bluuebunny/crossref_metadata_2025_split huggingface dataset:
Watermelon seed germination. 1. Effects of light, temperature and osmotica
Authors: Thanos C. A. , Mitrakos K. 
Published: September 2008

AbstractSeeds of watermelon (Citrullus lanatuscv. Sugar Baby) germinated optimally in the dark, throughout the range 20–40°C. Germination was inhibited by continuous (c) irradiation with farred (FR), blue or white incandescent light; short pulses were ineffective. Intermittent FR could fully substitute for cFR; the effect of alternating red and FR pulses during 30-min dark cycles depended upon the timing of the illuminations within each cycle. It is concluded that germination in watermelon is controlled by the low-energy reaction of phytochrome. However, continuous and intermittent red light resulted in partial reductions in germinability. Opening the seed coat at the radicle end enhanced germination in the dark and reduced photosensitivity towards FR. The outer, lignified part of the testa exerted a mechanically restrictive force upon the expanding radicle; this force was estimated to be equivalent to 0.3 MPa. The kinetics, at 25°C in the dark, of the time course of germination and the escape from the inhibitory actions of cFR and osmoticum (0.5mmannitol) were all sigmoid curves, which, upon transformation to normal distributions, had different means, but statistically similar variances. The cFR-irreversible activation of germination by phytochrome and the mannitol-irreversible onset of radicle elongation preceded radicle protrusion (mean at 32 h, 25°C) by 8 and 6 h, respectively. From the results and data on imbition, it is concluded that activation of germination in watermelon takes place during the second, stationary phase of imbibition (20–30 h after sowing at 25°C).
Effects of partial drying on seed germination in the aquatic grasses Zizania palustris L. and Porteresia coarctata (Roxb.) Tateoka
Authors: Aldridge C. D. , Probert R. J. 
Published: September 2008

AbstractPartial drying of non-dormant seeds had little effect on germination behaviour compared with undried controls. In contrast, partial drying resulted in a marked increase in the germination response of freshly harvested (dormant) seeds of Z. palustris. Partial drying also resulted in a 100-fold reduction in the concentration of gibberellins (GA4+7) required for maximum germination. Although the concentration range of applied abscisic acid (ABA) that permitted germination was unaltered, partial drying increased the final germination percentage at all concentrations tested. The concentration of ABA above which germination was reduced in freshly harvested (dormant) seeds of Z. palustris was 3.16 × 10−7m compared with 10−4m in fresh (non-dormant) seeds of P. coarctata. Changes in the germination response of Z. palustris seeds to applied growth regulators, following partial drying or cold stratification might be explained by similar changes in hormonal status.
Physiological aspects of recalcitrance in embryonic axes of Quercus robur L.
Authors: Poulsen K. M. , Eriksen E. N. 
Published: September 2008

AbstractThe sorption isotherm for excised embryonic axes of recalcitrant (i.e. desiccation-sensitive) Quercus robur L. acorns was determined to find the relation between moisture content and water potential. Subsequently, physiological studies on the effect of desiccating the axes to a range of water potentials were undertaken. The respiratory capacity declined steeply after short exposure to water potentials from −5 to −30 MPa. The leachate conductivity increased significantly after exposure to −5 MPa and rose steeply after exposure to between −12 and −40 MPa. Axes were equilibrated at different relative humidities and the proline content showed a 15-fold increase with a peak value at −10 MPa. It was concluded that the critical water potential for initiation of damage was −5 MPa, and that axes accumulated proline as a response to desiccation stress. The embryonic axes from Q. robur behave more like typical vegetative tissue of angiosperms than like orthodox seeds.
Hard-seededness and seed bank dynamics of six pasture legumes
Authors: Russi L. , Cocks P. S. , Roberts E. H. 
Published: September 2008

AbstractSix pasture legumes, common in Syrian grasslands, were investigated. Medicago orbicularis and M. rotata had the largest number of hard seeds, with >90% still hard 5 months after shedding; Trifolium stellatum had the least with <30% of hard seeds; T. campestre, M. rigidula and T. tomentosum were intermediate. Hard-seededness in M. orbicularis and M. rotata varied between years. Scarification of hard seeds resulted in almost complete germination in all species. Alternating temperatures (10/20°C) reduced the rate of germination of scarified T. campestre seeds, but had no effect on germination of scarified or unscarified seeds of T. stellatum. The breakdown of hard-seededness in the field in Syria did not begin until 3 months after shedding and greatly increased when seeds overwintered. Breakdown of hard-seededness was slower when seeds were buried at 5 and 10 cm than when seeds remained on the soil surface. Seedling emergence after the rains started in November was highly correlated with the number of soft seeds observed in October. Similarly, a high correlation was found between the percentage of hard seeds in October and carry-over in the seed bank. In small-seeded species (Trifolium spp.), 39% of the initial seed bank was lost in 2 years by causes other than emergence as seedlings. Such losses were only 7% in larger-seeded species (Medicago spp.). The implications of hard-seededness on the utilization and survival of legumes in grasslands are discussed.
Cytoplasmic glass formation in maize embryos
Authors: Bruni F. , Leopold A. C. 
Published: September 2008

AbstractIn order to examine the occurrence of a glassy state in the cytoplasm of maize embryos as a function of water content, isolated embryos were examined using spin-probe electron spin resonance. The glass transition temperature was determined at various degrees of hydration (h) in the range 0.05–0.25 g H2O g−1 dry sample weight. The obtained phase diagram indicates that, at standard storage temperature (−5°C), the cytoplasm of embryos drier than 0.15 g H2O g−1 is in a glassy state.
Metabolism of polyadenylic acid RNA during seed maturation, ageing and germination in carrot (Daucus carota L.)
Authors: Thompson S. , Bryant J. A. , Brocklehurst P. A. 
Published: September 2008

AbstractPolyadenylic acid (poly(A)) content of carrot seeds reached a peak at 40 days after anthesis and then declined as desiccation occurred. A further decline occurred in the early stages of germination and was more extensive in seeds harvested whilst still immature. Accelerated ageing of seed led to significant losses of poly(A) and the content declined still further when aged seeds were set to germinate. In seeds harvested whilst immature and then subjected to ageing, the resumption of net accumulation of poly(A), a feature of normal germination, was barely detectable or did not occur.
Seed development, the accumulation of abscisic acid and desiccation tolerance in the aquatic grasses Porteresia coarctata (Roxb.) Tateoka and Oryza sativa L.
Authors: Aldridge C. D. , Probert R. J. 
Published: September 2008

AbstractSeeds of Oryza sativa L. (desiccation tolerant, orthodox) completed each of five distinct stages of development approximately 7 days earlier than seeds of Porteresia coarctata (Roxb.) Tateoka (desiccation intolerant, recalcitrant), despite the fact that O. sativa plants matured under cooler conditions. Isolated embryos of O. sativa were more sensitive to rapid desiccation at 6 days post anthesis (DPA) compared with naked caryopses. More than 90% of the latter were desiccation tolerant at 8 DPA and at all stages tested the germination capacity and/or rate of germination was greater following drying. In contrast, drying resulted in a complete loss of viability in seeds of P. coarctata at all stages tested. In both species, abscisic acid (ABA) began to accumulate in embryos mid-way through development. At the respective peaks, the concentration of ABA in P. coarctata was twice that recorded in O. sativa confirming that ABA levels per se do not determine desiccation tolerance in seeds. The possibility that desiccation tolerance is linked to sensitivity to ABA is discussed.
Effects of developmental status and dehydration rate on characteristics of water and desiccation-sensitivity in recalcitrant seeds of Camellia sinensis
Authors: Berjak Patricia , Vertucci Christina W. , Pammenter N. W. 
Published: September 2008

AbstractThe effect of rate of dehydration was assessed for embryonic axes from mature seeds of Camellia sinensis and the desiccation sensitivity of axes of different developmental stages was estimated using electrolyte leakage. Rapidly (flash) dried excised axes suffered desiccation damage at lower water contents (0.4 g H2O (g DW)−1) than axes dried more slowly in the whole seed (0.9 g H2O (g DW)−1). It is possible that flash drying of isolated axes imposes a stasis on deteriorative reactions that does not occur during slower dehydration. Differential scanning calorimetry (DSC) of the axes indicated that the enthalpy of the melting and the amount of non-freezable water were similar, irrespective of the drying rate.Very immature axes that had completed morphogenesis and histodifferentiation only were more sensitive to desiccation (damage at 0.7 g H2O (g DW)−1) than mature axes or axes that were in the growth and reserve accumulation phase (damage at 0.4 g H2O (g DW)−1). As axes developed from maturity to germination, their threshold desiccation sensitivity increased to a higher level (1.3−1.4 g H2O (g DW)−1). For the very immature axes, enthalpy of the melting of tissue water was much lower, and the level of non-freezable water considerably higher, than for any other developmental stage studied.There were no marked correlations between desiccation sensitivity and thermal properties of water. Desiccation sensitivity appears to be related more to the degree of metabolic activity evidenced by ultrastructural characteristics than to the physical properties of water.
Seed protein content and composition of near-isogenic and induced mutant pea lines
Authors: Perez M. D. , Chambers S. J. , Bacon J. R. , Lambert N. , Hedley C. L. , Wang T. L. 
Published: September 2008

AbstractTotal protein content and amounts of albumin, legumin and vicilin have been determined for pea seeds from lines near-isogenic except for genes at therugosusloci,randrb(RR/RbRb; rr/RbRb; RR/rbrb; rr/rbrb). Seeds with the wildtype, round-seeded phenotype (RR/RbRb) had less protein on a total seed dry-weight basis than any of the wrinkled-seeded lines and this protein had a lower proportion of albumin. The lines which had recessive alleles at bothrandrbloci had the highest proportion of protein and the highest proportion of albumin. The roundseeded peas possessed nearly two-fold more legumin than the double recessive line, with proportions for the two single recessive lines falling in between these extremes. Vicilin levels were similarfor all four near-isogenic lines. SDS-PAGE analysis of the isolated albumin, legumin and vicilin fractions revealed no significant differences between the four lines. Differential scanning calorimetry of protein extracts showed that all the wrinkled-seeded near-isolines possessed legumin fractions with diminished thermal stability relative to that from the roundseeded, wild-type line.Chemically-induced mutants were also analysed for protein content and composition. These mutants have previously been shown to display great variation in starch and lipid levels. Total protein varied from 20.3% to 37.9%; however, relative proportions of albumin, legumin and vicilin were similar in all mutant lines. SDS-PAGE analysis identified two mutant pea lines which possessed a legumin A-chain of 65 000 Mras well as the typical 45 000 Mrform. Differential scanning calorimetry of protein extracts indicated that the legumin in all mutants had lower enthalpies of denaturation than the legumin in the round-seeded parent.The mutant pea lines possess exceptional variation with respect to starch, lipid and protein which raises opportunities for their use in the food and animal feedstuff industries.
Chilling injury in germinating seeds: basic mechanisms and agricultural implications
Authors: Bedi Seema , Basra Amarjit Singh 
Published: September 2008

AbstractGerminating seeds of many species, especially those of tropical or subtropical origin, suffer chilling injury when exposed to low but non-freezing temperatures, resulting in poor seedling establishment and reduction in yield. The severity of injury depends upon several factors such as (i) the species or the cultivars involved, (ii) the initial water content of the seed, (iii) the temperature to which seed is exposed, (iv) the duration of chilling exposure and (v) the period during the course of germination when the chilling exposure takes place. The period of imbibition by seeds is the period of sensitivity to the stresses but especially to chilling temperatures. Imbibitional chilling injury is defined as sensitivity to a combination of low seed-water content and imbibition at cold temperature. The mechanism of chilling injury in seeds is different from chilling injury of hydrated tissues and is discussed in relation to the involvement of membranes, respiration, rate of hydration and the concept of discreet moisture levels. Furthermore, the mechanistic and applied aspects of pre-sowing seed treatments for improved germination performance under chilling stress are discussed with an emphasis on hydration-dehydration, osmotic priming and growth regulator treatments.
Conifer seed germination is faster after membrane tube invigoration than after prechilling or osmotic priming
Authors: Downie Bruce , Bergsten Urban , Wang Ben S. P. , Bewley J. Derek 
Published: September 2008

AbstractTwo different pre-emergence treatments preventing radicle protrusion by limiting the extent of imbibition were tested on conifer seeds. Osmotic priming in solutions of polyethylene glycol (PEG) which prevented radicle protrusion during prolonged (3 weeks) treatment resulted in variable percentage germination, mean germination time, and coefficient of uniformity of germination among different seedlots when placed on water. All three germination parameters were either unchanged or inferior in seeds subjected to the various PEG concentrations, treatment temperatures and treatment durations when compared with prechilled controls. In contrast, white spruce and jack pine seeds invigorated at 30% moisture content and 15°C in Gore-Tex membrane tubes consistently germinated faster than prechilled control seeds when subsequently placed on water. Tube invigoration affected neither the ability of seeds to complete germination nor the uniformity of germination. The decrease in mean germination time as treatment duration progressed was always linear and plateaued at approximately 4 days after the tube-invigorated seeds were placed on water regardless of species or seedlot. On average, tube invigoration decreased white spruce mean germination time by 0.13±0.02, and black spruce by 0.23±0.03 day per day of invigoration for up to 20 days of treatment. Jack pine mean germination time decreased 0.2±0.04 day per day of invigoration for up to 14 days of treatment.
Natural and artificial seed ageing in maize: germination and DNA synthesis
Authors: Gutiérrez Germán , Cruz Felipe , Moreno Juan , González-Hernández Victor A. , Vázquez-Ramos Jorge M. 
Published: September 2008

AbstractThe effect of natural and artificial seed ageing has been compared in terms of physiological and biochemical responses of several maize genotypes. The physiological parameters were: viability, germinability, emergence in sand and dry matter accumulation. The biochemical parameters were: DNA synthesis and DNA polymerase activity. A close and direct relationship was found between seed deterioration and DNA metabolism in all maize materials which responded to ageing according to their genetic constitution; i.e., vigorous genotypes suffered less severe damage or recovery was faster than in the low-vigour genotypes. Coordination of events at appropriate times would seem a critical factor for proper seed germination.
The effects of priming on nuclear replication activity and germination of pepper (Capsicum annuum) and tomato (Lycopersicon esculentum) seeds
Authors: Lanteri S. , Saracco F. , Kraak H. L. , Bino R. J. 
Published: September 2008

AbstractUsing flow cytometry, we determined relative DNA amounts expressed as C-values, of large numbers of nuclei isolated from embryo root tips in three seed lots of pepper (Capsicum annuum) and tomato (Lycopersicon esculentum). The nuclei in embryos of fully matured dry pepper and tomato seeds predominantly revealed 2C signals, which indicates that the cells of maturing seeds have arrested at G1 phase of the cell cycle. Priming of pepper and tomato seeds in −1.1, −1.3 or −1.5 MPa polyethylene glycol (PEG) for 14 days reduced the mean time to germination. In all seed lots an induction of 4C signals was found after priming, indicating that during priming the cells of the embryonic root tip had replicated their DNA and arrested at the G2 phase of the cell cycle. For both tomato and pepper, the frequency of 4C signals was highest at the lowest PEG concentration (osmotic potential of −1.1 MPa). A significant inverse correlation was found between the frequency of root tip cells expressing 4C DNA signals and the mean time to germination for each individual pepper and tomato seed lot. However, the effect of a specific osmotic treatment differed between seed lots of the same cultivar, with regard to both the decrease in the mean time to germination and to the percentage of 4C cells, suggesting specific differences among seed lots in the response to priming. The present results indicate that flow cytometry can be used to follow the progress in nuclear replication activities during priming. The advancement in DNA synthesis can thus be used to measure the efficiency of a priming treatment with regard to enhancement of seed lot germination rate.
Differential effects of temperature on ultrastructural responses to dehydration in seeds of Zizania palustris
Authors: Berjak P. , Bradford K. J. , Kovach D. A. , Pammenter N. W. 
Published: September 2008

AbstractThe desiccation tolerance of Zizania palustris seeds has been debatable, but recently it has emerged that survival to low moisture contents is a function of the temperature during dehydration. Survival of dehydration is greatest at 25–30°C and viability declines as the dehydration temperature is reduced. On the other hand, extended hydrated chilling (stratification) is required to break dormancy. The present contribution examines the ultrastructural condition of embryonic axes of Zizania palustris after dehydration at various temperatures, and following reimbibition and stratification. Axis cells sustained least damage when dehydration was carried out at 25°C and ultrastructural deterioration was more severe with lower temperatures during water loss. Damage sustained as a result of unfavourably low dehydration temperatures was visible when seeds were fixed from the dry state and was generally exacerbated during fully imbibed stratification. However, 25°C represented the optimum dehydration temperature; seeds that had been dried at 30°C also showed considerable ultrastructural disturbance when fixed from the dry state. This was largely reversed during fully imbibed stratification, although signs of the damage that had been sustained still persisted. These observations are in keeping with the germination behaviour of Z. palustris seeds dehydrated at temperatures above and below 25°C. The results are discussed in terms of the predominance of one of two mechanisms of membrane deterioration, depending on the dehydration temperature, which are probably not mutually exclusive. It is hypothesized that, at temperatures above 25°C, damage by free-radical-mediated events may predominate, whereas, at temperatures below the optimum, irreversible lipid-phase transitions may be the major factor resulting in membrane damage.
Sucrose and raffinose contents and acquisition of desiccation tolerance in immature maize embryos
Authors: Bochicchio A. , Rizzi E. , Balconi C. , Vernieri P. , Vazzana C. 
Published: September 2008

AbstractWe report preliminary experiments to test the hypothesis that two sugars are involved in the acquisition of desiccation tolerance in immature maize embryos. Sucrose and raffinose were quantified during embryo development, at 16–27 days after pollination (DAP) and during slow dehydration. Embryos were exposed to slow drying either upon excision (18 and 16 DAP) or after an incubation treatment resulting in a decrease in sucrose (18 DAP). The sugars were separated by HPLC with a refractive-index detector; composition was determined by comparing peak areas of interest with those of individual sugar standards. Although further evidence is needed, our results do not appear to support the hypothesis.
Indeterminate development in desiccation-sensitive seeds of Quercus robur L.
Authors: Finch-Savage W. E. , Blake P. S. 
Published: September 2008

AbstractFruit and seed development in Quercus robur L. were studied on a single tree over five consecutive seasons. Patterns of growth in the cotyledons and embryonic axes differed between years and resulted in seeds of very different sizes. Moisture content at shedding also differed between years, and late-shed seeds had lower moisture contents than early-shed seeds. Moisture content at shedding was negatively correlated with desiccation tolerance. Seed development in Q. robur therefore appeared indeterminate and did not end in a period of rapid desiccation.Sensitivity to desiccation in Q. robur was not due to an inability to accumulate dehydrin proteins, ABA or soluble sugars, substances that have been linked with the acquisition of desiccation tolerance in orthodox seeds. There were great similarities between several aspects of Q. robur seed development and that of orthodox seeds before the latter entered the terminal phase of rapid desiccation. This pattern of seed development contrasted with that reported for the highly desiccation-sensitive seeds of Avicennia marina.