Warm Stratification Research Articles

Germination, seedling growth requirements and antimicrobial properties of Boscia albitrunca — A keystone species in arid southern Africa

Boscia albitrunca (Burch.) Gilg & Gilg-Ben (Capparaceae) is an ecologically, culturally and medicinally important plant in southern Africa. The effect of some abiotic factors on seed germination and seedling growth of B. albitrunca were investigated. Warm stratification (30°C) of intact seeds (with seed coat) for 14days achieved maximum germination (100%). Intact seeds without stratification showed very low germination (8%). Smoke–water (1:500 v/v)-treated seeds (without seed coat) showed a significant increase in germination (83%) compared to the control (47%) at 25°C under a 16h photoperiod. Increasing watering frequency enhanced most of the growth parameters of four-month-old B. albitrunca seedlings. Similar results were obtained when seedlings were treated with 25% Hoagland's nutrient solution. Deficiency of macronutrients (N, P and K) negatively affected growth of B. albitrunca seedlings. Higher antimicrobial activity of the experimental seedlings was observed in 80% ethanol extracts compared to the water extracts. The best minimum inhibitory concentration (MIC) values of 0.39, 0.78 and 0.78mg/ml against Bacillus subtilis, Staphylococcus aureus and Escherichia coli respectively, were observed in 80% ethanol root extracts of seedlings supplied with 25% Hoagland's nutrient solution and grown with phosphorus deficiency. Similar results were obtained for antifungal activity with these treatments. Findings of this study will be useful for the propagation of B. albitrunca plants with insight on ways to promote high antimicrobial activities.

Long-Term Monitoring of a Lagooning Basin Used as Pretreatment Facility for a WTP: Effect on Water Quality and Description of Hydrological and Biological Cycles Using Chemometric Approaches

The drinking water treatment plant (WTP) of the city of Turin (NW Italy), with a treatment capacity of 40 × 106 m3/year, has a basin that is employed as a lagooning pretreatment facility. This study aims to assess the effect of the basin on several environmental parameters (temperature, dissolved oxygen (DO), turbidity, pH, chloride, nitrite, and total chlorophyll) of the river water before entering the WTP and monitor the changes inside the basin caused by the seasonal hydrological and biological cycles. Sampling was carried out on 16 dates over 3 years at the inlet and outlet channel of the basin and in five locations along three depth values (1, 6, and 12 m, i.e., at the bottom). The results of the 3-year monitoring campaign demonstrated that the basin had an effect on pH (p = 6.6 × 10−9), DO (p = 0.000072), turbidity (p = 0.011), and chlorophyll (p = 0.033). No significant changes regarding nitrite (p = 0.11), chloride (p = 0.94), and temperature (p = 0.66) were detected. The results gathered from the sampling campaign inside the basin demonstrated that, during the year, the basin experienced the following: two states of complete mixing in early spring and fall, when the differences in temperature between the surface and the bottom of the basin were less than 1 °C; a condition of late spring/summer stratification with a temperature difference between the surface and the bottom of 4–5 °C and a difference in DO, pH, and total chlorophyll concentration that increased throughout the spring season; and one or more states of summer circulation due to the weak stability of the warm season stratification. During the states of circulation, the persistent algae photosynthetic activity tended to cause a quick change in the concentration of DO, total chlorophyll, and pH value in the most superficial layer of the basin. The results of the principal component analysis (PCA) showed a strong direct relationship between the weight of the first component and the hydrodynamic states of the basin (stratification/circulation) and an inverse relationship between the weight of the second component and the intensity of photosynthetic activity of algae species.

Seed afterripening and germination photoinhibition in the genusCrocus(Iridaceae)

AbstractMediterranean characteristics are attributed to the genusCrocus, which is inadequately studied in terms of seed germination. An afterripening requirement is very common in environments with warm and dry periods, and photoinhibition has been detected in many angiosperms inhabiting dry and open areas. The effects of afterripening and light on seed germination were investigated for the first time in 23 native GreekCrocustaxa, collected from various localities with either a Mediterranean or a temperate climate. Germination experiments were conducted in continuous darkness and in light at the optimal temperature for each taxon, with both freshly collected and afterripened seeds; warm stratification (20°C, darkness) was also examined in 22 taxa. A number of selected taxa were additionally investigated with respect to afterripening outdoors, afterripening and warm stratification at higher temperatures (35 and 25°C, respectively), stratification at 20/10°C, dry storage at low temperatures, response to gibberellic acid and phenology of embryo growth. It was postulated that an afterripening requirement is a characteristic of the genusCrocus, and we found that it can be fulfilled in nature during the Mediterranean dry summer. Also, for the vast majority of the taxa, warm stratification and stratification at 20/10°C can both meet the afterripening requirement. Embryos of the taxa studied are underdeveloped and have to grow prior to germination. Intrageneric differences of seed germination were observed only towards light, with photoinhibition being predominant in taxa from drier environments.

Changes in oxidative patterns during dormancy break by warm and cold stratification in seeds of an edible fruit tree.

The transition from seed dormancy to germination is triggered by environmental factors, and in pomegranate (Punica granatum) seeds higher germination percentages are achieved by warm + cold stratification rather than by cold stratification alone. Our objective was to define the pattern of internal oxidative changes in pomegranate seeds as dormancy was being broken by warm + cold stratification and by cold stratification alone. Embryos isolated from seeds after 1–42 days of warm stratification, after 56 days of warm stratification + 7, 28 or 56 days of cold stratification, and after 1–84 days of cold stratification alone, were used in biochemical tests. Hydrogen peroxide (H2O2), nitric oxide (NO), proline, lipid peroxidation, protein carbonylation, and activities of the scavenging enzymes superoxide dismutase (SOD), hydrogen peroxide enzyme and peroxidase in the embryos were assessed by colorimetric methods. Our results indicated that warm + cold stratification had a stronger dormancy-breaking effect than cold stratification (85% versus 50% germination), which may be attributed to a higher yield of H2O2, NO, lipid peroxidation and protein carbonylation in warm + cold stratification. Furthermore, warm + cold stratification-induced H2O2 change led to greater changes (elevation followed by attenuation) in activities of the scavenging enzymes than that induced by cold stratification alone. These results indicated that restriction of the level of reactive oxygen species change within a positive and safe range by such enzymes promoted seed germination. In addition, a relatively strong elevation of proline during warm + cold stratification also contributed to dormancy breakage and subsequent germination. In conclusion, the strong dormancy alleviating effect of warm + cold stratification on pomegranate seeds may be attributed to the corresponding active oxidative change via H2O2, NO, proline, malondialdehyde, protein carbonylation and scavenging enzymes.

English

This study aimed to investigate the effects of different pre-sowing treatments on Jatropha curcas seed germination rate and seedling early growth. Growth and vigour of the seedlings was assessed through the measurements of growth parameters, in order to identify the best pre-sowing treatment, which guarantees both the highest seed germination rate and the best development and growth of the seedlings. J. curcas seeds of the 'Indian' cultivar were collected in Tamale region (Ghana) and subjected to five different pre-sowing treatments: i) control; ii) soaking in 30°C water for 24 h; iii) hammer shell cracking; iv) warm stratification at 37°C for 24 h; v) hammer shell cracking plus warm stratification at 37°C for 24 h. Amongst the sixteen indices considered in the experiment (six germination indices and ten growth rate indices), results revealed that the tested pre-sowing treatments influenced much more seed germination than seedling growth. Shell cracking treatment enhanced seed germination and warm stratification promoted emergence rate and seedling growth as compared to the other tested treatments. Key words: Physic nut, biodiesel, rural development, vegetable oil, land use.

Germination ecology of the endemic Iberian daffodil Narcissus radinganorum (Amaryllidaceae). Dormancy induction by cold stratification or desiccation in late stages of embryo growth

Aim of study: We studied the germination ecology of a threatened daffodil in order to develop a protocol to produce plants ex-situ from seeds, a key tool for population reinforcement.Area of study: Experiments were carried out both outdoors and in the laboratory in Albacete (Spain).Material and methods: Embryo length, radicle and shoot emergence were analyzed to determine the level of morphophysiological dormancy (MPD). Effects on germination of cold stratification or desiccation in late stages of embryo growth were also studied.Main results: Mean embryo length in fresh seeds was 1.36 mm, needing to grow up to 2.20 mm to be able to germinate. In the laboratory, embryo growth occurred during warm stratification (28/14, 25/10ºC), and then radicle emerged when temperatures went down (15/4ºC in darkness). Phenology study in outdoors conditions revealed that embryo grew during summer-early autumn, short time after seed dispersal in nature (i.e., May); radicle emerged in autumn. The shoot however did not emerge until late winter-early spring, because it was physiologically dormant and required a cold (5ºC) period of 30 days to break dormancy. Early cold temperatures interrupted the embryo growth and induced dormancy in seeds whose embryo had grown 30% with respect to the initial length. Desiccation in seeds whose embryo had grown 30% did not induce dormancy, but did it when the embryo growth reached 70%.Research highlights: Seeds of Narcissus radinganorum have deep simple epicotyl MPD.Key words: dormancy break; radicle emergence; shoot emergence; epicotyl MPD; phenology; secondary dormancy.

Role of Temperature and Gibberellic Acid in Stimulating Embryo Elongation and Radicle Emergence of Hepatica asiatica Nakai Seeds

This research was performed to determine the temperature requirements for embryo growth and radicle emergence of Hepatica asiatica Nakai, a perennial herb native to Korea. Seed viability, embryo growth, and radicle emergence were monitored in seeds exposed to various temperatures (10, 15, <TEX>$20^{\circ}C$</TEX> and <TEX>$30{\rightarrow}15^{\circ}C$</TEX>). Laboratory experiments at various temperatures revealed that (1) embryo elongation occurred effectively between 10 and <TEX>$15^{\circ}C$</TEX>; (2) radicle emergence occurred only at <TEX>$15^{\circ}C$</TEX>; (3) a warm stratification (2-8 weeks at <TEX>$30^{\circ}C$</TEX>) was not required for embryo elongation and radicle emergence, and led to inhibition of radicle emergence; (4) application of gibberellic acid (<TEX>$GA_3$</TEX>) promoted embryo growth, but not radicle emergence. These results suggested that H. asiatica seeds have two separate mechanisms to overcome dormancy, either by <TEX>$GA_3$</TEX> (morphological dormancy) or temperature (physiological dormancy), and warm stratification is not involved in breaking radicle dormancy. These findings indicate that H. asiatica seeds have morphophysiological dormancy.

Pericarp structure of Glebionis coronaria (L.) Cass. ex Spach (Asteraceae) cypselae controls water uptake during germination

AbstractGlebionis coronaria (L.) Cass. ex Spach is a common Mediterranean weed producing distinctive central and peripheral dormant cypselae with a hard fruit coat, which was previously hypothesized to impose physical dormancy. Analysis of water uptake in cypselae and in naked seeds showed that it preferentially takes place at the basal end of the fruit; however, seeds within an intact pericarp do not fully imbibe when compared with naked seeds. Germination was not significantly different between the two heteromorphs, and afterripening or cold stratification did not increase germination, while warm stratification at 35/20°C, as revealed by logistic regression, resulted in a significant improvement. However, loss of viability was also rapid at these high temperatures. Central and peripheral cypselae generally showed very low germination. In both heteromorphs, faster and higher germination (60–70%) was reached only after extensive scarification of pericarp tissue, and full germination was observed only after complete removal of pericarp tissue. Although the pericarp significantly reduced water uptake, no palisade layer(s) of macrosclereids could be observed. Xylem-vessel elements were found running through the basal end of the pericarp and forming the main point of water entry. We reject the hypothesis that G. coronaria cypselae have physical dormancy. Instead, water uptake and germination are impeded by: (1) directed water uptake, mainly through a pericarp-spanning channel-like structure; and (2) mechanical constraint on embryo growth exerted by the hard pericarp. The channel-like structure forms the principal system for controlling seed germination.

Non-deep simple morphophysiological dormancy in seeds of Cheirodendron trigynum (Araliaceae) from the montane zone of Hawaii

AbstractThe Araliaceae is known to have seeds with underdeveloped embryos that must grow prior to radicle emergence, and thus they have morphological (MD) or morphophysiological (MPD) dormancy. Araliaceae is one of about 15 families with woody species in the tropical montane zone, and in Hawaii 15 species occur in the montane. Our purpose was to determine if seeds of the Hawaiian Araliaceae species Cheirodendron trigynum subsp. trigynum have MD or MPD and, if MPD, what level. In a move-along experiment, some seeds were incubated continuously at 15/6, 20/10 or 25/15°C, while others were moved sequentially from low to high or from high to low temperature regimes. Germination percentages and embryo growth were monitored. Also, the effects of cold and warm stratification on dormancy break were determined. Seeds had physiological dormancy (PD) in addition to small embryos that grew prior to germination, and thus MPD. PD was broken slowly ( ≥ 12 weeks), after which embryos grew rapidly, followed by root and shoot emergence. Embryos grew at temperatures suitable for warm stratification; thus, seeds have Type 1 non-deep simple MPD; the dormancy formula is C1bBb. Seeds from Oahu germinated to 94–100% at 15/6, 20/10 and 25/15°C, while those from the Big Island germinated to high percentages only at 15/6 and 20/10°C. Temperature shifts improved germination of seeds from the Big Island, and movement from either low to high or from high to low temperature regimes was effective in promoting germination. This is the first report of non-deep simple MPD in the Araliaceae.

A potential role for endogenous microflora in dormancy release, cytokinin metabolism and the response to fluridone in Lolium rigidum seeds.

Dormancy in Lolium rigidum (annual ryegrass) seeds can be alleviated by warm stratification in the dark or by application of fluridone, an inhibitor of plant abscisic acid (ABA) biosynthesis via phytoene desaturase. However, germination and absolute ABA concentration are not particularly strongly correlated. The aim of this study was to determine if cytokinins of both plant and bacterial origin are involved in mediating dormancy status and in the response to fluridone. Seeds with normal or greatly decreased (by dry heat pre-treatment) bacterial populations were stratified in the light or dark and in the presence or absence of fluridone in order to modify their dormancy status. Germination was assessed and seed cytokinin concentration and composition were measured in embryo-containing or embryo-free seed portions. Seeds lacking bacteria were no longer able to lose dormancy in the dark unless supplied with exogenous gibberellin or fluridone. Although these seeds showed a dramatic switch from active cytokinin free bases to O-glucosylated storage forms, the concentrations of individual cytokinin species were only weakly correlated to dormancy status. However, cytokinins of apparently bacterial origin were affected by fluridone and light treatment of the seeds. It is probable that resident microflora contribute to dormancy status in L. rigidum seeds via a complex interaction between hormones of both plant and bacterial origin. This interaction needs to be taken into account in studies on endogenous seed hormones or the response of seeds to plant growth regulators.

Non-deep simple morphophysiological dormancy in seeds of Viburnum lantana (Caprifoliaceae), a new dormancy level in the genus Viburnum

Seed germination requirements of Viburnum lantana were investigated by experiments both in the laboratory and outdoors. Embryo length, radicle emergence and shoot emergence were analysed to determine the level of morphophysiological dormancy (MPD) of seeds. Mean embryo length in fresh seeds was 1.30 mm, and required growth to at least 2.51 mm to germinate. The critical embryo length was 4.1 mm. In the laboratory, the embryo reached 3 mm length after 20 weeks of warm-temperature incubation (20/7 or 25/10°C), which in fact represents a combination of warm + cold stratification. In seeds subjected to cold stratification (1.5 or 5°C) for 24 weeks, embryos hardly grew. Gibberellic acid stimulated embryo growth and germination. In the outdoor phenology test, the embryos grew from 1.30 mm, i.e. fresh seeds sown in September, to 2.98 mm at the end of the following March. In the ‘move-along’ test (laboratory), starting with temperatures of warm stratification [i.e. 25/10°C (4 weeks) → 20/7°C (4 weeks) → 15/4°C (4 weeks) → 5°C (12 weeks) → 15/4°C (4 weeks)], and in the outdoor phenology study on seeds exposed to a similar temperature sequence, radicle emergence percentages reached 73% after 28 and 35 weeks, respectively. V. lantana does not exhibit a delay between root and shoot emergence, dismissing any kind of epicotyl dormancy. Seeds of V. lantana have non-deep simple MPD, a level not detected previously in the genus Viburnum, with the physiological dormancy component overcome by a combination of warm and cold stratification, preferably in that order.

Dormancy-Breaking Requirements and Germination for Seeds of &lt;i&gt; Ostrya carpinifolia&lt;/i&gt; Scop.

The present research aims at investigating the combined effects of warm stratification (WS)+cold stratification (CS), and gibberellic acid (GA 3 )+cold stratification (CS) on breaking dormancy and germination in seeds of Ostrya carpinifolia . The seeds were subjected to WS (20-25 ÂoC) for 0, 1 and 2 months and were subsequently cold stratified at 3-5 ÂoC for 0, 1, 2, 3 and 4 months (1st experiment). A further amount of seeds was treated with 500, 1000 or 2000 ppm GA 3 for 30 hours and then cold stratified at 3-5 ÂoC for 0, 1, 2, 3 and 4 months (2nd experiment). No germination was observed in the seeds subjected to only WS (1 and 2 months) or CS for 1 month indicating that the seeds of O. carpinifolia are dormant . A 4-month stratification (1 month WS+3 month CS or 4 month CS) fully released dormancy and led to a high germination percentage (94.17 and 98.34% respectively) in a short time (7.12 and 7.00 days respectively). Warm stratification treatment prior to CS, was not required in order to break the seed dormancy of O. carpinifolia and also did not reduce the length of the (total) stratification period required for breaking seed dormancy. Gibberellic acid (GA 3 ) application entirely replaced the CS period required for breaking seed dormancy. The germination of the seeds treated only with 2000 ppm GA 3 (0 months of CS) was (94.17%) as high as the germination of the seeds subjected to 4 months of CS (98.34%). It is obvious that the seedcoat of O. carpinifolia seeds was permeable to GA 3 and did not mechanically restrict embryo growth, thus, the seeds did not exhibit physical dormancy. Based on dormancy breaking requirements, the O. carpinifolia seeds displayed intermediate physiological dormancy.

Taiwanese montaneSambucus chinensisseeds require warm stratification, contrasting with other congeneric temperate members

AbstractMany temperate plant genera, likeSambucus, have species with range disjunctions among North America, Europe and/or Asia. Cold stratification (sometimes in combination with warm stratification) is the primary mechanism to break seed dormancy in these species. For some of these genera showing Northern Hemispheric disjunctions, members also occur in subtropical or tropical regions, mostly confined to higher elevations where climate and vegetation differ from those in northern latitudes. We made two hypotheses concerning germination for the subtropical TaiwaneseSambucus chinensis: (1) seeds from populations exposed to warm temperatures would require warm stratification, and (2) seeds from populations exposed to cold temperatures need cold stratification. We investigated the germination (including embryo growth) of non-stratified seeds over a range of temperatures and tested the effects of cold stratification and of gibberellins GA3and GA4on germination. The amount and timing of germination among populations varied substantially in response to temperature treatments. Seeds from all populations of this species required warm temperatures for dormancy break and germination, regardless of environmental conditions. As such, the majority of seeds had non-deep simple morphophysiological dormancy, which, until now, has not been reported in any members ofSambucus. The seed characteristics of the subtropicalS. chinensisare different from those of temperate members of the genus in which cold stratification is the predominate treatment to overcome dormancy.

Changes in seed dormancy ofRosa multibracteataHemsl. &amp; E. H. Wilson with increasing elevation in an arid valley in the eastern Tibetan Plateau

AbstractVariations in levels of seed dormancy among conspecific populations are poorly understood. We aim to determine the variations in the level of dormancy inRosa multibracteataalong an elevational gradient, and to analyze the mechanisms underlying seed dormancy. The study was conducted in an arid valley in the eastern Tibetan Plateau at five elevations: 1700, 1900, 2100, 2300 and 2500 m. Achene traits were measured and physiological levels of dormancy were determined by measuring germination percentages of achenes treated with H2SO4scarification, warm stratification and cold stratification and combinations of those treatments. Achene size, mass and pericarp thickness increased with increasing elevation, but embryo width decreased with increasing in the arid valley. The level of dormancy generally increased with increasing elevation. The level of dormancy of the rose achenes is intermediate from sites at elevations of 1700, 1900 and 2100 m and deep at elevations of 2300 and 2500 m. Comprehensive analysis suggests that the elevational pattern of level of seed dormancy could be ascribed to intrinsically thicker pericarp and deeper physiological dormancy in the embryo, and extrinsically decreased temperature, increased precipitation and soil moisture at the higher elevations. The great variations of achene traits and levels of seed dormancy across elevations suggest a phenotypic differentiation exists within this rose species. Thus, habitat conditions and achene traits should be considered when selecting roses as materials used to propagate seedlings for ornamental purposes or plant restoration.

A dynamic-bioenergetics model to assess depth selection and reproductive growth by lake trout (Salvelinus namaycush)

We coupled dynamic optimization and bioenergetics models to assess the assumption that lake trout (Salvelinus namaycush) depth distribution is structured by temperature, food availability, and predation risk to maximize reproductive mass by autumn spawning. Because the model uses empirical daily thermal-depth profiles recorded in a small boreal shield lake (lake 373 at the Experimental Lakes Area, northwestern Ontario) during 2 years of contrasting thermal stratification patterns, we also assessed how climate-mediated changes in lakes may affect the vertical distribution, growth, and fitness of lake trout, a cold-water top predator. The depths of acoustic-tagged lake trout were recorded concurrently with thermal-depth profiles and were compared to model output, enabling an assessment of model performance in relation to the observed fish behavior and contrasting thermal conditions. The depths and temperatures occupied by simulated fish most closely resembled those of the tagged fish when risk of predation was included in the model, indicating the model may incorporate the most important underlying mechanisms that determine lake trout depth. Annual differences suggest less use of shallow (warm), productive habitats, resulting in markedly less reproductive mass, during the year with the warm stratification pattern. Mass for reproduction may be lower in warmer conditions because of reduced reproductive investment, yet survival may be inadvertently higher because risky surface waters may be avoided more often in warmer, shallower, and metabolically costly conditions. At a minimum our study suggests that lake trout reproductive mass and fitness may be expected to change under the anticipated longer and warmer stratification patterns.

Factors Influencing Germination of a Functionally Important Grassland Plant, Iris tenax

Grassland prairies of western Oregon and Washington are among the most endangered ecosystems in the United States. Active management and restoration are needed to promote biodiversity in the region. To support plant production for use in habitat restoration, we developed germination protocols for greenhouse propagation of Iris tenax (Oregon iris). Dormancy was most effectively overcome (63% germination) by four weeks of warm stratification at 20/30°C followed by 6–12 weeks of cold stratification at 5°C suggesting that I. tenax may have morphophysiological dormancy. This result was consistent across multiple source populations.

Seed dormancy and germination in three Crocus ser. Verni species (Iridaceae): implications for evolution of dormancy within the genus

The aim of this work was to examine whether seed ecophysiological traits in three closely related Crocus species were associated with ecological niche differentiation and species divergence. Seeds of the temperate tetraploid cytotype of Crocus neapolitanus, the sub-Mediterranean C.etruscus and the Mediterranean C.ilvensis were placed either on agar in the laboratory under different periods of simulated seasonal conditions or in nylon mesh bags buried outdoors to examine embryo growth, radicle and shoot emergence. In agreement with the phenology observed outdoors, in the laboratory embryos required a cool temperature (ca. 10°C) to grow to full size (embryo length:seed length, E:S ratio ca. 0.75) but only after seeds received a warm stratification; radicle emergence then followed immediately (November). Shoot emergence is a temporally separated phase (March) that was promoted by cold stratification in C.neapolitanus while in the other two species this time lag was attributed to a slow continuous developmental process. These species have similar embryo growth and radicle phenology but differ in their degree of epicotyl dormancy, which is related to the length of local winter. Conclusions from laboratory experiments that only consider root emergence could be misleading; evaluating the phenology of both root and shoot emergence should be considered in order to demonstrate ecologically meaningful differences in germination behaviour and to develop effective propagation protocols. Although these taxa resulted from recent speciation processes, the outcomes suggest an early onset of adaptation to local ecological factors and that phylogeny may represent a significant constraint in the evolution and expression of seed traits in Crocus.

Interpopulation variability on embryo growth, seed dormancy break, and germination in the endangered Iberian daffodil Narcissus eugeniae (Amaryllidaceae)

AbstractThe main goal of the study was to assess germination requirements in a threatened daffodil to elaborate a detailed protocol for plant production from seeds, a key tool for conservation. Experiments were carried out both in the laboratory and outdoor conditions. In Pseudonarcissi section, endemic Iberian species of Narcissus studied heretofore have different levels of morphophysiological dormancy (MPD). Embryo length, radicle emergence, and shoot emergence were analyzed to determine the level of MPD. Both interpopulational variability and seed storage duration were also studied. Mean embryo length in fresh seeds was 1.32 mm and the embryo had to grow until it reached at least 2.00 mm to germinate. Embryo growth occurs during warm stratification, after which the radicle emerges when temperatures go down. Seed dormancy was broken in the laboratory at 28/14°C in darkness followed by 15/4°C, but the germination percentage varies depending on the population. In outdoor conditions, seed dispersal occurs in June, the embryo grows during the summer and then the radicle emerges in autumn. The radicle system continues to grow during the winter months, but the shoot does not emerge until the beginning of the spring because it is physiologically dormant and requires a cold period to break dormancy. Early cold temperatures interrupt embryo growth and induce dormancy in seeds with an advanced embryo development. Seeds of N. eugeniae have deep simple epicotyl MPD. In addition, we found that embryo growth and germination were improved by seed storage duration.

Qualitative changes and dynamics of protein synthesis during cold and warm stratification of Norway maple (Acer platanoides L.) seeds

Protein synthesis in cotyledons and embryo axes of Norway maple (&lt;em&gt;Acer platanoides&lt;/em&gt; L.) was studied in seeds stratified at 3 or 15&lt;sup&gt;o&lt;/sup&gt;C. At 3&lt;sup&gt;o&lt;/sup&gt;C stratification, germination of seeds starts after 9 weeks, at 15&lt;sup&gt;o&lt;/sup&gt;C stratification germination does not occur. The changes of protein synthesis level in both temperatures had two phasic character. In embryo axes (3 and 15&lt;sup&gt;o&lt;/sup&gt;C) protein synthesis grow up, but in cotyledons (3&lt;sup&gt;o&lt;/sup&gt;C) synthesis of proteins decrease. Generally, activity of protein synthesis was higher at 3&lt;sup&gt;o&lt;/sup&gt;C, as like as DNA level was higher. After imbibition, in cold and warm stratification, in embryo axes, many new protein are become visible. We expect, that two from this proteins, determined as A and B my be connected with the releasing from dormancy. In seeds stratified at 15&lt;sup&gt;o&lt;/sup&gt;C, these proteins are occuring in vestigal amount or are completely absent.

Qualitative changes in the proteins of cotyledons during cold and warm stratification of Acer platanoides seeds

In Norway maple (&lt;em&gt;Acer platanoides&lt;/em&gt; L.) seeds, during dormancy breakage there appeared some qualitative changes in protein composition of the cotyledons. After 48h of soaking and in the first week of stratification, the number of different proteins decreased. This decrease in number of proteins was probably associated with the effect of hydration of embryo tissue. Protein patterns from imbibed seeds exposed to cold (3&lt;sup&gt;o&lt;/sup&gt;C) and warm (15&lt;sup&gt;o&lt;/sup&gt;C) treatments were not significantly different. The influence of temperature on protein patterns became visible in the third week of stratification, when a few new proteins appeared. One of them, designated B, appeared only during cold stratification before radicles protrusion. They were also present in seeds that had completed germination. These proteins are presumably associated with the process of dormancy breakage.