Physiological changes following the breaking of dormancy of Saccharomyces cerevisiae ascospores.
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Results for “dormancy breaking”
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[Effect of storage methods on breaking seed dormancy of Trollius chinensis Bge].
OBJECTIVE: Exploring the best seed storage method for Trollius chinensis. METHOD: Different temperatures were applied to the seed storage in wet sand and dry sand, and the embryo-endosperm ratio and germination rate were inspected. RESULT: The dormancy of T. chinensis seeds could only be broken in lower temperatures. The newly collected seeds set out to germinate after 75 days of storage at 5-6 degrees C when the embryo-endosperm ratio reached 47%, and the time of seed germination varied with the length of storage time before low-temperature treatment. CONCLUSION: The best storage method for the seed of T. chinensis is keeping it in dry for 6-8 months with an additional 1 month of low-temperature treatment to follow.
Drug Storage↗
Polyribosome formation and RNA synthesis after breaking the dormancy of sugar beet root.
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Plants, Edible↗
Isolation of the GA-response mutant sly1 as a suppressor of ABI1-1 in Arabidopsis thaliana.
Seed dormancy and germination in higher plants are partially controlled by the plant hormones abscisic acid (ABA) and gibberellic acid (GA). ABA establishes dormancy during embryo maturation, whereas GA breaks dormancy and induces germination. Previous attempts to identify GA response genes were confounded because GA mutants are not expected to germinate and, unlike GA auxotrophs, should fail to be rescued by exogenous GA. Here, we describe a screen for suppressors of the ABA-insensitive mutant ABI1-1 that enriches for GA auxotrophs and GA-insensitive mutants. The vast majority (76%) of the suppressors of ABI1-1 strongly resemble GA auxotrophs in that they are severely dwarfed and have dark green foliage and flowers with underdeveloped petals and stamen. Three isolates were alleles of the GA auxotroph ga1. The remaining severe dwarves were not rescued by GA and belong to a single complementation group that we designate sly1 (Sleepy 1). The alleles of sly1 identified are the first recessive GA-insensitive mutations to reflect the full spectrum of GA-associated phenotypes, including the failure to germinate in the absence of the ABI1-1 lesion. Thus, we postulate that SLY1 is a key factor in GA reception.
Abscisic Acid↗
Anaerobic conditions improve germination of a gibberellic acid deficient rice.
Dwarf plants are useful in research because multiple plants can be grown in a small area. Rice (Oryza sativa L.) is especially important since its relatively simple genome has recently been sequenced. We are characterizing a gibberellic acid (GA) mutant of rice (japonica cv 'Shiokari,' line N-71) that is extremely dwarf (20 cm tall). Unfortunately, this GA mutation is associated with poor germination (70%) under aerobic conditions. Neither exogenous GA nor a dormancy-breaking heat treatment improved germination. However, 95% germination was achieved by germinating the seeds anaerobically, either in a pure N2 environment or submerged in unstirred tap water. The anaerobic conditions appear to break a mild post-harvest dormancy in this rice cultivar.
Anaerobiosis↗
Ethylene as a Component of the Emanations From Germinating Peanut Seeds and Its Effect on Dormant Virginia-type Seeds.
The embryonic axes of Spanish-type peanut seeds that do not exhibit dormancy to any extent were found to produce ethylene during germination. Virginia-type peanut seeds of the extremely dormant variety NC-13 produced low levels of ethylene when imbibed but not germinating. Treatments that released dormancy of NC-13 peanut seeds resulted in increased ethylene production by the embryonic axis. The estimated internal concentration of ethylene in Virginia-type peanut seeds was 0.4 ppm at 24 hr of germination. Fumigation with an external concentration of 3.0 to 3.5 ppm for 6 hr was sufficient to break dormancy of Virginia-type peanut seeds. These results suggest that ethylene is associated with the germination processes of non-dormant seeds and participates in the breaking of seed dormancy of dormant peanut varieties.
Journal Article↗
Sodium nitroprusside, cyanide, nitrite, and nitrate break Arabidopsis seed dormancy in a nitric oxide-dependent manner.
The seeds of many plant species are dormant at maturity and dormancy loss is a prerequisite for germination. Numerous environmental and chemical treatments are known to lessen or remove seed dormancy, but the biochemical changes that occur during this change of state are poorly understood. Several lines of research have implicated nitric oxide (NO) as a participant in this process. Here, we show that dormant seeds of Arabidopsis thaliana (L.) Heynh. will germinate following treatment with the NO donor sodium nitroprusside (SNP), cyanide (CN), nitrite or nitrate. In all cases, the NO scavenger c-PTIO effectively promotes the maintenance of seed dormancy. c-PTIO does not, however, inhibit germination of fully after-ripened seeds, and c-PTIO does not interact directly with nitrite, nitrate or CN. We also show that volatile CN effectively breaks dormancy of Arabidopsis seeds, and that CN is the volatile compound in SNP that promotes dormancy loss. Our data support the hypothesis that NO is a signaling molecule that plays an important role in the loss of seed dormancy.
Arabidopsis↗
Changes in endogenous abscisic acid levels during dormancy release and maintenance of mature seeds: studies with the Cape Verde Islands ecotype, the dormant model of Arabidopsis thaliana.
Mature seeds of the Cape Verde Islands (Cvi) ecotype of Arabidopsis thaliana (L.) Heynh. show a very marked dormancy. Dormant (D) seeds completely fail to germinate in conditions that are favourable for germination whereas non-dormant (ND) seeds germinate easily. Cvi seed dormancy is alleviated by after-ripening, stratification, and also by nitrate or fluridone treatment. Addition of gibberellins to D seeds does not suppress dormancy efficiently, suggesting that gibberellins are not directly involved in the breaking of dormancy. Dormancy expression of Cvi seeds is strongly dependent on temperature: D seeds do not germinate at warm temperatures (20-27 degrees C) but do so easily at a low temperature (13 degrees C) or when a fluridone treatment is given to D seeds sown at high temperature. To investigate the role of abscisic acid (ABA) in dormancy release and maintenance, we measured the ABA content in both ND and D seeds imbibed using various dormancy-breaking conditions. It was found that dry D seeds contained higher amounts of ABA than dry ND after-ripened seeds. During early imbibition in standard conditions, there was a decrease in ABA content in both seeds, the rate of which was slower in D seeds. Three days after sowing, the ABA content in D seeds increased specifically and then remained at a high level. When imbibed with fluridone, nitrate or stratified, the ABA content of D seeds decreased and reached a level very near to that of ND seeds. In contrast, gibberellic acid (GA3) treatment caused a transient increase in ABA content. When D seeds were sown at low optimal temperature their ABA content also decreased to the level observed in ND seeds. The present study indicates that Cvi D and ND seeds can be easily distinguished by their ability to synthesize ABA following imbibition. Treatments used here to break dormancy reduced the ABA level in imbibed D seeds to the level observed in ND seeds, with the exception of GA3 treatment, which was active in promoting germination only when ABA synthesis was inhibited.
Abscisic Acid↗
Seed Dormancy in Red Rice : III. Response to Nitrite, Nitrate, and Ammonium Ions.
Sodium nitrite at 10 millimolar breaks dormancy of dehulled red rice (Oryza sativa). While germination is light independent, low pH conditions (pH 3) are required for maximum response. Water and buffer controls at pH 3 remain dormant. The response to nitrite occurs at 25 and 30 degrees C but is reduced at 20 degrees C, although nondormant seeds germinate readily at this temperature. The contact time for response to nitrite is less than 2 h at the start of imbibition. Seeds imbibed first in water show reduced germination when subsequently transferred to nitrite. Dehulled seeds show little or no response to nitrate and ammonium ions.Intact seeds remain dormant in the presence of nitrite or nitrate unless partially dry-afterripened. The pH dependence of nitrite sensitivity is reduced in intact, afterripening seeds. In highly dormant seeds, vacuum infiltration experiments suggest that the hull restricts uptake of nitrite.
Journal Article↗
Seed dormancy and ABA metabolism in Arabidopsis and barley: the role of ABA 8'-hydroxylase.
We have investigated the relationship between seed dormancy and abscisic acid (ABA) metabolism in the monocot barley and the dicot Arabidopsis. Whether dormant (D) or non-dormant (ND), dry seed of Arabidopsis and embryos of dry barley grains all had similarly high levels of ABA. ABA levels decreased rapidly upon imbibition, although they fell further in ND than in D. Gene expression profiles were determined in Arabidopsis for key ABA biosynthetic [the 9-cis epoxycarotenoid dioxygenasegene family] and ABA catabolic [the ABA 8'-hydroxylase gene family (CYP707A)] genes. Of these, only the AtCYP707A2 gene was differentially expressed between D and ND seeds, being expressed to a much higher level in ND seeds. Similarly, a barley CYP707 homologue, (HvABA8'OH-1) was expressed to a much higher level in embryos from ND grains than from D grains. Consistent with this, in situ hybridization studies showed HvABA8'OH-1 mRNA expression was stronger in embryos from ND grains. Surprisingly, the signal was confined in the coleorhiza, suggesting that this tissue plays a key role in dormancy release. Constitutive expression of a CYP707A gene in transgenic Arabidopsis resulted in decreased ABA content in mature dry seeds and a much shorter after-ripening period to overcome dormancy. Conversely, mutating the CYP707A2 gene resulted in seeds that required longer after-ripening to break dormancy. Our results point to a pivotal role for the ABA 8'-hydroxylase gene in controlling dormancy and that the action of this enzyme may be confined to a particular organ as in the coleorhiza of cereals.
Abscisic Acid↗
Gibberellins and the break of bud dormancy in virus-infected stem cuttings of Euphorbia pulcherrima.
Break in bud dormancy in virus-infected stem cuttings of Euphorbia pulcherrima occurs because of the higher quantity of gibberellins present in them than in healthy cuttings in the dormant period of the plant.
Biological Assay↗
Dormancy of Arabidopsis seeds and barley grains can be broken by nitric oxide.
Seeds of Arabidopsis thaliana (L.) Heynh. and grains of barley ( Hordeum vulgare L.) were used to characterize the affects of nitric oxide (NO) on seed dormancy. Seeds of the C24 and Col-1 ecotypes of Arabidopsis are almost completely dormant when freshly harvested, but dormancy was broken by stratification for 3 days at 4 degrees C or by imbibition of seeds with the NO donor sodium nitroprusside (SNP). This effect of SNP on dormancy of Arabidopsis seeds was concentration dependent. SNP concentrations as low as 25 microM reduced dormancy and stimulated germination, but SNP at 250 microM or more impaired seedling development, including root growth, and inhibited germination. Dormancy was also reduced when Arabidopsis seeds were exposed to gases that are generated by solutions of SNP. Nitrate and nitrite, two other oxides of nitrogen, reduced the dormancy of Arabidopsis seeds, but much higher concentrations of these were required compared to SNP. Furthermore, the kinetics of germination were slower for seeds imbibed with either nitrate or nitrite than for seeds imbibed with SNP. Although seeds imbibed with SNP had reduced dormancy, seeds imbibed with SNP and abscisic acid (ABA) remained strongly dormant. This may indicate that the effects of ABA action on germination are downstream of NO action. The NO scavenger 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3 oxide (cPTIO) strengthened dormancy of unstratified and briefly stratified Arabidopsis seeds. Dormancy of three cultivars of barley was also reduced by SNP. Furthermore, dormancy in barley grain was strengthened by imbibition of grain with cPTIO. The data presented here support the conclusion that NO is a potent dormancy breaking agent for seeds and grains. Experiments with the NO scavenger suggest that NO is an endogenous regulator of seed dormancy.
Arabidopsis↗
A postgermination developmental arrest checkpoint is mediated by abscisic acid and requires the ABI5 transcription factor in Arabidopsis.
Seed dormancy is a trait of considerable adaptive significance because it maximizes seedling survival by preventing premature germination under unfavorable conditions. Understanding how seeds break dormancy and initiate growth is also of great agricultural and biotechnological interest. Abscisic acid (ABA) plays primary regulatory roles in the initiation and maintenance of seed dormancy. Here we report that the basic leucine zipper transcription factor ABI5 confers an enhanced response to exogenous ABA during germination, and seedling establishment, as well as subsequent vegetative growth. These responses correlate with total ABI5 levels. We show that ABI5 expression defines a narrow developmental window following germination, during which plants monitor the environmental osmotic status before initiating vegetative growth. ABI5 is necessary to maintain germinated embryos in a quiescent state thereby protecting plants from drought. As expected for a key player in ABA-triggered processes, ABI5 protein accumulation, phosphorylation, stability, and activity are highly regulated by ABA during germination and early seedling growth.
Abscisic Acid↗
Control of seed dormancy in Nicotiana plumbaginifolia: post-imbibition abscisic acid synthesis imposes dormancy maintenance.
The physiological characteristics of seed dormancy in Nicotiana plumbaginifolia Viv. are described. The level of seed dormancy is defined by the delay in seed germination (i.e the time required prior to germination) under favourable environmental conditions. A wild-type line shows a clear primary dormancy, which is suppressed by afterripening, whereas an abscisic acid (ABA)-deficient mutant shows a non-dormant phenotype. We have investigated the role of ABA and gibberellic acid (GA(3)) in the control of dormancy maintenance or breakage during imbibition in suitable conditions. It was found that fluridone, a carotenoid biosynthesis inhibitor, is almost as efficient as GA(3) in breaking dormancy. Dry dormant seeds contained more ABA than dry afterripened seeds and, during early imbibition, there was an accumulation of ABA in dormant seeds, but not in afterripened seeds. In addition, fluridone and exogenous GA(3) inhibited the accumulation of ABA in imbibed dormant seeds. This reveals an important role for ABA synthesis in dormancy maintenance in imbibed seeds.
Abscisic Acid↗
Gibberellin requirement for Arabidopsis seed germination is determined both by testa characteristics and embryonic abscisic acid.
The mechanisms imposing a gibberellin (GA) requirement to promote the germination of dormant and non-dormant Arabidopsis seeds were analyzed using the GA-deficient mutant ga1, several seed coat pigmentation and structure mutants, and the abscisic acid (ABA)-deficient mutant aba1. Testa mutants, which exhibit reduced seed dormancy, were not resistant to GA biosynthesis inhibitors such as tetcyclacis and paclobutrazol, contrarily to what was found before for other non-dormant mutants in Arabidopsis. However, testa mutants were more sensitive to exogenous GAs than the wild-types in the presence of the inhibitors or when transferred to a GA-deficient background. The germination capacity of the ga1-1 mutant could be integrally restored, without the help of exogenous GAs, by removing the envelopes or by transferring the mutation to a tt background (tt4 and ttg1). The double mutants still required light and chilling for dormancy breaking, which may indicate that both agents can have an effect independently of GA biosynthesis. The ABA biosynthesis inhibitor norflurazon was partially efficient in releasing the dormancy of wild-type and mutant seeds. These results suggest that GAs are required to overcome the germination constraints imposed both by the seed coat and ABA-related embryo dormancy.
Abscisic Acid↗
Changes in abscisic acid content and embryo sensitivity to (+)-abscisic acid during the termination of dormancy of yellow cedar seeds.
Yellow cedar seeds are dormant at maturity. The abscisic acid (ABA) content of the embryo (but not the megagametophyte) decreased approximately 2-fold following exposure of seeds to a dormancy-breaking treatment; this process was also accompanied by a 10-fold lowered sensitivity of the embryo to S:-(+)-ABA. A decline in ABA within the seed is not sufficient for dormancy breakage; reduced embryo sensitivity to ABA is also required.
Abscisic Acid↗
Dual action of respiratory inhibitors: inhibition of germination and prevention of dormancy induction in lettuce seeds.
;Grand Rapids' lettuce Lactuca sativa L. seeds germinate readily at 15 degrees C but poorly at 25 degrees C in darkness. When held in dark at 25 degrees C for an extended period, the ungerminated seeds become dormant as shown by their inability to germinate or transfer to 15 degrees C in darkness. Induction of dormancy at 25 degrees C was prevented by exposure to CN(-), azide, salicylhydroxamic acid (SHAM), dinitrophenol, and pure N(2) as determined by subsequent germination at 15 degrees C on removal of inhibitors. The effectiveness of inhibitors to break dormancy declined as dormancy intensified. At relatively low levels, CN(-), SHAM, and azide promoted dark germination at 25 degrees C while at high levels they were inhibitory. Uptake of O(2) by seeds held at 25 degrees C for 4 days in 1.0 millimolar KCN was inhibited by 67% but was promoted 61% when KCN was removed. Correspondingly greater inhibition (79%) and promotion (148%) occurred when 1.0 millimolar SHAM was added to KCN solution. When applied alone, SHAM had little effect on O(2) uptake. These data indicate that Cyt pathway of respiration plays a dominant role in the control of both dormancy induction and germination of lettuce seeds, and ;alternative pathway' is effectively engaged in presence of CN(-). The channeling of respiratory energy use for processes governing germination or dormancy is subject to control by physical and chemical factors.A scheme is proposed that illustrates compensatory use of energy for processes controlling dormancy induction and germination. A block of germination, e.g. by low water potential polyethylene glycol solution or a supraoptimal temperature spares energy to be utilized for dormancy induction while a block of dormancy induction by low levels of CN(-) (similar to GA and light effects) drives germination. Blocking both processes by inhibitors (e.g. CN(-), CN(-) + SHAM) presumably leads to accumulation of ;reducing power' with consequent improvement in O(2) uptake and oxidation rates of processes controlling germination or dormancy induction upon removal of the inhibitors.
Journal Article↗
Mapping QTLs for seed dormancy and the Vp1 homologue on chromosome 3A in wheat.
A major component of the observed genetic variation for pre-harvest sprouting in wheat ( Triticum aestivum L.) appears to be the level of seed dormancy. Group 3 chromosomes have received attention as carrying the R genes for seed-coat color and the taVp1 genes that are orthologous to the maize Vp1 gene which encode a dormancy-related transcription factor. The objectives of the present study were to map quantitative trait loci (QTLs) for seed dormancy on chromosome 3A and to investigate an association between taVp1 or R-A1 and the QTLs detected. A mapping population in the form of recombinant inbred lines developed from the cross between the highly dormant Zenkoujikomugi (Zen) and Chinese Spring (CS) was utilized. Nineteen marker loci, including taVp1, were mapped on chromosome 3A. The taVp1 locus was located in the middle of the long arm, about 85 cM from the centromere. The population was evaluated in duplicate by growing them under controlled environment conditions. Two QTLs for seed dormancy, designated as QPhs.ocs-3A.1 and QPhs.ocs-3A.2, were identified on the short and long arms, respectively. QPhs.ocs-1 explained 23-38% of the phenotypic variation and the Zen allele had a striking effect on maintaining dormancy. QPhs.ocs-2, with a minor effect, was detectable only at the dormancy-breaking stage. Although QPhs.ocs-2 was loosely linked to taVp1 by around 50 cM, they are clearly distinct genes. Zen and CS carry the white R-A1a allele, and no QTL effect was detected in the vicinity region of R-A1. Hence it was concluded that the high dormancy associated with chromosome 3A of Zen is ascribable to QPhs.ocs-1 on the short arm but is not due to the direct contribution of either the taVp1 or R-A1 locus.
Chromosomes, Plant↗