Different Stages Of Germination Research Articles

Ability of chestnut oak to tolerate acorn pruning by rodents

Acorns of many white oak species germinate soon after autumn seed fall, a characteristic widely interpreted as a general adaptation to escape predation by small rodents. However, the mechanism by which early, rapid germination allows escape and/or tolerance of seed damage remains unclear. Here we reported how specific germination traits of chestnut oak (Quercus montana) acorns, and those of other white oak species, allow successful escape from acorn pruning by rodents. During germination, chestnut oak acorns develop elongated cotyledonary petioles, which extend beyond the distal end of the acorn (1-2cm) to the point at which the epicotyl and radicle diverge. However, granivorous rodents often prune the taproots above or below the plumule when eating or caching these germinated acorns in autumn. Hence, we hypothesized elongation of cotyledonary petioles allows chestnut oaks to escape acorn pruning by rodents. We simulated pruning by rodents by cutting the taproot at different stages of germination (radicle length) to evaluate the regeneration capacity of four resulting seedling remnants following taproot pruning: acorns with the plumule (remnant I), acorns without the plumule (remnant II), and pruned taproots with (remnant III) or without the plumule (remnant IV). Our results showed that remnant I germinated into seedlings regardless of the length of the taproot previously pruned and removed. Remnant III successfully germinated and survived provided that taproots were ≥6cm in length, whereas remnant IV was unable to produce seedlings. Remnant II only developed adventitious roots near the severed ends of the cotyledonary petioles. Field experiments also showed that pruned taproots with the plumule successfully regenerated into seedlings. We suggest that the elongated cotyledonary petioles, typical of most white oak species in North America, represent a key adaptation that allows frequent escape from rodent damage and predation. The ability of pruned taproots to produce seedlings suggests a far greater resilience of white oaks to seed predation than previously anticipated.

Germination potential index of Sindh rice cultivars on biochemical basis, using amylase as an indicator

Time sequence analysis of germination and vigor of five rice cultivars were carried out by investigating the associated biochemical changes. The experiments were conducted with varying periods of incubation for germination and varietal differences were observed for different parameters. Alpha amylase activities were found to be directly correlated with germination percentage. Gradual increase in reducing sugars along with α-amylase activity was observed, while total carbohydrates decreased as germination proceeded. The genetic variability of seed vigor of rice cultivars may be attributed to varietal differences of α-amylase activity at different stages of germination. Simultaneous increase in reducing sugars due to degradation of reserve carbohydrates was observed. The results indicated that α-amylase activity is a biochemical indicator showing different germination abilities of rice varieties, leading to different seed vigor. Among all five seed cultivars, SADA HAYAT demonstrated maximum seed vigor and alpha amylase activity along with germination period. This cultivar shows a potential for maximum production for successful breeding program.

Changes in protein composition and protein phosphorylation during somatic embryogenesis and plant regeneration in peanut (Arachis hypogaea L.)

Changes in protein profiles and protein phosphorylation were studied in various stages of germinating somatic and zygotic embryos. Many proteins, which were expressed in cotyledonary stage somatic embryos, were also present in the zygotic embryos obtained from mature dry seed. The intensity of 22 kDa protein was much higher in zygotic embryos in comparison to cotyledonary somatic embryos. Proteins of 55, 53, 27 and 25 kDa did not vary in expression during different stages of germination of somatic and zygotic embryos. There was rapid accumulation of 28 kda protein in germinating zygotic and somatic embryos at 3 rd stage and persisted during the subsequent stages of germination indicating the emergence of radical and plumule. A clear difference was observed in the patterns of protein phosphorylation in germinating somatic and zygotic embryos. A 50 kDa protein was heavily phosphorylated in mature zygotic embryos at 2 nd stage of germination and disappeared in 3 rd stage of germination. Protiens of 50 and 43 kDa proteins showed enhanced phosphorylation up to 3 rd stage and drastic reduction was observed at 4 th stage. In addition, phosphorylation of 68 and 65 kDa specifically appeared in 3 rd stage of germinating somatic embryos and were not observed during any germinating stages of zygotic embryos.

보리의 제맥과정 중 Arabinoxylan의 용해성 변화

Barleys at different malting stages from steeping to 5 day germination were investigated for soluble, insoluble, and total arabinoxylans at three different extraction temperatures of 21, 45 and 65℃. Slight differences in total arabinoxylan levels in barleys were observed during malting stages. During germination, initially insoluble arabinoxylan could be more soluble, thus the solubilized arabinoxylan tended to increase until 4 day germination. The proportion of soluble arabinoxylan in germinating barleys was increased from ambient temp (21℃) to 45 or 65℃. Two barley malt samples were selected at two different stages of germination, well-modified malt germinated for 96 hr and poorly-modified malt for 60 hr, and mashed isothermally at 45, 55, 65, or 75℃ for 2 hr. Increasing temperature over 45 to 75℃ slightly decreased the amount of arabinoxylan solubilized in wort. Arabinoxylan content of wort from well-modified malt was not significantly different from poorly-modified malt at all mashing temperatures.

Oxygreen Process Applied on Nongerminated and Germinated Wheat: Role of Hydroxamic Acids

Wheat samples were taken at different stages of germination characterized by their falling number (which is a relevant indicator of germination) from 400 to 60 s. Each batch was treated by the Oxygreen process, a treatment by ozone, in a closed sequential batch reactor. Leucotriene B4 (LTB 4) was induced by germination, but ozone treatment did not increase this effect. Extract obtained from these wheat batches was applied on human epithelial bronchial cells. Wheat extract from nongerminated wheat did not induce any DNA adduct. More the wheat germination gets underway, more DNA adducts are observed. In contrast, germination did not affect the cell viability. Ozonization of wheat exemplified genotoxic effects only if the wheat was germinated. The implication of hydroxamic acids is discussed. In conclusion, ozonization of wheat, of high milling quality, does not pose any problem.

Sequence, expression and tissue localization of a gene encoding a makorin RING zinc-finger protein in germinating rice ( Oryza sativa L. ssp . Japonica) seeds

The makorin ( MKRN) RING finger protein gene family encodes proteins (makorins) with a characteristic array of zinc-finger motifs and which are present in a wide array of eukaryotes. In the present study, we analyzed the structure and expression of a putative makorin RING finger protein gene in rice ( Oryza sativa L. ssp . Japonica cv. Nipponbare). From the analysis of the genomic ( AP003543), mRNA ( AK120250) and deduced protein ( BAD61603) sequences of the putative MKRN gene of rice, obtained from GenBank, we found that it was indeed a bona fide member of the MKRN gene family. The rice MKRN cDNA encoded a protein with four C3H zinc-finger-motifs, one putative Cys-His zinc-finger motif, and one RING zinc-finger motif. The presence of this distinct motif organization and overall amino acid identity clearly indicate that this gene is indeed a true MKRN ortholog. We isolated RNA from embryonic axes of rice seeds at various stages of imbibition and germination and studied the temporal expression profile of MKRN by RT–PCR. This analysis revealed that MKRN transcripts were present at all the time points studied. It was at very low levels in dry seeds, increased slowly during imbibition and germination, and slightly declined in the seedling growth stage. After 6 days of germination, an organ-dependent expression pattern of MKRN was observed: highest in roots and moderate in leaves. Similarly to MKRN transcripts, transcripts of cytoskeletal actin and tubulin were also detected in dry embryos, steadily increased during imbibition and germination and leveled off after 24 h of germination. We studied the spatial expression profile of MKRN in rice tissues, by using a relatively fast, simple and effective non-radioactive mRNA in situ hybridization (NRISH) technique, which provided the first spatial experimental data that hints at the function of a plant makorin. This analysis revealed that MKRN transcripts were expressed in young plumules, lateral root primordia, leaf primordia, leaves and root tissues at many different stages of germination. The presence of MKRN transcripts in dry seeds, its early induction during germination and its continued spatiotemporal expression during early vegetative growth suggest that MKRN has an important role in germination, leaf and lateral root morphogenesis and overall development in rice.

Changes of Folates, Dietary Fiber, and Proteins in Wheat As Affected by Germination

Wheat kernels of the cultivar 'Tommi' were germinated for up to 168 h at 15, 20, 25, or 30 degrees C. Samples were taken at different stages of germination and were analyzed for the quantitative protein composition using an extraction/HPLC method, for folate vitamers using a stable isotope dilution assay, and for soluble, insoluble, and total dietary fiber using a gravimetric method. Gluten proteins were substantially degraded during germination. During the first stages of germination the degradation of glutenins was predominant, whereas longer germination times were required to degrade gliadins. The optimal temperature for gliadin degradation was 20 degrees C, and that for glutenin degradation was 25 degrees C. Omega5- and omega1,2-gliadins were less sensitive to proteolytic degradation than alpha- and gamma-gliadins, and LMW subunits of glutenin were less sensitive than HMW subunits. During germination a time- and temperature-dependent increase of total folate occurred. A maximum 3.6-fold concentration was obtained after 102 h of germination at 20 and 25 degrees C including 5-methyltetrafolate as the major vitamer. The concentration of dietary fiber remained constant or decreased during the first 96 h of germination. Prolonged germination times of up to 168 h led to a substantial increase of total dietary fiber and to a strong increase of the soluble dietary fiber by a factor of 3, whereas the insoluble fiber decreased by 50%.

Differentiation inside multicelled macroconidia of Fusarium culmorum during early germination

Multicelled conidia are formed by many fungal species, but germination of these spores is scarcely studied. Here, the germination and the effects of antimicrobials on multicompartment macroconidia of Fusarium culmorum were investigated. Germ-tube formation was mostly from apical compartments. The intracellular pH (pH in) of the different individual cells of the macroconidia was monitored during germination. The pH in varied among different compartments and during different stages of germination. The internal pH was lowest in ungerminated cells and rose during germ-tube formation and was highest in new germ tubes. Antifungal compounds affect the pH in and differentiation of the conidia. The pH in inside the macroconidial compartments was lowered very fast in the presence of nystatin (1 and 4 μg/ml). At sublethal doses (0.3 μg/ml), the apical compartments were preferentially targeted showing lower pH in values. The reduced germination capacity of apical compartments under these conditions was compensated by an increased germination capacity of middle compartments.

Lipoxygenase-mediated metabolism of storage lipids in germinating sunflower cotyledons and ?-oxidation of (9Z,11E,13S)-13-hydroxy-octadeca-9,11-dienoic acid by the cotyledonary glyoxysomes

During the early stages of germination, a lipid-body lipoxygenase is expressed in the cotyledons of sunflowers (Helianthus annuus L.). In order to obtain evidence for the in vivo activity of this enzyme during germination, we analyzed the lipoxygenase-dependent metabolism of polyunsaturated fatty acids esterified in the storage lipids. For this purpose, lipid bodies were isolated from etiolated sunflower cotyledons at different stages of germination, and the storage triacylglycerols were analyzed for oxygenated derivatives. During the time course of germination the amount of oxygenated storage lipids was strongly augmented, and we detected triacylglycerols containing one, two or three residues of (9Z,11E,13S)-13-hydro(pero)xy-octadeca-9,11-dienoic acid. Glyoxysomes from etiolated sunflower cotyledons converted (9Z,11E,13S)-13-hydroxy-octadeca-9,11-dienoic acid to (9Z,11E)-13-oxo-octadeca-9,11-dienoic acid via an NADH-dependent dehydrogenase reaction. Both oxygenated fatty acid derivatives were activated to the corresponding CoA esters and subsequently metabolized to compounds of shorter chain length. Cofactor requirement and formation of acetyl-CoA indicate degradation via beta-oxidation. However, beta-oxidation only proceeded for two consecutive cycles, leading to accumulation of a medium-chain metabolite carrying an oxo group at C-9, equivalent to C-13 of the parent (9Z,11E,13S)-13-hydroxy-octadeca-9,11-dienoic acid. Short-chain beta-oxidation intermediates were not detected during incubation. Similar results were obtained when 13-hydroxy octadecanoic acid was used as beta-oxidation substrate. On the other hand, the degradation of (9Z,11E)-octadeca-9,11-dienoic acid was accompanied by the appearance of short-chain beta-oxidation intermediates in the reaction mixture. The results suggest that the hydroxyl/oxo group at C-13 of lipoxygenase-derived fatty acids forms a barrier to continuous beta-oxidation by glyoxysomes.

Vivipary in the Cactaceae: Its taxonomic occurrence and biological significance

Summary Vivipary, a rare reproductive strategy in flowering plants, has been previously reported in only four species of the Cactaceae. In this paper, eight additional examples ( Cleistocactus smaragdiflorus , Disocactus martianus , the hybrid Epiphyllum X Fern la Borde , Harrisia martinii , Lepismium ianthothele , L. monacanthum , Rhipsalis micrantha forma micrantha , and R. baccifera subsp. horrida ) of vivipary in cultivated cacti from tribes Hylocereeae, Rhipsalideae, and Trichocereeae are documented. The plants had fully-developed and mature fruits containing seeds at different stages of germination, including tiny embryos emerging from the seed coat to young, healthy seedlings with well-developed organs, such as cotyledons and radicles. Several features, though not unique, distinguish cactus fruits with viviparous seedlings. Foremost, the fruits are fleshy with abundant mucilage and a relatively thick, often transparent pericarp. The seeds are generally numerous and embedded in a transparent, white or red pulp. The occurrence of vivipary in taxa from four phylogenetically distinct tribes of the subfamily Cactoideae suggests an independent origin and indicates that this reproductive strategy may be more widespread in the family than originally thought. Vivipary in the Cactaceae is regarded as a form of cryptovivipary, a condition in which the zygote develops inside the fruit without penetrating the ovary wall for dispersal purposes, which in turn is considered a subcategory of true vivipary. Further, vivipary is interpreted as an adaptive reproductive strategy that enables seedlings to establish more rapidly.

Differential gene expression during seed germination in barley (Hordeum vulgare L.).

A barley cDNA macroarray comprising 1,440 unique genes was used to analyze the spatial and temporal patterns of gene expression in embryo, scutellum and endosperm tissue during different stages of germination. Among the set of expressed genes, 69 displayed the highest mRNA level in endosperm tissue, 58 were up-regulated in both embryo and scutellum, 11 were specifically expressed in the embryo and 16 in scutellum tissue. Based on Blast X analyses, 70% of the differentially expressed genes could be assigned a putative function. One set of genes, expressed in both embryo and scutellum tissue, included functions in cell division, protein translation, nucleotide metabolism, carbohydrate metabolism and some transporters. The other set of genes expressed in endosperm encodes several metabolic pathways including carbohydrate and amino acid metabolism as well as protease inhibitors and storage proteins. As shown for a storage protein and a trypsin inhibitor, the endosperm of the germinating barley grain contains a considerable amount of residual mRNA which was produced during seed development and which is degraded during early stages of germination. Based on similar expression patterns in the endosperm tissue, we identified 29 genes which may undergo the same degradation process.

Structural Elucidation of Oxygenated Storage Lipids in Cucumber Cotyledons: IMPLICATION OF LIPID BODY LIPOXYGENASE IN LIPID MOBILIZATION DURING GERMINATION

At early stages of germination, a special lipoxygenase is expressed in cotyledons of cucumber and several other plants. This enzyme is localized at the lipid storage organelles and oxygenates their storage triacylglycerols. We have isolated this lipid body lipoxygenase from cucumber seedlings and found that it is capable of oxygenating in vitro di- and trilinolein to the corresponding mono-, di-, and trihydroperoxy derivatives. To investigate the in vivo activity of this enzyme during germination, lipid bodies were isolated from cucumber seedlings at different stages of germination, and the triacylglycerols were analyzed for oxygenated derivatives by a combination of high pressure liquid chromatography, gas chromatography/mass spectrometry, and nuclear magnetic resonance spectroscopy. We identified as major oxygenation products triacylglycerols that contained one, two, or three 13S-hydroperoxy-9(Z),11(E)-octadecadienoic acid residues. During germination, the amount of oxygenated lipids increased strongly, reaching a maximum after 72 h and declining afterward. The highly specific pattern of hydroperoxy lipids formed suggested the involvement of the lipid body lipoxygenase in their biosynthesis. These data suggest that this lipoxygenase may play an important role during the germination process of cucumber and other plants and support our previous hypothesis that the specific oxygenation of the storage lipids may initiate their mobilization as a carbon and energy source for the growing seedling.

Changes in chromatin structure associated with germination of maize and their relation with desiccation tolerance

ABSTRACTMorphological and physicochemical measurements of chromatin condensation were made on germinating maize (Zea mays L.) radicles to determine whether the loss of genetic activities that occurs during the loss of desiccation tolerance is linked to irreversible changes in chromatin condensation. Chromatin samples were compared at different stages of germination (0, 24 and 72 h after imbibition), before (control) and after 24 h of desiccation. Morphological changes in chromatin structure and condensation were characterized by a qualitative and quantitative electron microscope study of chromatin which was allowed to spread in 0.2 mol m−3 EDTA and then laid on coated microscope grids. The experiments showed similar levels of chromatin condensation in quiescent embryos and 24‐h‐old radicles (desiccation‐tolerant material). After 72 h of imbibition, when radicle emergence and desiccation intolerance had ceased, the chromatin underwent a major decondensation towards various lower order folded structures. Regardless of the desiccation tolerance stage, an in vivo drying treatment of 24‐ and 72‐h‐old radicles before chromatin extraction did not induce significant changes in the extent of condensation compared to their respective controls. Similar conclusions were drawn from measurements of several spectroscopy properties (absorbance ratios: A260/A240, A260/A400; thermal denaturation, and linear electric dichroism) of chromatin fragments that were obtained after nuclease digestion and then dissolved in 0‐2 mol m−3 EDTA. In quiescent and 24‐h‐old material, chromatin fragments were poorly soluble but highly stable during thermal denaturation. Chromatin fragments were 3‐5‐fold more soluble and less thermally stable in 72‐h‐old material than in 24‐h‐old material. In vivo desiccation had no significant effects on these properties compared to the respective controls. Collectively these data suggest that desiccation did not induce irreversible changes in the condensation properties of chromatin. The likelihood that the decondensation process occurring during germination is linked to the loss of desiccation tolerance is discussed.

The Involvement of Respiration in Free Radical Processes during Loss of Desiccation Tolerance in Germinating Zea mays L. (An Electron Paramagnetic Resonance Study).

When germinating Zea mays L. seeds are rapidly desiccated, free radical-mediated lipid peroxidation and phospholipid de-esterification is accompanied by a desiccation-induced buildup of a stable free radical associated with rapid loss of desiccation tolerance. Comparison of the electron paramagnetic resonance and electron nuclear double resonance properties of this radical with those of the radical in dried, desiccation-intolerant moss showed that the two were identical. At the subcellular level, the radical was associated with the hydrophilic fraction resulting from lipid extraction. Isolated mitochondria subjected to drying were also found to accumulate an identical radical in vitro. When increasing concentrations of cyanide were used, a significant positive correlation was shown between rates of respiration and the accumulation of the radical in desiccation-intolerant tissues. Another positive correlation was found when rates of O2 uptake by radicles at different stages of germination were plotted against free radical content following desiccation. This indicates that free radical production is closely linked to respiration in a process likely to involve the desiccation-induced impairment of the mitochondrial electron transport chain to form thermodynamically favorable conditions to induce accumulation of a stable free radical and peroxidized lipids. Modulation of respiration using a range of inhibitors resulted in broadly similar modulation of the buildup of the stable free radical. One site of radical generation was likely to be the NADH dehydrogenase of complex I and probably as a direct consequence of desiccation-impaired electron flow at or close to the ubiquinone pool.

Transient occurrence of lipoxygenase and glycoprotein gp49 in lipid bodies during fat mobilization in anise seedlings

The patterns of lipid-body proteins prepared at different stages of germination from seedlings of anise (Pimpinella ansium L.) were investigated. During the stage of fat mobilization, a set of proteins is synthesized de novo and transferred to existing lipid bodies. Analysis of the protein constituents, detected either by protein staining, concanavalin-A/peroxidase staining or immunoreaction on Western blots showed three distinct protein species: a lipoxygenase firmly integrated into the lipid bodies, a glycoprotein gp50 only extractable from the lipid bodies by treatment with sodium dodecyl sulfate and a glycoprotein gp49 solubilized by diethyl-ether treatment of lipid bodies. Both the lipoxygenase immunodetected on Western blots and gp49 stained with concanavalin-A/ peroxidase conjugate occurred transiently in the lipidbody fraction, reaching maximum concentrations between days 6 and 13 of germination. This behavior was in contrast to the decreasing level of the 18.4-kDa oleosin already present at the beginning of germination.

Distribution of diamine oxidase activity and polyamine pattern in bean and soybean seedlings at different stages of germination

Diamine oxidase (DAO, EC 1.4.3.6.) activity and polyamine content were measured in the shoot apex, leaves, epicotyl, cotyledons, hypocotyl and roots of light‐grown bean (Phaseolus vulgaris L. cv. Lingot) and soybean (Glycine max L. cv. Sakai) seedlings at 3 different stages of germination (5, 8 and 14 days) as well as in embryos and cotyledons from soaked seeds. No DAO activity was detected in embryos and cotyledons of either plants. In bean seedlings DAO activity was only detectable in the shoot apex, primary leaves and cotyledons, while in soybean the activity was only detectable in the hypocotyl and roots. During seedling growth, in both plants, a different pattern of DAO activity was observed. In both species spermidine and spermine were the most abundant polyamines in embryos and cotyledons. Cadaverine, absent in bean, was only detected in soybean embryos. In the seedlings of both plants, increasing gradients of putrescine, spermidine and spermine from base to shoot apex were found. A high concentration of cadaverine was present in soybean hypocotyls and roots. A possible correlation between DAO activity and the endogenous content of the preferential substrate is discussed in relation to the possible involvement of the enzyme in regulating the cellular level of polyamines.

Distribution of diamine oxidase activity and polyamine pattern in bean and soybean seedlings at different stages of germination

Distribution of diamine oxidase activity and polyamine pattern in bean and soybean seedlings at different stages of germination

Sequential expression and differential hormonal regulation of proteolytic activities during germination in Zea mays L.

We have characterized the proteolytic activities (proteases in cooperation with carboxypeptidases) involved in the different stages of germination of maize (Zea mays L.) grains. A sequential expression of different groups of proteases (aspartic, cysteine, serine and metallo-proteases) with pH optima in the acidic range has been found by using specific protease inhibitors. Pepstatin-sensitive proteolytic activity (aspartic-protease activity) is dominant in resting grains. Germination is accompanied by the appearance of a proteolytic activity which can be enhanced by low-molecular-weight thiol compounds and inhibited by thiol-protease inhibitors, which is indicative of the involvement of cysteine protease(s). This burst of cysteine-protease activity is coincident with the disappearance of the main storage-protein fractions. We conclude from this that cysteine protease(s), with an acid pH optimum, are good candidate(s) for the proteolytic attack of stored protein reserves in maize. After this stage, where cysteine-protease activity is dominant, a period with larger total proteolytic activity starts, coincidentally with the expression of the different types of other proteolytic activities (serine, aspartic and metallo proteases), in addition to the cysteine-protease activity above mentioned. When the development of carboxypeptidase activity during germination was analyzed, the highest activities were found during the earlier and later stages. This result is indicative of a cooperative interaction between carboxypeptidase and endoproteolytic systems in order to obtain a more effective mobilization of storage proteins in germinating maize grains. The phytohormones, gibberellic acid (GA3) and abscisic acid (ABA) which can stimulate or inhibit, respectively, the total proteolytic activity in extracts from germinating grains, exert a differential effect on the different proteolytic activities here detected.

Stereological analysis of cotyledon tissue inVicia faba L. var. aquadulce during germination

Stereological analysis was carried out on cotyledon tissue at three different stages of germination. The tissue was selected by reference to adjacent sections which were assayed histochemically for protease activity. Day six tissue had no activity while eight and 14-day tissue did. Results show that during germination both tissue and cellular components undergo changes. The cells increase in size, the intercellular spaces increase, the cytoplasm increases in volume, the protein bodies swell and fuse, and small starch grains appear while the large starch grains do not undergo any major changes.

Effects of ethylene and some other environmental factors on different stages of germination in red root pigweed (Amaranthus retroflexusL.) seeds*

Abstract.Ethylene was found to promote two distinct processes during germination of redroot pigweed (Amarantus retroflexusL.) seeds: embryo expansion that splits the seed coat (incomplete germination), and radicle penetration through the more elastic endosperm (complete germination). The two events can be separated in time by subjecting seeds to low water potential or low CO2levels, which arrest germination of some seeds at the incomplete stage. Ethylene applications to incompletely germinated seeds promote complete germination, with a response threshold near 0.02 cm3m−3and saturation near 0.5 cm3m−3. Higher ethylene concentrations (0.5 to 50 cm3m−3) given during the first day of seed imbibition also increase the percentage of seeds which initiate embryo expansion and split the seed coat. Light and elevated CO2also promote radicle penetration of the endosperm in seeds incubated under water stress. The results support the view that the germination pause at the incomplete stage is an adaptation to environmental stresses that can be overcome with exogenous ethylene or certain other stimuli.