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At least 19 recordsLinked to original sources
PubMed1995

Seed Dormancy in Red Rice (Oryza sativa) (IX. Embryo Fructose-2,6-Bisphosphate during Dormancy Breaking and Subsequent Germination).

Fructose-2,6-bisphosphate (Fru-2,6-bisP) was evaluated as a potential marker for the dormancy-breaking phase or the germination phase before pericarp splitting in red rice (Oryza sativa). During 4 h of imbibition at 30[deg]C, Fru-2,6-bisP of dehulled dormant and nondormant seeds increased to 0.26 and 0.38 pmol embryo-1, respectively. In nondormant seeds, embryo Fru-2,6-bisP content remained stable until the onset of pericarp splitting (12 h) and increased rapidly thereafter. In dormant seeds, Fru-2,6-bisP declined to 0.09 pmol embryo-1 at 24 h. Embryo Fru-2,6-bisP was correlated with O2 uptake of dormant and nondormant seeds. A 24-h exposure of dehulled, water-imbibed, dormant seeds to treatments yielding >90% germination (sodium nitrite [4 mM], propionic acid [22 mM], methyl propionate [32 mM], propanol [75 mM], and propionaldehyde [40 mM]) led to changes in embryo Fru-2,6-bisP that were unrelated to the final germination percentages. Furthermore, a 2-h pulse of propionaldehyde increased Fru-2,6-bisP 4-fold but did not break dormancy. Whereas nitrite and propionaldehyde increased Fru-2,6-bisP to 0.33 pmol embryo-1 after 2 h of contact, propionic acid and methyl propionate did not increase Fru-2,6-bisP above the untreated control. In all cases, further increases in Fru-2,6-bisP occurred after pericarp splitting. However, the plateau Fru-2,6-bisP attained during chemical contact was inversely correlated with elapsed time to 30% germination (r = -0.978). Therefore, although Fru-2,6-bisP is not a universal marker for dormancy release, its rapid increase during nitrite and propionaldehyde treatments suggests that events associated with dormancy breaking can occur within 2 h of chemical treatment.

Journal Article↗
PubMed1967

Seed dormancy: breaking by uncouplers and inhibitios of oxidative phosphorylation.

When 2,4-dinitrophenol and carbon dioxide were applied together to dormant seeds of Trifolium subterraneum L. (subterranean clover), 2,4-dinitrophenol did not disturb the breaking of dormancy which carbon dioxide usually induces in legume seeds. On the contrary, on its own, it promoted germination in a substantial proportion of seeds; a similar effect was produced by other uncouplers or inhibitors of oxidative phosphorylation.

Antimetabolites↗
PubMed1992

Seed Dormancy in Red Rice : VIII. Embryo Acidification during Dormancy-Breaking and Subsequent Germination.

Exposure of dehulled, dormant red rice (Oryza sativa) seeds to dormancy-breaking treatments (10 mm sodium nitrite, 20 mm propionic acid, 30 mm methyl propionate, 40 mm propionaldehyde, or 70 mmn-propanol) induced tissue pH acidification during chemical contact at least 12 h before visible germination. During chemical contact, the onset of embryo acidification occurred before or coincident with the chemical contact interval necessary for subsequent germination. Upon seed transfer to H(2)O following chemical contact, embryo pH also decreased coincident with visible germination. During this period, the percentage of germination and embryo pH were closely linked irrespective of the dormancy-breaking compound used. Therefore, tissue acidification during the breaking of seed dormancy and the germination process may be analogous to similar tissue pH changes associated with the termination of developmental arrest in other multicellular systems, such as brine shrimp cysts and nematode larvae.

Journal Article↗
PubMed2004

Changes in histone H3 and H4 multi-acetylation during natural and forced dormancy break in potato tubers.

The effects of post-harvest storage and dormancy progression on histone acetylation patterns were examined in potato (Solanum tuberosum L. cv. Russet Burbank) tubers. Storage of field-grown tubers at 3 degrees C in the dark resulted in the progressive loss of tuber meristem dormancy, defined as measurable growth after transfer to 20 degrees C for 7 days. Dormancy emergence was concomitant with sustained increases in histone H3.1 and H3.2 multi-acetylation, and with transient increases in H4 multi-acetylation that peaked 4-5 months post-harvest. Treatment of dormant tubers with bromoethane (BE) resulted in rapid loss of dormancy over 9 days. Similar to cold-stored field-grown tubers, dormancy break in BE-treated tubers occurred at the same time as transient rises in H4 and H3.1/3.2 multi-acetylation, peaking at days 1 and 4, respectively. BE treatment also resulted in small increases in RNA synthesis at day 6, and a three-fold, sustained activation of DNA synthesis thereafter. A defined sequence of epigenetic events, beginning with previously characterized transient cytosine demethylation, followed by increased H3 and H4 histone acetylation and ultimately, tuber meristem re-activation, may thus exist in potatoes during dormancy exit and resumption of rapid growth.

Journal Article↗
PubMed2005

Gene expression analysis by cDNA-AFLP highlights a set of new signaling networks and translational control during seed dormancy breaking in Nicotiana plumbaginifolia.

Seed dormancy in Nicotiana plumbaginifolia is characterized by an abscisic acid accumulation linked to a pronounced germination delay. Dormancy can be released by 1 year after-ripening treatment. Using a cDNA-amplified fragment length polymorphism (cDNA-AFLP) approach we compared the gene expression patterns of dormant and after-ripened seeds, air-dry or during one day imbibition and analyzed 15,000 cDNA fragments. Among them 1020 were found to be differentially regulated by dormancy. Of 412 sequenced cDNA fragments, 83 were assigned to a known function by search similarities to public databases. The functional categories of the identified dormancy maintenance and breaking responsive genes, give evidence that after-ripening turns in the air-dry seed to a new developmental program that modulates, at the RNA level, components of translational control, signaling networks, transcriptional control and regulated proteolysis.

Blotting, Northern↗
PubMed1996

A molecular study of dormancy breaking and germination in seeds of Trollius ledebouri.

A cDNA library was generated from seeds of Trollius ledebouri cv. Golden Queen after GA3 treatment. Five clones encoded mRNAs which were down-regulated during dormancy breaking and the initial stages of germination. Two of these showed homology to storage proteins (pPCB3 and pPCB4) and one each to the late-embryogenesis-abundant (LEA) group 2 dehydrin proteins (pPCB2), a barely glucose dehydrogenase (pPCB6) and the glutathione S-transferase (GST) superfamily (pPCB7). Transcript levels declined over 8 days in GA3-treated seeds. In dormant imbibed seeds transcript levels were relatively unchanged over the same period except for the PCB3 transcript, the level of which increased.

Amino Acid Sequence↗
PubMed2005

Ethanol breaks dormancy of the potato tuber apical bud.

Growing potato tubers or freshly harvested mature tubers have a dormant apical bud. Normally, this dormancy is spontaneously broken after a period of maturation of the tuber, resulting in the growth of a new sprout. Here it is shown that in in vitro-cultured growing and maturing tubers, ethanol can rapidly break this dormancy and re-induce growth of the apical bud. The in vivo promoter activity of selected genes during this secondary growth of the apical bud was monitored, using luciferase as a reporter. In response to ethanol, the expression of carbohydrate-storage, protein-storage, and cell division-related genes are rapidly down-regulated in tuber tissue. It was shown that dormancy was broken by primary but not by secondary alcohols, and the effect of ethanol on sprouting and gene expression in tuber tissue was blocked by an inhibitor of alcohol dehydrogenase. By contrast, products derived from alcohol dehydrogenase activity (acetaldehyde and acetic acid) did not induce sprouting, nor did they affect luciferase reporter gene activity in the tuber tissue. Application of an inhibitor of gibberellin biosynthesis had no effect on ethanol-induced sprouting. It is suggested that ethanol-induced sprouting may be related to an alcohol dehydrogenase-mediated increase in the catabolic redox charge [NADH/(NADH+NAD+)].

Acetaldehyde↗
PubMed2000

The transduction of the signal for grape bud dormancy breaking induced by hydrogen cyanamide may involve the SNF-like protein kinase GDBRPK.

Alterations in gene expression during early stages of dormancy release in grapevine buds were analyzed to facilitate the identification of gene products that may mediate the signal transduction of a dormancy-release signal, or derepression of meristematic activity. In the present report we describe the identification of GDBRPK, a transcript for an SNF-like protein kinase that is up-regulated upon chemical induction of dormancy release by hydrogen cyanamide (HC). Since SNF and SNF-like protein kinases are known as sensors of stress signals, we hypothesize that GDBRPK may be involved in the perception of a stress signal induced by HC. We also describe a simultaneous and remarkable induction of both PDC and ADH transcripts that was observed shortly after HC application, and was of a transient nature. These data may imply that HC application leads to a transient respiratory stress, which likely results in a temporary increase in the AMP/ATP ratio. Since AMP is known as a stress signal that is sensed by SNF-like kinases, we suggest that the SNF-like GDBRPK could serve as the sensor of this signal.

Alcohol Dehydrogenase↗
PubMed2002

Breaking dormancy is spores of the arbuscular mycorrhizal fungus Glomus intraradices: a critical cold-storage period.

To elucidate the effect of cold storage on spore dormancy in the arbuscular mycorrhizal (AM) fungus Glomus intraradices, spores were cold stratified at 4 degrees C, for either 0, 3, 7, 14, 90 or 120 days, prior to germination tests at 25 degrees C. The results showed that cold stratification longer than 14 days significantly increased spore germination. Moreover, the longer cold storage periods clearly reduced spore mortality from 90% to 50% and considerably altered the hyphal growth pattern. Long polarized hyphae were only observed after cold stratification periods longer than 14 days, involving consequences for root infectivity. The results clearly show that environmental factors, e.g., coldness, can affect the physiology of AM fungal spores.

Cold Temperature↗
PubMed1999

Anatomy of two mechanisms of breaking physical dormancy by experimental treatments in seeds of two North American Rhus species (Anacardiaceae).

Anatomy of the endocarp was studied in relation to the physical dormancy-breaking mechanisms in experimentally treated Rhus aromatica var. aromatica and R. glabra germination units, which include seed plus endocarp (hereafter seeds). The endocarp has three distinct layers, with brachysclereids on the outside, osteosclereids in the middle, and macrosclereids on the inside. Brachysclereids in the carpellary micropyle region (i.e., region immediately adjacent to the integumentary micropyle) are shorter than those in other parts of the endocarp, and the macrosclereids in this region are not elongated. Thus, a weak point is formed in the endocarp. Concentrated sulfuric acid broke seed dormancy in R. aromatica by eroding the brachysclereids and osteosclereids in the carpellary micropyle region, whereas boiling water broke dormancy in seeds of R. glabra by inducing a blister adjacent to the carpellary micropyle.

Journal Article↗
PubMed2000

Morphophysiological dormancy in seeds of two North American and one Eurasian species of Sambucus (Caprifoliaceae) with underdeveloped spatulate embryos.

In contrast to previous reports, the endocarps ("seed coats") of Sambucus species are not impermeable to water; thus, the seeds do not have physical dormancy. Seeds of the North American species Sambucus canadensis and S. pubens and of the European species S. racemosa have spatulate shaped embryos that are ∼60% fully developed (elongated) at seed maturity. The embryo has to extend to the full length of the seed to germinate. Embryos in freshly matured seeds of S. canadensis and in those of S. pubens grew better at 25°/15°C than at 5°C, whereas the rate of embryo growth in S. racemosa was higher at 5°C than at 25°/15°C. Seeds of all three species germinated to significantly higher percentages in light (14-h photoperiod) than in darkness. Fresh seeds of neither species germinated during 2 wk of incubation over a range of thermoperiods. Warm followed by cold stratification broke dormancy in seeds of S. canadensis and in those of S. pubens. Thus, seeds of these two North American species have deep simple morphophysiological dormancy (MPD). In comparison, seeds of the European species S. racemosa required a cold stratification period only for dormancy break, and thus they have intermediate complex MPD. GA(3) was much more effective in breaking dormancy in seeds of S. racemosa than it was in those of S. canadensis or S. pubens.

Journal Article↗
PubMed2004

[Relationship between breaking of dormancy and reactive oxygen species metabolism in flower buds of pear].

The metabolism of reactive oxygen species in pear (Pyrus bretschneideri Rehd.) flower buds changes greatly during their natural dormancy in winter. The O(-.)(2) production rate increases rapidly during the period of dormancy, but decreases when dormancy finishes (Fig. 5). H(2)O(2) content goes up significantly at the early stage of dormancy, but afterwards falls gradually (Fig. 5). However, ascorbic acid (AsA) and reduced glutathione (GSH) contents show a different changing trend: descending at first and keeping at relatively low levels during the process of dormancy, but rising during breaking of dormancy (Fig. 4). The activities of superoxide dismutase (SOD), ascorbic peroxidase (APX) and glutathione reductase (GR) descend during the process of dormancy, but rise during breaking of dormancy, although at different rates for different enzymes (Figs. 1, 3). On the contrary, the activity of catalase (CAT) increases sharply at the beginning of dormancy, keeps at a stable high level during dormancy, and gradually decreases at the end of dormancy period (Fig. 2). The activity of peroxidase (POD) even keeps increasing during dormancy and breaking of dormancy (Fig. 1). The results show that the metabolism of reactive oxygen species has certain strong correlation with the natural dormancy of pear flower buds in winter.

Ascorbic Acid↗
PubMed1983

Reversibility characteristics of glucose-induced trehalase activation associated with the breaking of dormancy in yeast ascospores.

The breaking of dormancy in yeast ascospores by addition of glucose is associated with a sudden tenfold increase in the activity of trehalase. The rapid activation of trehalase is followed by a slower inactivation process which is greatly retarded in the presence of nitrogen sources and cycloheximide. When glucose is washed away from the spores after some time and the spores resuspended in glucose-free medium, the trehalase activity decreases sharply. Subsequent addition of new glucose partially reactivates the enzyme. The extent of reactivation decreases further with each subsequent activation/inactivation step. Changing the duration of the inactivation periods has no effect on this diminution of the reversibility. However, prolonging the duration of the activation step speeds up the loss of reversibility. On the other hand, addition of a nitrogen source or cycloheximide completely prevents the loss of reversibility. The results of the reversibility studies are in agreement with the phosphorylation mechanism which has been proposed for the underlying molecular process of trehalase activation. Apparently, they are also in agreement with proteolytic breakdown being responsible for the inactivation of trehalase after its initial activation. However, the effect of cycloheximide and nitrogen sources, at least in ascospores, does not appear to be due to inhibition or repression of protease synthesis, respectively, since the addition in the presence of glucose of a nitrogen source after trehalase inactivation immediately reactivates the enzyme completely.

Ascomycota↗
PubMed1985

Glycerol formation after the breaking of dormancy of Phycomyces blakesleeanus spores. Role of an interconvertible glycerol-3-phosphatase.

The breaking of dormancy of Phycomyces blakesleeanus spores by a heat shock was followed by a transient production of glycerol, which culminated within 5-10 min and was terminated at 20 min. Extracts of spores contained a magnesium-dependent glycerol-3-phosphatase active on both L-glycerol 3-phosphate and dihydroxyacetone phosphate but having more affinity for the first substrate than for the second. In extracts from dormant spores, the phosphatase was profoundly inhibited by physiological concentrations of inorganic phosphate, which induced cooperativity for the substrate, whereas the enzyme from heat-activated spores was much less inhibited and this difference in kinetic properties persisted after gel filtration of the enzymic preparation. When measured at 1 mM phosphate and 0.1 mM glycerol 3-phosphate, the phosphatase activity was undetectable in dormant spores, increased sharply during the heat treatment and the following 5 min at 25 degrees C, then fell again to a low value by 20 min. A similar transient activation of the enzyme was observed following the breaking of dormancy by incubation of the spores in the presence of 0.1 M ammonium acetate. Incubation of a cell-free extract or of the partially purified glycerol-3-phosphatase in the presence of ATP-Mg and the catalytic subunit of cyclic-AMP-dependent protein kinase released the enzyme from inhibition by phosphate and endowed it with the same kinetic properties as did the heat treatment of the spores. It appears therefore most likely that phosphorylation of glycerol-3-phosphatase by cyclic-AMP-dependent protein kinase causes its activation and that this transient process explains the equally transient formation of glycerol by the spores after the heat shock.

Cyclic AMP↗
PubMed2006

DELLA-mediated cotyledon expansion breaks coat-imposed seed dormancy.

Seed dormancy is a key adaptive trait in plants responsible for the soil seed bank. The long established hormone-balance theory describes the antagonistic roles of the dormancy promoting plant hormone abscisic acid (ABA), and the germination promoting hormone gibberellin (GA) in dormancy control. Light, temperature, and other dormancy-breaking signals function to modulate the synthesis and perception of these hormones in the seed. However, the way in which these hormones control dormancy in the imbibed seed remains unknown. Here, we show that the DELLA protein regulators of the GA response are required for dormancy and describe a model through which hormone signal integration and dormancy regulation is achieved. We demonstrate that cotyledon expansion precedes radicle emergence during Arabidopsis seed germination and that a striking correlation exists between final seedling cotyledon size and seed dormancy in the DELLA mutants. Furthermore, twelve previously characterized seed-dormancy mutants are also defective in the control of cotyledon size in a manner consistent with their effect on germination potential. We propose that DELLA-mediated, light-, temperature-, and hormone-responsive cotyledon expansion prior to radicle emergence overcomes dormancy imposed by the seed coat and underlies seed-dormancy control in Arabidopsis.

Abscisic Acid↗
PubMed2002

KNAP2, a class I KN1-like gene is a negative marker of bud growth potential in apple trees (Malus domestica [L.] Borkh.).

The determinism of bud bursting pattern along the 1-year-old shoot was studied at the molecular and morphological levels in the apple tree variety 'Lodi' which shows an acrotonic tendency. At the molecular level, the expression of KNAP2, which belongs to the class I KN1-like gene family, was studied. Measurements were carried out during dormancy (October), breaking dormancy (January) and just before bud bursting (March). The results showed that KNAP2 is more highly expressed in buds that will remain at rest in the spring. Expression of KNAP2 was found in the meristem and in the marginal meristem of the two latest shaped primordia. In the January and March buds, this gene is also expressed in the procambial zone underneath the apical meristem. This study therefore suggests that KNAP2 may be considered as a negative marker of bud growth potential and that the growth inhibition in proximal buds could partially result from differential gene activity. At the morphological level, it was shown that no organogenetic activity took place between October and March as revealed by the constant number of leaf primordia in buds. Nevertheless, those buds likely to grow the following spring had a larger size and fewer hard scales than other buds. This suggests that genetic control may act together with other mechanisms, possibly physical (number of scales) or biochemical, to control bud inhibition.

Base Sequence↗
PubMed2006

Ecophysiology of seed dormancy in the Australian endemic species Acanthocarpus preissii (Dasypogonaceae).

BACKGROUND AND AIMS: Seedlings of Acanthocarpus preissii are needed for coastal sand dune restoration in Western Australia. However, seeds of this Western Australian endemic have proven to be very difficult to germinate. The aims of this study were to define a dormancy-breaking protocol, identify time of suitable conditions for dormancy-break in the field and classify the type of seed dormancy in this species. METHODS: Viability, water-uptake (imbibition) and seed and embryo characteristics were assessed for seeds collected in 2003 and in 2004 from two locations. The effects of GA(3), smoke-water, GA(3) + smoke-water and warm stratification were tested on seed dormancy-break. In a field study, soil temperature and the moisture content of soil and buried seeds were monitored for 1 year. KEY RESULTS: Viability of fresh seeds was >90 %, and they had a fully developed, curved-linear embryo. Fresh seeds imbibed water readily, with mass increasing approx. 52 % in 4 d. Non-treated fresh seeds and those exposed to 1000 ppm GA(3), 1 : 10 (v/v) smoke-water/water or 1000 ppm GA(3) + 1 : 10 (v/v) smoke-water/water germinated <8 %. Fresh seeds germinated to >80 % when warm-stratified for at least 7 weeks at 18/33 degrees C and then moved to 7/18 degrees C, whereas seeds incubated continuously at 7/18 degrees C germinated to <20 %. CONCLUSIONS: Seeds of A. preisii have non-deep physiological dormancy that is released by a period of warm stratification. Autumn (March/April) is the most likely time for warm stratification of seeds of this species in the field. This is the first report of the requirement for warm stratification for dormancy release in seeds of an Australian species.

Adaptation, Physiological↗