bluuebunny/crossref_metadata_2025 huggingface dataset:
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

It 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

Wheat (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

Seed 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

Both 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

Pea 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

Inorganic 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

The 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

Changes 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

The 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

This 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

A 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

In 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.
Expression of ‘dehydrin-like’ proteins in orthodox seeds ofRanunculus sceleratusduring development and water stress
Authors: Wechsberg G. E. , Bray C. M. , Probert R. J.
Published: September 2008

Western blot analysis using antiserum raised against the lysine-rich box common to dehydrins, one class of late-embryogenesis-abundant (LEA) proteins, was used to study the abundance of heat-stable ‘dehydrin-like’ proteins during development and water stress inRanunculus sceleratusL. achenes (seeds). A 61 kDa dehydrin-like protein was apparently limited to immature seeds (fresh and dried) which had not attained full desiccation tolerance. In contrast, lower-molecular-mass proteins which were induced by desiccation were found only in more mature seeds. The molecular masses of desiccation-induced proteins changed during seed development from 18 kDa in seeds harvested at 13 days post anthesis (DPA) to 31 kDa at harvest maturity, 21 DPA.

Placing seeds at 21 DPA in polyethylene glycol (PEG) at −1.5 MPa reduced seed moisture content and was accompanied by accumulation of 31 kDa protein. This protein was no longer detected when the seeds were transferred to water. In seeds harvested at 13 DPA, PEG induced the synthesis not only of 18 kDa protein (which is associated with dried seeds at this developmental stage), but also of 28 kDa and 31 kDa proteins. These dehydrin-like proteins were also synthesised when seeds at 13 DPA were imbibed in water. These and other data indicate that both quantitative and qualitative changes in dehydrin-like proteins can occur inR. sceleratus, depending on seed maturity and the degree and duration of water stress.
The glassy state in seeds: analysis and function
Authors: Leopold A. Carl , Sun Wendell Q. , Bernal-Lugo Irma
Published: September 2008

In view of the finding that dry seeds may exist in the glassy state, a brief review of the commonest methods of detection and quantification of the glass transition is presented. While the glassy state may contribute to seed tolerance of desiccation, it does not appear to account for desiccation tolerance. Its major function in dry seeds may be its contribution to the stability of the seed components during storage.
Effect of various sugars and polyols on the tolerance to desiccation and freezing of oil palm polyembryonic cultures
Authors: Dumet D. , Engelmann F. , Chabrillange N. , Dussert S. , Duval Y.
Published: September 2008

During a 7-day conditioning treatment of clumps of oil palm (Elaeis guineensis Jacq.) somatic embryos on a medium containing 0.75 M sucrose, the fructose and glucose concentrations remained constant, whereas a ten-fold and twenty-fold increase were noted for sucrose and starch concentrations, respectively. The only new sugar detected was arabinose which remained at a low concentration. After conditioning on media supplemented with various sugars and polyols at similar osmolarities, recovery of clumps of embryo growth was satisfactory except with ribose. After an additional desiccation period, survival was optimal with fructose, galactose, sucrose and glucose, intermediate with maltose and lower with other compounds. When embryos were cryopreserved without previous desiccation, survival was noted after conditioning treatment with sucrose only. In contrast, when freezing was performed after dehydration, survival could be obtained with several substances. It was optimal with sucrose, fructose, galactose and raffinose but was possible also with sorbitol and glucose. Intensity of recovery of proliferation was highest with embryos conditioned with sucrose.
Water relations of germination in the recalcitrant seeds of Quercus robur L.
Authors: Finch-Savage W. E. , Clay H. A.
Published: September 2008

Quercus robur L. fruits are desiccation sensitive and shed from the plant at high moisture content (c. 48%). Water relations measurements were taken at intervals during the germination of prematurely-harvested immature fruits and naturally-shed mature fruits. In fruits from both harvests the pericarp and seed coat delayed germination by providing physical barriers to emergence of the radicle and by restricting the rate of imbibition. Although immature fruits could germinate in the absence of water they germinated more rapidly in the presence of an external water supply. The fully-mature fruit required a supply of external water, but germination was more rapid than in immature fruits. Substantial physiological changes, resulting in the accumulation of solutes, and increased axis size and extensibility occurred before splitting of the pericarp and subsequent germination of immature fruits. Such changes did not occur in fully-mature fruits, but fruits, from both harvests imbibed water and splitting of the pericarp appeared to result from increased embryo size and tissue pressure. Splitting was minimal prior to germination in immature fruits without an external water supply. It is suggested that the resulting reduction in Ψp when the pericarp splits was greater in the axis than in the cotyledons because of its greater capacity for expansion. This would create a Ψw gradient driving water flow to the axis from the cotyledons allowing continued radicle growth for germination.
Characterization of serine proteinase inhibitors in dry seeds of cultivated pasture grass species
Authors: Tasneem Mohammed , Cornford Clive A. , McManus Michael T.
Published: September 2008

A survey of proteinaceous inhibitors of the serine proteinases, bovine trypsin and chymotrypsin, that are extractable from dry seeds of several cultivars of pasture grasses has been undertaken. Using crude extracts, most cultivars screened contained inhibitors of chymotrypsin, whereas trypsin inhibition was not detectable. Seeds from four cultivars,Lolium perenneL. cv. Grasslands Ruanui,Lolium×boucheanumcv. Grasslands Greenstone,Festuca arundinaceaSchreb. cultivars Grasslands Roa and Grasslands Garland, that contained more potent chymotrypsin inhibition were purified further. After gel filtration chromatography, both trypsin and chymotrypsin inhibition could be observed in all four cultivars, and each separated into two discrete native molecular weights; one ofca.20–22 kDa and one ofca.8–10 kDa. However, activity staining, after polyacrylamide gel electrophoresis, revealed an array of iso-inhibitors with molecular weights that ranged fromca.3 kDa to 20 kDa. One of these, a dual trypsin/chymotrypsin inhibitor ofca.12 kDa that is present in all four cultivars examined, was purified to homogeneity fromF. arundinaceacv. Grasslands Garland using anhydro-trypsin affinity chromatography and reverse-phase HPLC. The protein was found to comprise two closely related peptides and N-terminal amino acid sequencing revealed highest identity with a trypsin inhibitor identified in rye (Secale cereale) seeds.
Use of low temperature scanning electron microscopy to observe frozen hydrated seed tissues ofGlycine max
Authors: Yaklich Robert W. , Wergin William P. , Erbe Eric F.
Published: September 2008

Evidence is provided to show that frozen, hydrated seeds and seed tissues can be observed by low temperature field emission scanning electron microscopy. This technique allows preparation and observation of seed samples that contain 13–60% water without altering their moisture content. The technique provides information about the surface structure of seeds and also allows specimens to be fractured to reveal internal features of tissues. Futhermore, both halves of fractured specimens can be retained, examined and photographed either as two-dimensional micrographs or as stereo pairs when three-dimensional observation (stereology) or quantitative measurements (stereometry) are desired. Use of this technique avoids artefacts associated with chemical fixation, dehydration, and critical point drying—procedures that are usually required to prepare seed tissues for scanning electron microscope examination. This technique does not affect the degree of hydration in specimens; it can be used to localize water in tissues to determine their degree of hydration. This technique should find wide application in developmental studies of seeds, especially during maturation, imbibition and germination.
Seed desiccation tolerance and storability: Dependence on flatulence-producing oligosaccharides and cyclitols—review and survey
Authors: Horbowicz Marcin , Obendorf Ralph L.
Published: September 2008

Stachyose, raffinose and related flatulence-producing oligosaccharides (α-galactosyl derivatives of sucrose) are associated with desiccation tolerance and storability of seed germplasm. Orthodox seeds of species with a sucrose-to-oligosaccharide ratio of <1.0 have storability half-viability periods >10 years while those >1.0 have a storability half-viability period <10 years. Seeds vary in their composition of oligosaccharides and some accumulate α-galactosyl derivatives of cyclitols. Known and proposed pathways for biosynthesis of soluble oligosaccharides, cyclitols and galactosyl derivatives of cyclitols are presented. Axes, cotyledons, embryos or seeds of 19 species in 7 families (all orthodox seeds) were analysed for sucrose, galactosyl derivatives of sucrose, cyclitols and galactosyl derivatives of cyclitols by high resolution gas chromatography. Sucrose andmyo-inositol are universally present and galactinol is present in seeds accumulating stachyose series oligosaccharides. Seeds of some species of Leguminosae accumulate mostly stachyose series oligosaccharides, whereas seeds of other species accumulate varying levels of galactosyl derivatives of cyclitols in addition. Castor bean (Euphorbiaceae) seeds accumulate galactinol and buckwheat (Polygonaceae) embryos accumulate galacto-chiro-inositol instead of the stachyose series oligosaccharides. The mass ratio of sucrose:non-sucrose is related to storability and is applicable to seeds accumulating cyclitol derivatives. Galactinol and galacto-chiro-inositol are proposed to function in the same role as raffinose and stachyose in facilitating desiccation tolerance and storability.
Induction of desiccation tolerance in germinated seeds
Authors: Bruggink Tonko , van der Toorn Peter
Published: September 2008

The induction of desiccation tolerance in germinated seeds by incubation in PEG for several days is reported. The induction coincided with an increased sucrose content and the formation of heat-soluble proteins. Germinated seeds can serve as a convenient model system in studies of desiccation tolerance. This finding may have important implications for the agricultural industry.
Biochemical and cytological studies on osmoprimed maize seeds
Authors: García Felipe Cruz , Jiménez Luis F. , Vázquez-Ramos Jorge M.
Published: September 2008

The conditions of osmopriming of maize seeds have been established. At an osmotic potential of–1.7 MPa, seed germination is inhibited and seeds osmoprimed for up to 3 weeks show an improved germinability when the osmotic agent is removed. This improvement also applies to seeds that lost vigour because of improper storage conditions. At the biochemical level, embryo axes from osmoprimed seeds can incorporate precursors into DNA, RNA and proteins although at a low level; after removing the osmotic agent, all 3 types of macromolecules are synthesized at much higher levels. No evidence of DNA replication or cell division was found during osmopriming; however, mitotic figures appear several hours earlier in germinated, osmoprimed root tissues compared with the time at which they appear in non-osmoprimed tissues. The behaviour of osmoprimed maize is compared with that of osmoprimed seeds from other plant species.
Influence of priming-induced nuclear replication activity on storability of pepper (Capsicum annuumL.) seed
Authors: Saracco F. , Bino R. J. , Bergervoet J. H. W. , Lanteri S.
Published: September 2008

The effect of two priming treatments in PEG solutions on nuclear replication stages of pepper (Capsicum annuumL.) embryos were evaluated using flow cytometry. Priming at −1.1 MPa for 10 d induced almost 40% of nuclei in the embryo root tips to enter the synthetic phase of nuclear division, while no DNA synthesis occurred during 6 d at−1.5 MPa and in less than 10% of the nuclei at 10 d. Both priming treatments effectively increased seed performance. A decrease of 2.7 d in mean germination time (MGT) was observed after priming in PEG solution at −1.1 MPa, while the treatment at−1.5 MPa lowered the MGT by 2.1 d. Primed and untreated seeds were subjected to controlled deterioration treatments by exposure to 45°C after equilibration at 75% RH. Both osmotic treatments considerably lowered seed tolerance to adverse storage conditions as compared with untreated seeds. However, seeds in which DNA replication was induced by priming were more sensitive to controlled deterioration than seeds in which priming did not induce nuclei to enter the synthetic phase. This could be a consequence of a higher DNA content, which is a more vulnerable target for mutation inducing factors. Alternatively the increased sensitivity could be a consequence of their more advanced progress in germinative events, making seeds less resistant to deteriorative factors imposed during storage. On the whole, from the present results it appears that the nucleic acid DNA content of the embryo only plays an additive role in influencing seed storability.
Comparative biochemical and morphological changes in imbibed cotton seed hypocotyls and radiclesin situandin vitro– Protein breakdown and elongation growth
Authors: Vigil Eugene L. , Fang Tung K.
Published: September 2008

Axes, hypocotyls and radicles excised from dry cotton seeds (Gossypium hirsutumL. cv. M-8, a double haploid) were imbibed for 24 h and compared with axial segments (excised sections of embryos below the cotyledons) of imbibed, intact seeds. Radicles of excised axes had a 7.4-fold increase in length compared with only 5.2- and 5.7-fold increases, respectively, in radicles of intact seeds and in those isolated when dry. Change in hypocotyl length was not as extensive. EM data for hypocotyl and radicle cortical cells from dry and imbibed seeds revealed a major reduction in matrix protein in protein storage vacuoles along with significant organelle development at 24 h from the start of imbibition. This occurred in parallel with a reduction in salt-extracted proteins and an increase in 2% SDS-extractable proteins. SDS-PAGE of protein from low (0.2 M NaCI) and high (1.0 M NaCI) salt extracts showed a reduction in amount of the major storage proteins (53 and 48 kDa), these bands being almost totally absent in gels of protein extracts from imbibed radicles and significantly reduced in hypocotyls, within 24 h from the start of imbibition. These results indicate that initial elongation of hypocotyls and radicles in intact seeds or of excised axes, after 24 h imbibition, involves breakdown of storage proteins in these axial parts to supply nutrients for growth, with very limited contribution from the cotyledons.
Cryopreservation of zygotic embryos and kernels of oil palm (Elaeis guineensis Jacq.)
Authors: Engelmann F. , Chabrillange N. , Dussert S. , Duval Y.
Published: September 2008

In the present study, the efficiency of two cryopreservation strategies for oil palm (Elaeis guineensis Jacq.) was compared. If extracted from rehydrated kernels, 65% of the embryos desiccated to around 0.3 g H2O/g DW developed into plantlets after cryopreservation. In contrast, only 25% of embryos (0.12 g H2O/g DW) extracted from cryopreserved dry kernels developed into plantlets. However, this value was increased to 63% if kernels were partially rehydrated before freezing until the water content of embryos reached 0.3 g H2O/g DW. This study emphasizes the importance of partial rehydration of oil palm embryos before cryopreservation.
Environmentally induced polymorphisms detected by RAPD analysis of soybean seed DNA
Authors: Shatters Robert G. , Schweder Mark E. , West S. H. , Abdelghany Ashraf , Smith Rex L.
Published: September 2008

Experiments were performed to determine if RAPD profiles developed using total DNA isolated from soybean seed could be affected by the physiological state or the quality of the seed. RAPD profiles were developed using template DNA isolated from a single seed lot of soybean (Glycine max L. cv. Kirby). High quality seeds were used to produce four populations varying in either quality or physiological state: untreated control seed ambient temperature and humidity storage for 12 months, accelerated aging at 41°C and 100% relative humidity for 48 h, and controlled hydration (seed priming). One hundred and eighty-eight primers were used to create separate RAPD profiles from total DNA isolated from each set of seed and from soybean leaf tissue. Sixteen polymorphisms from 14 primers were identified as a result of seed treatments. Six primers showed nine polymorphisms in RAPD profiles of ambient-stored seed DNA, while four and two primers produced polymorphisms in reactions using accelerated aged or primed-seed template DNA, respectively. Two primers showed a polymorphic fragment in vegetative DNA not observed in any of the seed DNA samples. Ten of the observed polymorphisms were due to the appearance of a DNA fragment in response to a specific seed treatment while six were the result of the treatment-induced loss of a DNA fragment. The six polymorphisms resulting from the loss of a major fragment were all due to ambient-temperature seed storage. Results were reproducibly obtained from multiple DNA isolations using three separate DNA isolation procedures involving either multiple seed or a single seed as the template source. Therefore, genetically identical seed can consistently display RAPD polymorphisms as a response to the environmental exposure.
Changes in glass transition temperatures in germinating pea seeds
Authors: Williams Robert J. , Leopold A. Carl
Published: September 2008

An element of storage stability of many orthodox seeds is that the embryo cytoplasm is vitreous at normal storage temperatures. That is, as drying proceeds during seed maturation, intracellular solutions become so concentrated and viscous that diffusional movement is all but eliminated (Williams and Leopold, 1989). In this report the relationship between desiccation tolerance and the ability to form the vitreous state as germination proceeds is examined. As pea seeds (Pisum sativum cv. Alaska) imbibed water up to 18 h, no change in the glass transition temperature was seen, and the embryos remained desiccation-tolerant. Between 18 and 44 h of imbibition, the axes lost the ability to exhibit a distinguishable vitreous transition, and the embryos had lost the ability to survive desiccation. After about 50 h, embryos again showed vitrification but only at markedly lower temperatures, as would be expected to accompany the loss of oligosaccharides (sucrose, raffinose, stachyose and verbascose) and their replacement by monosaccharides during early germination (Koster and Leopold, 1988). Thus, the loss of desiccation tolerance during germination in pea seeds appears to be associated with a loss of the high temperature oligosaccharide: water glass and a subsequent appearance of a new glass transition at a lower temperature resulting from the accumulation of monosacchrides.
Effects of production factors on germination responses of carrot seeds to temperature and oxygen
Authors: Corbineau F. , Picard M. A. , Bonnet A. , Côme D.
Published: September 2008

Various sources of germination heterogeneity of carrot (Daucus carotaL.) seeds were investigated: germination conditions (temperature, oxygen tension), size of seeds, position of the umbels on the mother plants, and pollination conditions of male-sterile plants in hybrid seed production. All seeds tested germinated over a large range of temperatures (5–35°C). However, low temperatures (5–10°C) and temperatures above 30°C reduced germination. Seeds were also sensitive to oxygen deprivation, but their sensitivity to hypoxia depended on the cultivar. The germination responses of seeds to temperature and oxygen depended on their size, particularly at sub- and supra-optimal temperatures. The largest seeds (1.8–2.1 mm) of commercial lots usually germinated better at 5°C and were more sensitive to oxygen deprivation than the smallest ones (1.2–1.8 mm). Experiments performed with open pollinated plants showed that seeds produced by umbels of first and second orders germinated faster and at higher percentages than those collected on third-order umbels. Evidence for the involvement of pollination conditions in the germination quality of carrot seeds was given by pollination by honey bees of male-sterile plants cultivated at various distances from the pollen donors. The longer the distance of the mother plants from the pollinating plants, the lower the seed yield, the heavier the mean seed weight, the more difficult the germination of seeds, and the higher their sensitivity to oxygen deprivation.
Isolation and characterization of a heat-soluble protein from pea (Pisum sativum) embryos
Authors: Russouw Pauline S. , Farrant Jill , Brandt Wolf , Maeder Dennis , Lindsey George G.
Published: September 2008

An LEA-like protein has been isolated and characterized from pea (Pisum sativum) embryos. It is the most prevalent protein in a homogenate of pea axes heated for 10 min at 80°C and then centifuged for 10 min at 17000g(80°C supernatant fraction). It has a molecular mass of 11 kDa and is very rich in hydrophilic amino acids, notably aspartate, glutamate and glycine. The protein is not recognized by an antibody to the group II dehydrin C-terminal consensus sequence. Antibodies to the isolated protein recognize a number of larger proteins in the 80°C supernatant fraction of pea and other legumes (chick pea, soybean and bean) as well as gramineous seeds (wheat, maize and barley). The protein undergoes a substantial increase in α-helical content at high ionic strength but does not dimerize.
Seed stratification and germination strategy in the Mediterranean pines Pinus brutia and P. halepensis
Authors: Skordilis Antonis , Thanos Costas A.
Published: September 2008

The ecophysiology of germination in Pinus brutia and P. halepensis was studied in seeds collected from different areas of Greece. In regard to the temperature range of germination, both P. halepensis and the southern provenance (Lasithi, Crete) of the East Mediterranean pine, P. brutia, follow a typical Mediterranean pattern. In the latter species, dramatic differences in the degree of dormancy were noted among the three provenances investigated; in all seed lots however, 20°C was clearly the optimal temperature for germination. Stratification resulted in a considerable promotion of P. brutia seed germination. Nevertheless, the inductive effect of stratification was shown to differ among the three provenances used, escalating from a simple increase of germination rate (in the southern seed lot from Lasithi, Crete) through a broadening of the temperature range of germination (in the intermediate lot from Thasos Island) to, finally, a dramatic release from a particularly deep dormancy (in the northern lot from Soufli). These deeply dormant seeds of the latter provenance displayed an absolute stratification requirement; prolonged illumination or seed coat scarification could not substitute for the promotive effect of prechilling. A considerable interaction between far-red light and stratification was revealed in the dormant seeds of P. brutia (Soufli provenance); far-red pulses during stratification could either cancel or diminish the germination promotion induced by low temperatures. The differences observed in the germination behaviour among the various P. brutia provenances may be attributed to a variable ecophysiological strategy in regard to the temporal pattern of seedling emergence and establishment. According to the variants of this strategy, seed germination is timed to occur during either spring (in regions with relatively cold and moist climates), or autumn and early winter (in southern, mild and dry areas) or both (in intermediate conditions).
Ecophysiology of germination in the aromatic plants thyme, savory and oregano (Labiatae)
Authors: Thanos Costas A. , Kadis Costas C. , Skarou Flora
Published: September 2008

Ecophysiological aspects of seed germination were investigated in the widely distributed Mediterranean-endemic, aromatic plants thyme (Coridothymus capitatus), savory (Satureja thymbra) and oregano (Origanum vulgaresubsp.hirtum). Thyme seed germination is light indifferent, whereas oregano seeds have an absolute light requirement; their germination can be promoted even by green safelight or far-red light. In savory, a portion of the seeds germinates in the dark and germination can be either increased or decreased by the appropriate illumination. All three species show more germination at a relatively low temperature range, a Mediterranean characteristic, with an optimum around 15–20°C. The rate of germination is considerably higher in the tiny seeds of thyme and oregano than in the larger seeds of savory. In the latter species, germination is also dependent upon the age of the seeds; old seeds germinate to a higher percentage than fresh ones, as already observed by Theophrastus, possibly as a result of the volatilization of the essential oils present on the nutlet coat. Seeds of thyme, savory and oregano are dispersed within the persistent fruiting calyces and the seeds eventually germinate within it. Essential oils in the calyx strongly inhibit germination of the enclosed seeds; germination is much suppressed in thyme and to a lesser extent in savory and oregano. This diaspore dormancy caused by essential oils apparently is overcome under natural conditions by leaching of the inhibitors with rainwater. It is suggested that this dormancy operates as an adaptation strategy that delays germination by acting as a rain gauge. In this way, seed germination and subsequent seedling establishment are prevented during the early phase of the rainy period, which is usually interrupted by drought spells in the Mediterranean climate.
Molecular studies on osmoprimed seeds of cauliflower: a partial amino acid sequence of a vigour-related protein and osmopriming-enhanced expression of putative aspartic protease
Authors: Fujikura Yuzo , Karssen Cees M.
Published: September 2008

A partial amino acid sequence of a vigour-related protein, V-1, from cauliflower (Brassica oleracea L.) seeds was obtained, after isolation by two-dimensional gel electrophoresis and gas-phase micro-sequencing. The sequence was found to have high homology to soybean seed maturation proteins. However, the position of the sequence in the V-1 polypeptide suggests that the V-1 and soybean proteins have different polypeptide structures. An osmoprimed seeds cDNA library was constructed and has been screened by a cDNA probe derived from the V-1 sequence. Two cDNA clones with high homology to aspartic protease (EC 3.4.23) from barley grain were isolated. The expression of putative aspartic protease mRNA was found to be enhanced by osmopriming, however the clones were found to have no significant sequence homology to the V-1.