bluuebunny/crossref_metadata_2025_split huggingface dataset:
Watermelon seed germination. 2. Osmomanipulation of photosensitivity
Authors: Thanos C. A. , Mitrakos K. 
Published: September 2008

AbstractSeed germination of watermelon (Citrullus lanatuscv. Sugar Baby) was fully suppressed by intermittent far-red (FR) irradiation (1 min every 30 min). When the intervening dark period was increased, a linearly increasing final germination percentage was obtained. However, a 4-day intermittent FR treatment induced phytochrome-controlled dormancy and the longer the dark interval the deeper was the dormancy of the non-germinated seeds. When seeds were soaked in a fully inhibitory osmotic solution, no dormancy was imposed. However, a single FR pulse at the time of transfer induced partial, secondary dormancy; the kinetics of the imposition of dormancy followed a negative exponential curve (half-life 1.5 days; 3 days for the cultivar Crimson Sweet). Seeds osmotreated for 10 days in darkness and subsequently dehydrated (with and without a final FR pulse) acquired germination characteristics similar to those in light-requiring and dark-germinating achenes, respectively, of the lettuce cultivar Grand Rapids. In the light-requiring osmomanipulated seed population, the induction of germination was brought about by the low-energy reaction of phytochrome, chilling, dry storage and decoating. The transformation through osmomanipulation of the dark-germinating watermelon seeds (the inhibition of which required prolonged exposure to light) to positively or negatively photosensitive seeds (that responded to brief light pulses), might be attributed to the slow relaxation of existing meta-Fa and meta-Rb phytochrome intermediates to Pfrupon hydration.
Development of desiccation tolerance in Norway maple (Acer platanoides L.) seeds during maturation drying
Authors: Hong T. D. , Ellis R. H. 
Published: September 2008

AbstractNorway maple (Acer platanoides L.) seeds were harvested at different stages of seed development and maturation in 1989–91. As maturation drying progressed, the seed populations showed increasing desiccation tolerance: at 67–69% moisture content, no seeds survived desiccation below 10% moisture content; maturation drying to 55–57% moisture content (values corresponding with the end of the seed-filling phase) improved desiccation tolerance, but nevertheless most seeds were unable to withstand desiccation to 5–7% moisture content; further maturation drying to 27–28% moisture content enabled the seeds to survive considerable desiccation, no loss in viability occurring in seeds dried to 3% moisture content. This considerable improvement in desiccation tolerance after the end of the seed-filling phase was correlated (P<0.05) with the progress of maturation drying and may be associated with the increase in the potential longevity of seeds of other species that occurs during seed development subsequent to seed filling.
Germination of the seeds of parasitic angiosperms
Authors: Logan D. C. , Stewart G. R. 
Published: September 2008

AbstractTotalling more than 3000 species, parasitic angiosperms are a most diverse group of organisms. Classified as either shoot or root parasites according to site of attachment, plant parasites are further classified, according to the degree of parasitism, into one of two divisions: holoparasitic or hemiparasitic. Within these divisions, angiosperm parasites are either obligate or facultative.Obligate parasites cannot survive to maturity without attaching to a host plant, thus the need to germinate in close proximity to a host first characterizes the specialized germination and seed dispersal strategies of these plants. However, seeds of all species of the rootholoparasitic Orobanchaceae and four genera within the Scrophulariaceae have evolved very specialized germination strategies. Once the seeds have undergone an after-ripening period, they require a prolonged imbibition period at temperatures of approx. 30°C before they acquire the potential to germinate. Minute seeds with very little reserves, they must germinate within millimetres of the host root for successful host attachment and continued survival. To this end, germination only occurs in responseto specific chemical germination triggers released from the host root. InStriga hermonthica(Del.) Benth., the perception of the host-derived trigger results in stimulation of endogenous ethylene production and it is this ethylene that initiates germination. It is proposed that the chemical triggers released from the host be consideredas ‘elicitors’ which function primarily as allelochemicals and that the parasite seeds have become adapted in such a way as to have an absolute requirement for external germination triggers.
Changes in protein synthesis in embryonic axes after long-term storage of maize seeds
Authors: Aguilar R. , Reynoso E. , Albores M. , de Jiménez E. Sánchez 
Published: September 2008

AbstractThe aim of this work was to analyse the capacity for protein synthesis in embryonic axes from long-term-stored maize seeds, including the role of proline. Embryonic axes from seeds stored for 13 years (S) and non-stored seeds (NS) were incubated in nutrient media after application of [14C]proline. Transformation of [14C]proline into other amino acids was analysed by thin-layer chromatography. After 6 h of incubation, no other labelled amino acids were found. Incorporation of14C into total soluble and cell-wall (proline-rich) proteins was assessed during this period. Incorporation of [14C]proline into specific cell-wall proteins was lower in S than in NS axes.Studies using [35S]methionine showed that protein synthesis was slower in axes of S than in NS seeds. Analyses of these proteins by gel electrophoresis and fluorography revealed qualitative differences between the [35S]methionine proteins synthesized by both types of axes. The NS: S ratios for the [35S]proteins were larger than those from the [14C]proline assays. These data may be interpreted as an indication of differential deterioration of transcription or translation in the axes during long-term seed storage.
Effects of (±)-phaseic acid on developing embryos of barley (Hordeum vulgare, L. cv. Bonanza) culturedin vitro
Authors: Hill R. D. , Durnin D. , Nelson L. A. K. , Abrams G. D. , Gusta L. V. , Abrams S. R. 
Published: September 2008

AbstractThe effects of exogenous phaseic acid (PA) on germination and protein accumulation of cultured immature barley embryos were examined. Chemically synthesized PA was racemic, 87% pure and stable over the course of the experiment. Germination was observable in >90% of the untreated embryos after 3 days of incubation, whereas embryos treated with 10μmabscisic acid (ABA) or PA showed no evidence of germination. Buffer extracts from embryos treated with ABA or PA had similar protein profiles when examined by single and two-dimensional electrophoresis. The profiles differed significantly from those of embryos incubated in the absence of the two compounds. Concentrations of α-amylase inhibitor and barley-germ agglutinin (BGA) increased upon treatment of immature embryos with ABA or PA. This was due tode novosynthesis as there was increased incorporation of radioactivity from35S-labelled amino acids into the proteins in treated embryos. Endogenous ABA content in PA-treated embryos was not significantly different from that in untreated embryos. An analogue of ABA, 2′, 3′-dihydroabscisic acid, which cannot be metabolized to phaseic acid, inhibited germination and caused increased synthesis of α-amylase inhibitor and germ agglutinin. ABA and PA may both be active in promoting responses associated with ABA in barley embryos, but the embryos are more sensitive to ABA.
Relation between protein composition and germination capacity of sunflower seeds
Authors: Reuzeau C. , Goffner D. , Cavalié G. 
Published: September 2008

AbstractProtein composition of sunflower seeds (Helianthus annuusL.) was analysed to identify a possible marker for germination capacity and to evaluate seed viability precociously after harvest and after natural ageing during storage. Electrophoresis on 2-D gels was used to compare total soluble andin vivosynthesized proteins in two seed lots showing different germination capacities. Differences were observed to a greater extent inin vivoprotein synthesis profiles than in total soluble proteins. Inhibition of [35S]methionine uptake and incorporation in seeds with low germinability was also observed. The precise relationship between protein composition and prediction of germinability could not be determined. Other aspects such as membrane damage, capacity for protein synthesis and seed lot homogeneity in relation to germination are discussed.
Coat thickness and hard-seededness in some Medicago and Trifolium species
Authors: Russi L. , Cocks P. S. , Roberts E. H. 
Published: September 2008

AbstractThe seeds of three medics (Medicago orbicularis, M. rigidula and M. rotata) and three clovers (Trifolium stellatum, T. campestre and T. tomentosum) were collected from a pasture in north-west Syria on three occasions: immediately after seed set, at the end of the dry season, i.e. 4 months after seed set, and 16 months after seed set. Complete and sectioned seeds were observed with a scanning electron microscope. Morphological changes and differences in thickness of the seed coat were related to the hard-seededness of the samples collected in the seed bank before the onset of the rainy season. The morphology and structure of the seed coat of all six species were typical of papilionoid legumes. The species with the softest seeds (T. stellatum) showed a very thin and discontinuous cuticular layer at seed maturation (0.16 μm), while a thick and continuous cuticle (4.24 μm) was characteristic of the hardest-seeded species (M. orbicularis). The lens region of seed of all species except T. campestre was weakened after a few months in the field. This weakening was also found in seeds which were certainly hard, but the cracks in the lens region were apparently not deep enough to allow imbibition. Even when large areas of the palisade layer were removed from the lens region of seeds of M. rotata, this was not sufficient to permit water uptake. Differences in the seed coat thickness of the six species accounted for differences in seed dormancy only when seed mass was taken into account.
Seed development in relation to desiccation tolerance: A comparison between desiccation-sensitive (recalcitrant) seeds ofAvicennia marinaand desiccation-tolerant types
Authors: Farrant Jill M. , Pammenter N. W. , Berjak Patricia 
Published: September 2008

AbstractDevelopment of the highly desiccation-sensitive (recalcitrant) seeds of primarily one species,Avicennia marina, is reviewed and compared with the ontogeny of desiccation-tolerant (orthodox) seeds.A. marinaseeds undergo no maturation drying and remain metabolically active throughout development, which grades almost imperceptibly into germination. While PGR control of histodifferentiation is essentially similar to that characterizing desiccation-tolerant seeds, the phase of growth and reserve deposition is characterized by exceedingly high cytokinin levels which, it is proposed, promote a sink for assimilate import. While some starch accumulation does occur, the predominant reserves are soluble sugars which are readily available for the immediate onset of seedling establishment upon shedding. ABA levels are negligible in the embryo tissues during seed maturation, but increase in the pericarp, which imposes a constraint upon germination until these outer coverings are sloughed or otherwise removed. The pattern of proteins synthesized remains qualitatively similar throughout seed development inA. marina, and no LEA proteins are produced. This suggests both that seedling establishment is independent of maturation proteins and that the absence of LEAs and desiccation sensitivity might be causally related. The study onA. marinareveals that for this recalcitrant seed-type, germinationper secannot be defined: rather, it is considered as the continuation of development temporarily constrained by the pericarp ABA levels. This leads to a reexamination of the role of rehydration as key eventsensu stricto, in the germination processes in desiccation-tolerant (orthodox) seeds.
Comparisons between the roles of the fruit tissues, osmoticum and abscisic acid in maintaining tomato seed development and storage protein synthesis
Authors: Berry Tannis , Bewley J. Derek 
Published: September 2008

AbstractFive distinct groups of storage proteins are synthesized by embryos during development in the fruit at 35 days after pollination (35 DAP); none of them is synthesized in germinating embryos 48 h after isolation (48 HASI) of the seeds from the fruit. Endo-β-mannanase, a marker of germination and seedling growth, is produced in the isolated seeds, but not in the developing seedin situ35 DAP. When seeds at this stage are removed from the fruit, but remain in intimate contact with the locular and sheath tissue, they continue to synthesize storage proteins for at least 48 HASI. Removal of the sheath from seeds isolated 35 DAP stops storage protein synthesis, and increases endo-β-mannanase activity. Both abscisic acid (ABA) and osmoticum at physiological concentrations maintain the synthesis of storage proteins in seeds isolated 35 DAP for at least 48 HASI, although osmoticum is more effective in preventing their eventual germination. Thus the effects of the sheath and the locular tissue are mimicked by both ABA and osmoticum in relation to the maintenance of storage protein synthesis in seeds 35 DAP and in the suppression of endo-β-mannanase activity for at least 48 HASI.
Nuclear proteins and the onset of cell proliferation in root meristems ofPisum sativum: QP47 a novel acidic protein
Authors: Chiatante Donato , Onelli Elisabetta 
Published: September 2008

AbstractA protein named QP47 has been purified from quiescent nuclei of root meristems ofPisum sativum, and used to prepare a polyclonal antibody. Immunolocalization of this protein with fluorescent probes revealed a nuclear distribution of thread-like structures. However, the relationship between the distribution of QP47 immunofluorescence and the structural organization of the chromatin required further investigation. The decrease in content of this protein in the nuclei of embryo cells seems to be correlated with the transition from quiescence to proliferation. QP47 degradation seems to depend upon an increase in the state of its phosphorylation. This protein is not present in normally proliferating cells, or in cells whose cell proliferation has been arrested by starvation or differentiation. It is hypothesized that QP47 may be required specifically during the quiescent period for specific structural organization of the chromatin.
Function of DNA synthesis and DNA repair in the survival of embryos during early germination and in dormancy
Authors: Elder Rhoderick H. , Osborne Daphne J. 
Published: September 2008

AbstractDNA synthesis following the addition of water to excised embryos of non-dormant rye and to embryos of non-dormant and dormant genetic lines of Avena fatua has been examined. All the samples exhibit an early unscheduled DNA synthesis, have similar responses to DNA polymerase inhibitors and a similar increase in DNA ligase function for the first 24 h of imbibition, irrespective of whether they germinate or remain dormant. A β-polymerase-mediated DNA repair activity is indicated immediately upon imbibition with the stable incorporation of 3H-methyl-thymidine into high molecular weight DNA. Following γ-irradiation of dry or imbibed embryos, inhibitor results suggest the appearance of an additional α- or δ-polymerase activity in the ensuing repair. Abscisic acid permits the early unirradiated repair synthesis, but like aphidicolin, it inhibits replicative DNA synthesis and partly inhibits the post-irradiation incorporation of thymidine. DNA synthesis takes place continuously throughout dormancy of imbibed embryos: precursor incorporation into DNA cannot be chased in the short term and occurs in the absence of an S-phase or endoreduplication of nuclear DNA. It is proposed that dormant imbibed embryos maintain the integrity of the genome by a continuous but slow replacement of DNA steered by a non-amplifying and modified form of replicative DNA synthesis and that abscisic acid may play a determining role in this process.
The role of plant growth regulators in the development and germination of the desiccation-sensitive (recalcitrant) seeds of Avicennia marina
Authors: Farrant Jill M. , Berjak Patricia , Cutting J. G. M. , Pammenter N. W. 
Published: September 2008

AbstractThe contents of the cytokinins zeatin (Z), zeatin riboside (ZR), and isopentenyladenine (IPA), the combined contents of gibberellins1 + 3 (GA), and the contents of indoleacetic acid (IAA) and abscisic acid (ABA) were measured during the development of the desiccation-sensitive seeds of Avicennia marina (Forssk.) Vierh. During the stage of histodifferentiation the amounts of these plant growth regulators (PGRs) were measured on whole fruits. During the phase of seed growth and reserve accumulation measurements were made on the embryonic axis, cotyledons and pericarp separately. Patterns in the amounts of PGRs present during histodifferentiation were similar to those reported for desiccation-tolerant seeds and it suggested that this process is under similar ‘hormonal’ control in A. marina as in orthodox seeds. Very high contents of cytokinins, particularly ZR, were present in both axes and cotyledons during reserve accumulation. This is thought to be related to the nature of the reserves accumulated (soluble sugars), rather than to the phenomenon of desiccation sensitivity. With the exception of ABA, embryonic contents of PGRs were relatively high at seed shedding, consistent with the rapid germination of this highly recalcitrant seed. ABA contents in the embryo were low during reserve accumulation, but concentrations in the pericarp increased throughout this development stage. ABA in the perticap could act to prevent precocious germination. The low concentrations of ABA in the embryo could be related to the desiccation-sensitivity of the seeds of A. marina.
Development and regulation of (1→3,1→4)-β-glucan endohydrolases in germinating wheat (Triticum aestivum)
Authors: Lai Doreen M. L. , Slade Amanda M. , Fincher Geoffrey B. 
Published: September 2008

AbstractThe development of (1→3,1→4)-β-glucan 4-glucanohydrolase (EC 3.2.1.73) has been examined in germinating wheat (Triticum aestivum cv. Millewa) grain, and in isolated aleurone layers and scutella. Activity is first detected in extracts of intact grain 2–3 days after the initiation of germination and thereafter increases until 6 days. In isolated aleurone layers, (1→3,1→4)-β-glucanase activity is secreted for up to 4 days. Treatment of aleurone layers with gibberellic acid (GA3) results in a 2-fold enhancement of secreted enzyme for the first 2 days, but activity decreases after 2 days. (1→3,1→4)-β-Glucanase secretion from GA3-treated aleurone layers clearly precedes the secretion of amylase and (1→4)-β-xylanase. Small but significant levels of cellulase are secreted from aleurone layers after GA3 treatment. Isolated scutella also secrete (1→3,1→4)-β-glucanase but GA3 has little apparent effect on secretion patterns from this tissue. Proteins secreted from excised aleurone layers and scutella, together with those in homogenates of intact, germinated grain, have been examined by Western blot analysis, using monoclonal antibodies against barley (1→3,1→4)-β-glucanases as probes. In each case the wheat (1→3,1→4)-β-glucanase is recognised only by the monoclonal antibody that is specific for barley isoenzyme El.
Storage lipid formation in seeds
Authors: Murphy Denis J. , Rawsthorne Stephen , Hills Matthew J. 
Published: September 2008

AbstractThe mechanisms and regulation of storage lipid formation in seeds are reviewed. Seed storage lipids are ultimately derived from simple carbon compounds, such as sucrose, which are imported into seeds from source tissues, such as leaves or pods. The partitioning of this important carbon towards storage lipid, carbohydrate or protein is regulated by a complex interaction between genetically-determined endogenous factors and external environmental influences. Storage lipids are synthesized from fatty acids, derived from acetyl-CoA, and glycerol 3-phosphate. Fatty acid biosynthesis and probably acetyl-CoA formation, occurs within the plastids to produce oleoyl-CoA. Further elaboration of oleoyl-CoA to produce polyunsaturates, hydroxylates or very long chain acyl-CoAs occurs on the endoplasmic reticulum, as does the esterification of acyl-CoAs to glycerol-3-phosphate to produce the final triacylglycerol storage oil. The temporal and hormonal regulation of storage lipid accumulation in seeds is discussed.
Identification of the sites of K leakage from imbibing seeds and grains
Authors: Beecroft Penny , Lott John N. A. 
Published: September 2008

AbstractSeeds/grains of four species were imbibed for up to 90 minutes half embedded in agar. The agar was then freeze-dried and treated with a chromatographic reagent to detect the sites of potassium leakage from the imbibing seeds/grains. Soybean (Glycine maxcv. Marathon) and pea (Pisum sativumcv. Little Marvel) leaked K across the entire surface of their testas. Aged pea seeds leaked much more extensively than seeds of a fresher lot of the same cultivar. Squash (Cucurbita maximacv. Warted Hubbard) seeds leaked extensively from the flat sides of the seeds and at the hilum, but only slightly at the margins. Maize (Zea mayscv. Golden Beauty) leaked most extensively across the endosperm-only side (i.e. the side opposite the embryo) of the kernel, and kernels leaked more at the tip-cap end than at the broad end. Energy dispersive X-ray analysis determined that K was present in the testas/pericarps before imbibition in all species studied, and that the peak-to-background ratios of K were lower after the seeds/grains had been exposed to water. Neutron activation analysis verified that K was leaked out of the seeds/grains and absorbed into the agar. Seeds from all species studied showed varying amounts of seed-to-seed variation. These variations can be attributed in part to differences in testa/pericarp structure and condition.
Induction of thermodormancy in Avena sativa seeds
Authors: Corbineau F. , Black M. , Côme D. 
Published: September 2008

AbstractFreshly harvested oat (Avena sativa L.) seeds are considered to be dormant because they are unable to germinate at relatively high temperatures (above 20°–25°C). This primary dormancy results partly from the structures surrounding or adjacent to the embryo (pericarp, testa and endosperm) and partly lies in the embryo itself. Incubation of imbibed dormant seeds at 30°C induces a thermodormancy which is expressed as germination in a narrower temperature range. Induction of thermodormancy is apparent after 3–8 hours at 30°C, is optimal after about 1–2 days at this temperature, but diminishes with longer treatment times. Although whole grains become more dormant as a result of such treatment, the embryos themselves become less dormant, therefore the tissues covering or adjacent to the embryos must have become more inhibiting or the embryos have become more sensitive to their inhibitory action. The germination and sensitivity to ABA or oxygen of embryos isolated from such seeds are no longer so dependent on temperature. The effect of high temperature on primary dormancy and induction of thermodormancy is discussed with reference to sensitivity to ABA and temperature.