bluuebunny/crossref_metadata_2025_split huggingface dataset:
Theoretical basis of protocols for seed storage II. The influence of temperature on optimal moisture levels
Authors: Vertucci Christina W. , Roos Eric E. 
Published: September 2008

AbstractThe premise of this paper is that the chemical potential of water strongly influences aging reactions in seeds, and that there will be an optimal chemical potential of water for seed longevity. If this is true, the optimum moisture content for storage and the optimal drying protocols should vary with the storage temperature, but should be predictable from water sorption isotherms. Isotherms for pea, soybean and peanut are given for temperatures between 65° and −150°C. Relative humidity/moisture content relationships were determined directly for temperatures between 5° and 50°C using saturated salt solutions. At extreme temperatures, isotherms were calculated from heat capacity measurements using differential scanning calorimetry or extrapolations of van't Hoff analyses. The family of isotherms was used to predict optimum moisture contents at storage temperatures between 65°C and −150°C. The optimal moisture contents for these three species are consistently shown to increase as the storage temperature is lowered.
Changes in potential seed longevity and seedling growth during seed development and maturation in marrow
Authors: Demir I. , Ellis R. H. 
Published: September 2008

AbstractMarrow (Cucurbita pepo L.) seed quality was monitored during seed development and maturation in 2 years. Mass maturity (end of the seed-filling phase) was attained 61–63 d and 54 d after anthesis in 1989 and 1990, respectively, when seed moisture contents had declined to 40–48% (wet basis). Considerable dormancy was encountered during standard germination tests, but was overcome by decoating the seeds. The ability of dried, decoated seeds to germinate normally in standard tests reached near maximal values shortly after mass maturity; these values were more or less maintained in seeds from subsequent harvests. Maximum seed longevity in air-dry storage was detected in seeds harvested 24 d (1989) and 26–31 d (1990) after mass maturity. Seedling dry weights 15 d after sowing were greatest for seeds harvested 2–22 d (basal fruits) or 14 d (apical fruits) after mass maturity in 1989, and were positively correlated (P<0.01) with times from seedling emergence to seedling harvest. Consequently in the subsequent year the hypothesis that these differences in seedling dry weight were solely due to differences in times from sowing to emergence was tested (and confirmed). Seedling relative growth rates did not differ with seed harvest date (P>0.25) in 1990, but absolute seedling size did (P<0.005); seeds harvested 21–31 d after mass maturity had the greatest seedling weight and also growth rate (in absolute terms) at any one time after sowing. Decline in seed quality (when assessed by both potential seed longevity and seedling growth) was not detected until the final harvest interval in 1990 (85–90 d after anthesis, 31–36 d after mass maturity). These results for marrow contradict both aspects of the general hypothesis that seed quality is maximal at the end of the seed-filling phase and that viability and vigour begin to decline thereafter.
Carbohydrate concentrations and interactions in afterripening-responsive dormantAvena fatuacaryopses induced to germinate by gibberellic acid
Authors: Foley M. E. , Nichols M. B. , Myers S. P. 
Published: September 2008

AbstractIt has been proposed that gibberellic acid (GA3) promotes germination by overcoming restrictions in sugar production and utilization in afterripening-responsive dormant caryopses. While their germination rates were similar, germination commenced sooner in afterripened wild oat (Avena fatuaL.) caryopses than in dormant caryopses treated with GA3and dormant excised embryos treated with GA3plus fructose (Fru). Limited germination occurred in dormant excised embryos cultured with GA3alone. Carbohydrate concentrations were measured over time in dormant caryopses and excised embryos whose germination was induced with GA3and GA3plus Fru. The concentration of sucrose (Suc) in the endosperm declined prior to germination of dormant GA3-treated caryopses. Raffinose (Raf) family oligosaccharides in the embryos of dormant GA-treated caryopses remained relatively constant prior to and shortly after the onset of germination. In contrast, Raf family oligosaccharides in the embryos of afterripened caryopses declined prior to germination. Together this suggests Raf family oligosaccharide utilization is not associated with germinationper se.Increased starch levels, which occurred in dormant excised embryos treated with Fru and GA3plus Fru, were associated with dormancy because similar effects were not apparent in afterripened embryos cultured with Fru. An initial decline in the concentration of Raf family oligosaccharides in dormant embryos cultured with GA3or GA3plus Fru seems to be a result of the excision process. GA3appears to stimulate the germination of dormant embryos by enhancing the uptake or utilization of Fru. It appears that GA3and afterripening-induced changes in carbohydrate utilization in dormant caryopses are different.
Localization of α-amylase and its inhibitor in germinating wheat seed
Authors: Kanzaki K. , Kawabata C. , Noda Kaz. 
Published: September 2008

AbstractWheat (Triticum aestivumL) seeds contain a proteinaceous α-amylase inhibitor. We estimated the amount of the inhibitor that can bind to α-amylase rather than the total amount of the inhibitor, using an ELISA method. During 48 h of imbibition, the amount of the inhibitor did not change, while α-amylase activity increased rapidly. These results suggest that α-amylase synthesizedde novodoes not bind to the inhibitor. To examine further the interaction between α-amylase and its inhibitor, we localized immunohistochemically both α-amylase and the inhibitor in germinating seeds. In the embryo, we observed α-amylase only in the scutellar epithelial cells at 24 h after the start of imbibition, and later in the scutellar parenchyma cells. The inhibitor, on the other hand, was present between the scutellar parenchyma cells of the embryo at 0 h and 24 h after the start of imbibition, and disappeared later. α-amylase is separated from the inhibitor in the embryo. In the endosperm, we detected α-amylase in the aleurone cells at 24 h after the start of imbibition and later in the starchy endosperm. The inhibitor was present in the aleurone cells and starchy endosperm of the dry seed. During imbibition, the inhibitor in the starchy endosperm disappeared from the area to which α-amylase was secreted. It appears that α-amylase in the starchy endosperm also does not interact with the inhibitor. The aleurone cells are the only place that α-amylase can come into contact with the inhibitor. But, early secretion of α-amylase from the aleurone cells after imbibition started, and rapid disappearance of the inhibitor in the aleurone cells suggest that the α-amylase inhibitor does not work as an effective inhibitor of the endogenous α-amylase synthesized following germination.
Relationship between accumulated hydrothermal time during seed priming and subsequent seed germination rates
Authors: Bradford Kent J. , Haigh Anthony M. 
Published: September 2008

AbstractSeed germination rates are sensitive to both temperature (T) and water potential (ψ). The times to germination of seeds imbibed at suboptimalTand/or reduced ψ are inversely proportional to the amounts by whichTexceeds a base temperature (Tb) and ψ exceeds a base water potential (ψb). Germination rates across a range of suboptimalTand ψ can be normalized on the basis of the hydrothermal time accumulated in excess of these thresholds. However, seeds can also progress metabolically toward germination even atTor ψ too low to allow radicle emergence to occur. Seeds preimbibed at low ψ and dried back, or primed, germinate more rapidly upon subsequent reimbibition. We show here that the increase in germination rates of tomato (Lycopersicon esculentumMill.) seeds resulting from seed priming is linearly related to the hydrothermal time accumulated during the priming treatment. The threshold temperature (Tmin= 7.05°C) and water potential (ψmin= −2.50 MPa) for metabolic advancement were considerably lower than the corresponding thresholds for radicle emergence of the same seed lot (Tb= 11°C; ψb= −0.71 MPa), allowing the accumulation of hydrothermal priming time that is subsequently expressed as more rapid germination whenTor ψ increase. The hydrothermal time model can now be applied to quantify and analyse germination rates of seeds across the entire range of suboptimalTand ψ at which metabolic progress toward radicle emergence is possible.
Hydrothermal time analysis of tomato seed germination at suboptimal temperature and reduced water potential
Authors: Dahal Peetambar , Bradford Kent J. 
Published: September 2008

AbstractBoth temperature (T) and water potential (ψ) have consistent and quantifiable effects on the rate and extent of seed germination (radicle emergence). Germination at suboptimal T can be characterized on the basis of thermal time, or the T in excess of a base (Tb) multiplied by the time to a given percentage germination (tg). Similarly, germination at reduced ψ can be characterized on a hydrotime basis, or the ψ in excess of a base (ψb) multiplied by tg. Within a seed population, the variation in thermal times to germination for a specific percentage (g) is based upon the normal distribution of ψb values among seeds (ψb(g)). Germination responses across a range of suboptimal T and ψ might be accounted for by a general hydrothermal time model incorporating both T and ψ components. We tested this hypothesis for tomato (Lycopersicon esculentum Mill.) seeds of two genotypes differing in germination rates and tolerance of suboptimal T and ψ. For combinations of T (10−25°C) and ψ (0 to −0.9 MPa), a general hydrothermal time model accounted for approximately 75% of the variation in times to germination within the seed populations of both genotypes, and over 96% of the variation in median germination rates. However, ψb(g) distributions were sensitive to both the T and ψ of imbibition, resulting in a poor fit of the model to specific time course data. Analysis of germination timing separately for low and high ψ ranges within a given T resulted in specific models accounting for 88−99% of the variation in individual germination times and >99% of the variation in madian germination rates. Thus, for a given T and ψ range, the hydrotime model closely matched tomato seed germination time courses. Accumulated hydrothermal time accounted well for germination rates at ψ> −0.5 MPa across suboptimal T if ψb(g) was allowed to vary with T. Germination did not show a consistent response to T at ψ < −0.5 MPa, and estimated Tb values varied over different T ranges. Generalization of the hydrothermal time model across the entire range of suboptimal T and ψ was limited by physiological adjustments of the seeds to their current environment. The hydrothermal time model detected and quantified these adjustment processes that would otherwise not be evident from inspection of germination time courses. Temperature and water potential influence the time to germination via physiological mechanisms that reciprocally interact.
Dry matter accumulation into zygotic seed; a model and its application to artificial seeds
Authors: Le Deunff Yvon , Loiseau Jacques 
Published: September 2008

AbstractPea seed development on the mother plant consists of three phases, all limited by water concentration (WC). The first (P1) or embryogenesis sensu stricto takes place at constant WC (stable at 80%). During the phase P2, cotyledon filling or maturation, WC decreases linearly from 80 to 55% (physiological desiccation) but the water content stays constant while the dry weight increases until it stops abruptly (at 55% WC), at this time, the seed has almost reached its final dry weight, its maturity mass or physiological maturity. The third phase, P3, consists of a fast desiccation which leads to a WC of 18–14%, where the seed is mature and ready to harvest. Similar events occur in other grain legumes, in cereals where mass maturity is attained at a lower WC (close to 40%) and in other species including crop or weed species. An elementary model of pea seed dry-matter accumulation, based on the constancy of water content (P1) and the linear decrease of WC from 80 to 55% (P2), allows us to define a coefficient α linked to WC and to calculate dry matter changes versus α. This model, taking account of WC in other species, can be generalized easily. Maturation of the somatic embryo, occurring under conditions very close to those present in vivo around the zygotic embryo, follows a pattern of decrease of WC similar to that of the zygotic embryo. We expect that if cell number is similar in the somatic and the zygotic embryo, synseeds will be ready for trade in the near future since control of all the processes that lead to zygotic-like embryoids is now available.
Leakage of phosphorus and phytic acid from imbibing seeds and grains
Authors: West M. Marcia , Ockenden Irene , Lott John N. A. 
Published: September 2008

AbstractInorganic P, total P and phytic acid-P leakage from imbibing whole soybean, bean, and pea seeds, as well as whole maize and barley grains were measured. The amounts of P and phytic acid leaked during a 6-h soaking period varied for the five species. Soybeans leaked the most P and phytic acid of the species examined. Peas, beans and barley leaked little or no phytic acid. Based on reported levels of total P and phytic acid in the dry seeds/grains that were studied, total P leakage ranged from 0.5 to 1.2%, while phytic acid leakage ranged from 0.01 to 0.5%. No relationship was found between initial levels of total P or phytic acid in the dry seeds/grains and the amount of total P or phytic acid leaked by the imbibed seed/grain. Similarly, the amounts of phytic acid leaked by the seeds/grains of this study did not appear to be related to the water solubility of the phytic acid in the dry seeds/grains.
‘Dehydrin-like’ proteins and desiccation tolerance in seeds
Authors: Gee O. H. , Probert R. J. , Coomber S. A. 
Published: September 2008

AbstractThe relationship between tolerance of seeds to extreme desiccation and the presence of ‘dehydrinlike’ proteins was investigated in groups of related taxa from the unrelated plant families Aceraceae and Gramineae. Dehydrin-like proteins were identified by Western blot analysis using an antibody raised against a synthetic oligopeptide representing the 23-amino acid consensus sequence common to all group 2 late-embryogenesis-abundant (LEA) proteins.Evidence is presented that seeds of Acer pseudoplatanus and A. saccharinum are desiccation intolerant (recalcitrant) whereas seeds of A. platanoides and A. rubrum are desiccation tolerant (orthodox). Despite these differences, dehydrinlike proteins at 60 and 20 kDa were detected in all four species.Dehydrins at 20 kDa were also detected in seed samples of two aquatic grasses, Porteresia coarctata and Oryza sativa from the tribe Oryzeae, despite seeds of the former rapidly losing viability on drying, whereas O. sativa is one of the best-known examples of desiccation-tolerant seeds. In O. sativa, there was a correlation between contents of dehydrins detected and the proportion of individuals capable of withstanding extreme drying. However, the possibility of a causal link between these parameters is equivocal. Dehydrin-like proteins were also detected in desiccation-sensitive seeds of Zizania palustris, Z. latifolia and Z. texana and desiccation-intolerant seeds of Spartina anglica, all from the Gramineae.The presence of group 2 LEAs is clearly not diagnostic of desiccation tolerance in seeds. However, a more direct correlation with the expression of other groups of LEAs cannot be discounted.
Changes in soluble sugars in relation to desiccation tolerance in cauliflower seeds
Authors: Hoekstra F. A. , Haigh A. M. , Tetteroo F. A. A. , van Roekel T. 
Published: September 2008

AbstractChanges in soluble sugars in cauliflower seeds were followed during 50 h of imbibition in relation to desiccation tolerance. Sucrose and stachyose contents decreased, and glucose and fructose accumulated. This occurred in radicles first and subsequently in hypocotyls and cotyledons. Loss of desiccation tolerance in the various seed parts coincided with an increase in glucose and fructose and the complete loss of stachyose, but sucrose content, the major sugar, was still high. Drying imbibed seeds over silica gel did not evoke resynthesis of stachyose, but did increase sucrose and decrease glucose and fructose contents. Seeds primed in solutions of 30% polyethylene glycol for 10 days showed a loss of stachyose, while sucrose remained high and glucose and fructose contents were still very low. Redrying of primed seeds did not change the sugar contents. The primed seeds were still tolerant of desiccation. We conclude that stachyose is not a prerequisite for desiccation tolerance, but that sucrose may be. We suggest that glucose and fructose may be involved in desiccation damage.
Role of desiccation in the termination of expression of genes for storage proteins
Authors: Jiang L. , Kermode A. R. 
Published: September 2008

AbstractThe final stage of development of orthodox seeds is maturation drying, a process often accompanied by a dramatic decline in storage-protein synthesis. When desiccation is imposed prematurely at certain stages prior to the completion of development, a switch in synthetic events is elicited. events unique to development, such as synthesis of storage protein, are terminated, while syntheses associated with germination and growth are initiated. We investigated whether desiccation plays a key role in effecting a decline in expression of genes for storage proteins by acting directly upon the regulatory regions of these developmental genes. The desiccation responsiveness of the 5′ and 3′ regulatory regions of the gene for the pea storage protein vicilin was tested in transgenic tobacco seed. Chimaeric genes were introduced into tobacco, these genes consisted of the coding region of the reporter gene for β-glucuronidase (GUS) and 5′ and 3′ regions from the vicilin gene, or, as controls, the same regions derived from constitutively expressed genes, presumed to be desiccation-insensitive – those from the cauliflower mosaic virus (35S) and nopaline synthase genes. In transgenic seed expressing the gene constructs containing the vicilin 5′ upstream region, GUS activities declined dramatically after imbibition in mature seed and after rehydration of prematurely dried tobacco seed. In contrast, GUS activities increased after seed rehydration when the constitutive viral (35S) promoter replaced the vicilin 5′ upstream region. The 3′ downstream region of the gene construct did not significantly affect the patterns of changes in GUS activities after seed rehydration. In studies of transient gene expression in castor bean cotyledons, premature desiccation led to termination ofGUSgene expression only when the gene construct contained the vicilin 5′ upstream region. This region may respond directly to desiccation; alternatively, changes totrans-acting factors important for expression of genes for storage-proteins may occur as a result of drying.
DNA and desiccation tolerance
Authors: Osborne D. J. , Boubriak I. I. 
Published: September 2008

AbstractThis article reviews mechanisms by which specialized cells of different life forms have overcome the lethal effects of dehydration and considers how the maintenance of genetic information is central to survival. As a dynamic and hydrated moleculein vivo, DNA can assume different conformational structures depending upon the water activity, the base sequence and the presence of specific binding proteins. The attainment of stable secondary structures that are resistant to degradationin vivoat low water potentials is proposed as a likely accompaniment to desiccation tolerance. In addition, chemical modification of bases in DNA, the extent of methylation and conformational changes could determine the expression of different gene sequences as cells pass from desiccation-tolerant to desiccation-intolerant states. We monitored the integrity of extracted DNA in embryos of seeds and in wind-dispersed pollen during transition from their desiccation tolerance to desiccation intolerance on hydration and germination. We present evidence to show that the DNA of these two stages is different and that it is the DNA from desiccation-tolerant cells only that retains integrity when the cells are subjected to desiccation regimes. We discuss these findings in relation to certain hydration-sensitive DNA structures and to other relevant biological systems.
Why do stored hydrated recalcitrant seeds die?
Authors: Pammenter N.W. , Berjak P. , Farrant J.M. , Smith M.T. , Ross G. 
Published: September 2008

AbstractA characteristic of recalcitrant seeds is that, if they are maintained under storage conditions that prevent water loss, they will ultimately lose viability. A current view is that hydrated recalcitrant seeds are metabolically active and undergo germination-associated changes in storage. Some of these changes, such as extensive vacuolation and increase in cell size, imply a requirement for water additional to that present in the seed on shedding. It is therefore suggested that, in storage, recalcitrant seeds are exposed to an initially mild, but increasingly severe, water stress. Deleterious events associated with a water stress of considerable duration are suggested to lead ultimately to the death of the tissue.The damage that occurs on prolonged storage is unlikely to be associated with an inability to form glasses or prevent membrane lipid phase changes, as absolute water contents are higher than those at which these mechanisms become important. It is considered that the most likely process leading to death of water-stressed (as opposed to dehydrated) tissue is a breakdown of co-ordination of metabolism, leading to uncontrolled free-radical-mediated oxidative damage.It is generally difficult to maintain tissue in a mild water-stressed condition for extended periods. Stored, hydrated, recalcitrant seeds may provide an ideal model system for studying the metabolic effects of prolonged mild water stress.
Effect of abscisic acid and slow drying on soluble carbohydrate content in developing embryoids of carrot (Daucus carota L.) and alfalfa (Medicago sativa L.)
Authors: Tetteroo F. A. A. , Bomal C. , Hoekstra F. A. , Karssen C. M. 
Published: September 2008

AbstractIn the presence of abscisic acid (ABA), contents of glucose and fructose decreased in carrot embryoids, whereas umbelliferose increased during dehydration. The acquisition of desiccation tolerance was tested by scoring germinated embryoids. It did not keep pace with the changes in soluble carbohydrate contents during development, which suggests that in these somatic embryoids di- and oligosaccharides are not the determining factors for anhydrobiosis. However, on slow dehydration, umbelliferose increased, while sucrose decreased and the monosaccharides declined completely. These changes were positively correlated with increased desiccation tolerance. A similar analysis of slowly dried, ABA-treated alfalfa embryoids showed that stachyose and sucrose increased and the monosaccharides declined with the acquisition of desiccation tolerance. These data support the contention that carbohydrates are involved in anhydrobiosis.