulate germination of seeds with and without 35 degrees C treatment. The endogenous far-red absorbing form (Pfr) level in the seeds was determined using short saturating fluences of wavelengths of light which maintain different proportions of phytochrome as Pfr at equilibrium. In the seed batches investigated, the endogenous Pfr level was found to be 4% or less of the total phytochrome. High dark germination after 35 degrees C treatment does not result from an increase in sensitivity of the whole population to Pfr. Calculated fluence response curves for germination which best fit the experimental data suggest that seeds germinate in darkness after 35 degrees C treatment because of a nonphytochrome-related process (overriding factor).

Journal Article↗
PubMed1986

Amino Acids Content in Germinating Seeds and Seedlings from Castanea sativa L.

During germination the chestnut (Castanea sativa L.) var ecotype 33 accumulates a large amount of asparagine in the cotyledons. This compound also accumulates in the growing axis:shoots and roots. In the cotyledons, gamma-aminobutyrate (GABA) represents a major amino compound during germination and early seedling growth. In young seedlings, 35 days old, arginine predominates over the other soluble amino acids, particularly in roots. Five enzymic activities involved in arginine and GABA have been measured in the storage organ of the seed: arginase and ornithine carbamyltransferase decrease during germination indicating the slowing down of the urea cycle. In contrast, ornithine aminotransferase increases. Glutamate decarboxylase is particularly active about 21 days after imbibition and GABA aminotransferase activity decreases during germination. These two activities are in good agreement with the likely transport of GABA from cotyledons to growing axis. Asparagine, arginine, and GABA are the three amino compounds obviously involved in the mobilization of nitrogen reserves in the germinating chestnut seeds Castanea sativa.

Journal Article↗
PubMed1986

Role of Ethylene in Lactuca sativa cv ;Grand Rapids' Seed Germination.

Promotion of thermoinhibited (30 degrees C) lettuce (Lactuca sativa cv ;Grand Rapids') seed germination by ethylene is similar to the action of the gas in other hormonal systems. Ethylene was more active than propylene and ethane was inactive. An inhibitor of ethylene production, aminoethoxy-vinylglycine, reduced ethylene evolution and germination. Inhibitors of ethylene action such as, 5-methyl-7-chloro-4-ethoxycarbonylmethoxy-2,1,3-benzothiadiazole, 2,5-norbornadiene, and silver thiosulfate inhibited germination and the effect was reversed by the addition of ethylene to the gas phase. The action of ethylene appears to be due to the promotion of radial cell expansion in the embryonic hypocotyl. The action of N6-benzyladenine and fusiccocin, which also overcome thermoinhibition, appears to be due to a promotion of hypocotyl elongation. None of the germination promoters studied appeared to function by lowering the mechanical resistance of the endosperm to embryonic growth. Data presented here are consistent with the view that ethylene plays a role in lettuce seed germination under thermoinhibited and normal conditions.

Journal Article↗
PubMed1987

Cottonseed malate synthase : biogenesis in maturing and germinated seeds.

The activity of malate synthase (MS) (EC 4.1.3.2) appears and increases during cotton (Gossypium hirsutum L.) seed maturation, persists through desiccation and imbibition, then increases again following germination. The research reported herein is a comparative study of the synthesis and acquisition of MS into glyoxysomes as they occur in maturing and germinated seeds. Rate-zonal centrifugation of cotyledon extracts revealed that the 5 Svedberg unit (S) cytosolic form of MS was the only form present at 42 days postanthesis (DPA) when activity was first detectable. At later stages (48 DPA, 0 day, 26 hours, and 48 hours), both the 5S and glyoxysomal 20S forms were present, with the 20S form becoming much more prevalent. Western blot analyses revealed that no other form(s) of MS were present in the phosphate-buffered gradients, and that 5S and 20S forms had the same subunit molecular weight in maturing and germinated seeds. Comparisons of radiospecific activity of MS immunoprecipitates following in vivo labeling with [(35)S]methionine for varying time intervals provided strong evidence for a 5S-precursor to 20S-product relationship during both seed maturation and seedling growth. Comparisons of MS labeled in vivo and in vitro in wheat germ and rabbit reticulocyte lysates programmed with poly(A)(+)RNA (from maturing and germinated seeds) revealed no detectable differences in subunit molecular weights. These results reinforced our other data indicating that MS was synthesized in the cytosol and acquired by glyoxysomes in both maturing and germinated cotton seeds without involvement of an intervening aggregate pool in the endoplasmic reticulum, or via processing of a cleavable precursor molecule. MS was translated from poly(A)(+)RNA extracted from 28 DPA cotton seeds. This was nearly 2 weeks before MS activity or protein was detected in vivo. This finding invites further study on the regulation of RNA transcripts during maturation.

Journal Article↗
PubMed1988

Interrelations between Carbon Dioxide and Ethylene on the Stimulation of Cocklebur Seed Germination.

Interrelations between CO(2) and C(2)H(4) on promotion of seed germination were examined in more detail at 23 degrees C with presoaked upper seeds of Xanthium pennsylvanicum Wallr. The germination-promoting effect of C(2)H(4) decreased gradually as its application time was delayed during a soaking period, whereas CO(2) was most promotive in application at 5 days of soaking, then its effect declined. CO(2) and C(2)H(4) were additive in earlier soaking periods and synergistic in later periods. Such changes in germination behavior in response to CO(2) and/or C(2)H(4) during a soaking period were closely associated with growth responsiveness of the axial tissues, but not of the cotyledonary ones. Growth responsiveness of axial tissues to CO(2) or C(2)H(4) disappeared finally during a soaking period, but their extinct responsiveness to any one of these gases was almost fully restored in the simultaneous presence of the other. The extinct responsiveness to CO(2) was partially recovered by a preexposure to C(2)H(4). This suggests that in the later period of soaking, unlike the case in a very early period of soaking, the C(2)H(4)-sensitive phase for seed germination precedes the CO(2)-sensitive phase in which CO(2) potentiated axial growth. The restoration of CO(2) responsiveness in axial growth occurred not only after C(2)H(4) treatment but also after exposure to 8 or 33 degrees C or after KCN treatment. Thus, secondarily dormant Xanthium seeds could germinate in response to CO(2) alone, when they were previously exposed for shortterms not only to C(2)H(4) but also 8 degrees C, 33 degrees C, or KCN.

Journal Article↗
PubMed1989

Distinct lipoxygenase species appear in the hypocotyl/radicle of germinating soybean.

Three lipoxygenase isozymes are synthesized in developing soybean (Glycine max [L.] Merr. cv Williams) embryos and are found in high levels in cotyledons of mature seeds (B Axelrod, TM Cheesbrough, S Zimmer [1981] Methods Enzymol 71: 441-451). Upon germination at least two new protein species appear which are localized mainly (on a protein basis) in the hypocotyl/radicle section. These lipoxygenase species appear also in seedlings of each of three lipoxygenase nulls (1x1, 1x2, and 1x3) deficient in one of the dormant seed lipoxygenases. The germination-associated species are distinguishable from dry seed lipoxygenase by their more acidic isoelectric points as revealed in isoelectric focusing gels. They are active from as early as 2 to at least 5 days after the start of imbibition. These germination-stimulated species qualify as lipoxygenase by their inhibition by the lipoxygenase inhibitors n-propyl gallate and salicyl hydroxamic acid and their lack of inhibition by KCN. Further, they are not active on the peroxidase substrate pair H(2)O(2)/3-amino-9-ethyl carbazole. They are recognized on Western blots by polyclonal antibodies to the seed lipoxygenase-1 isozyme and the major induced species has a molecular weight of approximately 100,000, similar to that of the cotyledon lipoxygenases. These lipoxygenases appear to be synthesized de novo upon germination since they comigrate with radioactive protein species from seeds germinated in [(35)S]methionine.

Journal Article↗
PubMed1990

Control of Germination in Striga asiatica: Chemistry of Spatial Definition.

Striga asiatica (Scrophulariaceae), a member of a heterogeneous group known as the parasitic plants, is totally dependent on host root attachment for survival. In agar, Striga seeds germinated in high percentages within 5 millimeters of a sorghum (Sorghum bicolor (L.) Moench) host root surface, and no germination was observed at distances greater than 1 centimeter. This spatially restricted germination may be explained by the chemistry of a single compound, 2-hydroxy-5-methoxy-3-[8'Z, 11'Z)-8', 11', 14' -pentadecatriene]-p-hydroquinone, structure 1, which is exuded by sorghum roots. The presence of the compound was chemically imaged with pigments such as methylene blue. The use of methylene blue suggested that structure 1 was exuded along the entire surface of the root for long periods. This exudation and the inherent instability of structure 1 together establish an apparent steady state concentration gradient of the germination stimulant around the sorghum root. The Striga seed must be exposed to micromolar concentrations of 1 for >/=5 hours before high germination percentages were observed. Such a requirement for a long term exposure to a steady state concentration of an inherently labile, exuded compound would provide an extra degree of resolution to signal detection and host commitment in Striga parasitism.

Journal Article↗
PubMed1990

Sugar metabolism in germinating soybean seeds: evidence for the sorbitol pathway in soybean axes.

Characterization of sugar content and enzyme activity in germinating soybean (Glycine max L. Merrell) seeds led to the discovery of sorbitol accumulating in the axes during germination. The identity of sorbitol was confirmed by relative retention times on high-performance liquid chromatography and gas liquid chromatography and by mass spectra identical with authentic sorbitol. Accumulation of sorbitol in the axes started on day 1 of germination as sucrose decreased and glucose and fructose increased. Sucrose also decreased in the cotyledons, but there was no accumulation of sorbitol, glucose, or fructose. Accumulation of sorbitol and hexoses was highly correlated with increased invertase activity in the axes, but not with sucrose synthase and sucrose phosphate synthase activities. Sucrose synthase activity was relatively high in the axes, whereas the activity of sucrose phosphate synthase was relatively high in the cotyledons. Ketose reductase and aldose reductase were detected in germinating soybean axes, but not in cotyledons. Fructokinase and glucokinase were present in both axes and cotyledons. The data suggest a sorbitol pathway functioning in germinating soybean axes, which allows for the interconversion of glucose and fructose with sorbitol as an intermediate.

Journal Article↗