Cold Stratification Treatments Research Articles

Seed Dormancy Class and Germination Characteristics of Berberis amurensis var. latifolia Nakai, Native to Korea

Berberis amurensis var. latifolia Nakai is a plant native to the Ulleung Island in Korea. In this study, we aimed to identify seed dormancy-breaking and germination requirements of this species using water imbibition experiments, gibberellic acid (GA3) treatment (0, 10, 100, or 1000 mg/L), cold stratification (0, 2, 4, 8, or 12 weeks at 5 °C), move-along experiments, and phenological studies. In the water imbibition experiment, the seed weight increased by more than 120% after 24 h. Analysis of the internal morphological characteristics of the seeds revealed that the embryo in freshly matured seeds was fully grown and did not grow thereafter. The final germination percentages after 12 weeks of cold stratification at 5 °C were 49 ± 6.4% and 63 ± 3.4% under light and dark conditions, respectively. In move-along and phenological studies, a longer cold stratification treatment period resulted in a higher germination percentage; however, the warm stratification treatment did not affect germination significantly. The GA3 treatment had little effect on seed germination. Therefore, we concluded that B. amurensis var. latifolia seeds have intermediate physiological dormancy, and pre-treatment with cold stratification for 12 weeks and incubation in the dark are required for effective seed propagation.

Influence of shade and cold stratification on germination success of vegetative propagules from multiple Butomus umbellatus genotypes

Three experimental trials were conducted to investigate the influence of shade and cold stratification on germination success of vegetative propagules from multiple Butomus umbellatus genotypes. Shade level did not significantly impact germination of propagules in trial 1 (p=0.16); however, significant differences (p<0.0001) in germination percentages at the conclusion of the study were detected between genotypes. Rhizome segments of the triploid genotype one (G1) had the highest mean germination (95±1%); whereas bulbils of the diploid genotypes three (G3), four (G4), and five (G5) germinated to 9±2%, 1±1%, and 15±2%, respectively. Trial 2 focused on bulbils from G3, G4, and G5 diploid plants that were stratified at 4℃ for 35d. Like Trial 1, shade level was not significant (p=0.19) relative to the overall germination of cold-stratified bulbils. However, cold-stratified bulbils exhibited a much higher mean germination (≥93%) for all three genotypes. In Trial 3, the cold stratification treatments were significant and positively correlated to overall germination for G4 (p=0.005, r=0.77) and G5 (p=0.002, r=0.82), but not G3 (p=0.22, r=0.40) bulbils. Germination time significantly differed between genotypes in all cold-stratification treatments except for the 0, 120, and 180-day treatments. These studies demonstrate that a high percentage of vegetative propagules produced by B. umbellatus are capable of successfully germinating under laboratory conditions, but some require extended periods of cold exposure. Given that a single diploid bulbil can produce thousands of bulbils within a growing season; long term management of this species will need to be focused towards limiting bulbil production.

Seed Germination and Growth Improvement for Early Maturing Pear Breeding.

Breeding early maturing cultivars is one of the most important objectives in pear breeding. Very early maturing pears provide an excellent parental material for crossing, but the immature embryo and low seed germination of their hybrid progenies often limit the selection and breeding of new early maturing pear cultivars. In this study, we choose a very early maturing pear cultivar 'Pearl Pear' as the study object and investigate the effects of cold stratification, the culture medium, and the seed coat on the germination and growth of early maturing pear seeds. Our results show that cold stratification (4 °C) treatment could significantly improve the germination rates of early maturing pear seeds. A total of 100 days of cold-temperature treatment in 4 °C and in vitro germination on White medium increased the germination rate to 84.54%. We also observed that seed coat removal improved the germination of early maturing pear seeds, with middle seed coat removal representing the optimal method, with a high germination rate and low contamination. The results of our study led to the establishment of an improved protocol for the germination of early maturing pear, which will greatly facilitate the breeding of new very early maturing pear cultivars.

Cultivar and Maternal Plant Environment Influence Cold Stratification Requirements and Germination Rates of Vitis Species

Open-pollinated seeds from grapevines in Parlier and Davis (in California) and Geneva (in New York) were collected in 2016, 2017, and 2018. Seeds were subjected to a series of cold stratification treatments of varying lengths and germinated in incubators to compare germination rates. Two V. vinifera cultivars (Chardonnay and Cabernet Sauvignon) and three other cultivars (V. labrusca hybrids) with a similar genetic background were compared across three locations to test for maternal environmental effects on germination rates under different cold stratification durations. Two interspecific hybrids (‘Salamander’ and ‘Sovereign Rose’) and three genotypes each from two species, V. riparia and V. cinerea, were evaluated to compare germination rate variability at different cold stratification durations among and within species and hybrids. Large variability in germination rates was evident among and within grape species, with some accessions requiring little to no cold stratification, and others requiring 10 to 12 weeks. These differences could be useful for breeding grapevines with high or low dormancy requirements. The maternal plant environment impacted the seed weight and total seed germination across years and locations.

A REVIEW OF BREAKING SEED DORMANCY IN HAWTHORNS (CRATAEGUSSPP.)

Propagation of hawthorns (Crataegusspp.) is difficult, and vegetative methods are not responsive in a sufficient manner. So, seed propagation is prevalently used to propagate hawthorns. However, hard endocarp and embryo dormancy restrict the germination of hawthorns. To overcome these restrictions, many treatments have been tested in the researches. Some of them were magnificent and others ineffective. It has been resolved that warm and cold stratification are the best for breaking dormancy in seeds of hawthorns. Thus far, no substitution has been found for warm and cold stratification treatment to release the seeds of hawthorns from dormancy, from the conventional point of view. Besides, combination with other factors may reduce the period and temperature degrees of warm and cold stratification, for instance, species, eliminating endocarp, treatment with growth regulators, and chemical scarification. In this review, the results of methods will be referred to that used in the studies to break seed dormancy in hawthorns.

Physiological Dormancy and Germination Characteristics of Maianthemum dilatatum (A. W. Wood) A. Nelson and J. F. Macbr. (Asparagaceae)

This study was conducted to elucidate the germination characteristics and dormancy types in Maianthemum dilatatum (A. W. Wood) A. Nelson and J. F. Macbr. M. dilatatum seeds were collected from the Nari Basin on Ulleungdo Island, South Korea and used in a water imbibition test; the seed weight increased by approximately 20% within 48 h. The embryo-to-seed ratio at the time of seed dispersal was 0.57 ± 0.03. When the seeds were incubated under light and dark conditions, they germinated under dark conditions, and the germination rate was higher at 25 °C than at 20 °C. However, the final germination rates under dark conditions were 27.4 ± 3.6 and 47.1 ± 7.6%, respectively. Under 4, 8, 12, and 16 weeks of cold stratification treatment, the highest germination rate of 83.6 ± 3.6% was observed at 25 °C at 12 weeks of cold stratification treatment, the germination start date was decreased by more than 10 d, and the mean germination time (MGT) was shortened from 50 d to 39 d. However, the germination rate, germination start date, and MGT did not differ significantly among the gibberellic acid hormone treatments. Therefore, it was evident that M. dilatatum demonstrated physiological dormancy (PD) that can broken by cold stratification treatment and dark conditions.

Exogenous gibberellin can effectively and rapidly break intermediate physiological dormancy of Amsonia elliptica seeds.

Accelerated global warming is leading to the loss of plant species diversity, and ex situ preservation of seeds is becoming an increasingly important aspect of species conservation. However, information on dormancy and germination is lacking in many endangered species. Amsonia elliptica (Apocynaceae) is the only Amsonia species native to Korea, and the South Korean Ministry of Environment has designated it Class II endangered wildlife. Nevertheless, the dormancy class and the dormancy breaking method for seeds of this species for germination are not precisely known. We identified the structure of A. elliptica seeds and the causes of dormancy, which inhibits germination. In addition, we tried to develop an effective germination promotion method by testing the wet stratified condition, which breaks dormancy, and the form of gibberellin that can replace it. Fresh seeds of A. elliptica imbibe water, but the covering layers (endosperm and seed coat) inhibit germination by mechanically restricting the embryo. Initial germination tests confirmed low embryo growth potential and physiological dormancy (PD). Restriction due to the covering layer was eliminated by seed scarification, and abnormal germination was observed. After 12 weeks of cold moist stratification at 4°C, only 12% of seeds germinated. However, 68.8% of seeds subjected to 8 weeks of warm moist stratification followed by 12 weeks of cold stratification germinated, indicating that warm stratification pretreatment before cold stratification is effective in breaking dormancy. A. elliptica seeds exhibited intermediate PD. Furthermore, 61.3% of seeds soaked in 500 mg/L GA4+7 for 14 days and incubated at 25/15°C germinated. Therefore, GA4+7 rapidly broke the dormancy of A. elliptica seeds compared with warm plus cold stratification treatment, thus providing an efficient method for seedling production.

Propagación de Arctostaphylos pungens Kunt procedente de bosques templados del centro-norte de México

Introduction:Arctostaphylos pungens Kunt is a species with significant characteristics for restoration; however, there are few studies on its propagation. Objective: To evaluate the effect of pre-germinative treatments and the use of vegetative propagation methods in A. pungens. Materials and methods: Eight pre-germinative treatments were evaluated, consisting of scarification with H2SO4 (98 %) for 5 and 6 h, gibberellic acid immersion (1 000 ppm), cold stratification (4 °C for 30, 60 and 90 days) and heat shock (100 °C for 5 min), as well as combinations of these. Vegetative propagation was analyzed by cuttings and air layering. Results and discussion: The highest germination (73.33 ± 15.63 %) was for immersion in H2SO4 for 5 to 6 h; heat shock and cold stratification treatments showed low or no germination. Root formation was not achieved in cuttings but was achieved in 37.50 ± 25 % of 20-week air layering. Conclusion: The best treatments consisted of immersion in H2SO4. It is recommended to continue experimenting with vegetative propagation by leaving air layering for more than the 20 weeks used in this study to achieve complete root development.

The sweet and musky scent of home: biogenic ethylene fine-tunes seed germination in wetlands.

Wetlands are known for comparatively high production of biogenic ethylene from decomposed sediment. Because the gas has various well-documented effects on seed physiology, we asked whether it can be a vital seed germination cue for wetland plants. Specifically, we explored whether ethylene plays an ecological role in (i) breaking/weakening seed dormancy, (ii) broadening the germination niche width, (iii) promoting germination speed or (iv) altering the germination requirements of six plant species with different occurrence along a hydroperiod gradient. In a factorial experiment, both ethylene-treated and untreated seeds were incubated in combinations of temperature (constant versus fluctuating), illumination (light versus darkness) and oxygen (aerobic versus hypoxia) with and without cold stratification. Our results revealed seed exposure to ethylene did not weaken or break dormancy without cold stratification treatment. However, ethylene helped to broaden the germination niche width, increased overall germination percentage and speed of cold-stratified (non-dormant) seeds. This indicates that ethylene helps those seeds that lost dormancy (non-dormant) to sense favourable water-saturated versus flooded substrate depending on their requirement for aerobic versus hypoxic conditions to trigger germination. We conclude that ethylene does not interfere directly with the dormancy-breaking process in autumn-dispersed seeds that are naturally cold-stratified in winter and germinate in spring/summer. However, ethylene plays a crucial ecological role as a 'flood detector' for different wetland plant communities (reed, mudflat, swamp, shallow water) to synchronize germination of non-dormant seeds in the most suitable habitat at the right time.

Sulfuric Acid and Gibberellic Acid (GA3) Treatment Combined with Exposure to Cold Temperature Modulates Seed Proteins during Breaking of Dormancy to Germination in Tilia miqueliana.

Tilia miqueliana produces woody seeds that exhibit deep dormancy. In this study, we used cell biology methods, including Paraffin section determination and Coomassie brilliant blue staining, as well as proteomics-based methods, including two-dimensional electrophoresis with matrix-assisted laser desorption/ionisation tandem time-of-flight mass spectrometry (2DE-MALDI-TOF/TOF), to examine the effects of H2SO4-GA3 and cold stratification (3°C) treatment on proteins during dormancy release and germination in T. miqueliana seeds. The results revealed that during cold stratification, the area and density of proteins in the endosperm cells of H2SO4-GA3-treated seeds were significantly altered. Total protein content was continuously consumed and utilised. Storage proteins (albumin, globulin, prolamin, and glutelin) were degraded to varying degrees. Sixteen differential proteins were identified using mass spectrometry. Kyoto encyclopedia of genes (KEGG) pathway analysis revealed that the glycolysis/gluconeogenesis, secondary metabolite biosynthesis, glyoxylate and dicarboxylate metabolism, amino acid biosynthesis, and metabolic pathways were critical during dormancy release and germination. Gene ontology analysis and KEGG pathway annotation of differential proteins in the co-expression network indicated that the differential proteins are implicated in photosynthesis, glucose metabolism, biosynthesis of plant hormones, and glycolysis/gluconeogenesis. Synergistic interactions among these proteins accelerated dormancy release and germination. Therefore, H2SO4-GA3 cold stratification treatment is the best method for achieving rapid dormancy release and increasing the germination rate of T. miqueliana seeds.

Germination of Pulsatilla cernua var. koreana Seeds as Influenced by Harvest Dates and Development of Seeds Analyzed by X-ray Imaging

Pulsatilla cernua var. koreana seeds were harvested at six different dates between 16 days after flowering (DAF) (8 Apr.) and 43 DAF (5 May) in 2018 and categorized into six groups based on X-ray images. Germination tests were performed without and with 2 weeks of moist 5 °C treatment [cold stratification (CS)]. Seeds harvested at 38 DAF (30 Apr.) with well-developed vegetative organs (embryo and endosperm) in seeds categorized as A and B (seed A and seed B, respectively) based on the X-ray images were considered fully developed, and 80% of seeds were considered mature. However, the germination rates were less than 26% or 28% when full seeds harvested at 43 DAF received no or 14 days of CS treatment, respectively. Our study suggests that the low germination rate of fully developed seeds as judged by X-ray images showing well-developed embryo and endosperm could result from the presence of dormancy that was not broken effectively by 14 days of CS coupled with the loss of viability caused by 8 months of dry storage at 5 °C.

Factors Affecting Seed Germination and Establishment of an Efficient Germination Method in Sugar Pine (Pinus lambertiana Dougl.)

Mature sugar pine (Pinus lambertiana Dougl.) trees produce large amounts of viable seeds but have seed dormancy. In this study, we used three sugar pine genotypes, 8877, 9306, and 9375, to test seed germination response. Seed germination from local sources varied greatly, and germination percentages were poor. There was a large variation in seed size and seed weight among the genotypes. Seeds of 9375 and 9306 were significantly larger and heavier (30.7 and 28.8 g/100 seeds, respectively) than 8877 (23.6 g/100 seeds). Three types of seeds—intact seeds, hulled seeds, and naked embryos—were examined for germination. Intact seeds failed to germinate due to the physical restraint and water impermeability of the seed. Chemical scarification with 5 m hydrochloric acid and 5 m sodium hydroxide did not soften the hard seedcoat and also failed to induce any germination of intact seeds. Hulled seeds resulted in an extremely low germination percentage (≤5%) with abnormal seedling development even though the endosperm was water permeable. Germination of the hulled seeds was not increased by adding 1 mg·L−1 gibberellic acid to the culture medium. Artificial opening of the hulled seeds created by longitudinal or horizontal cuts on the endosperm after removal of the seedcoat to avoid physical restraint and allow air exchange also failed to improve germination, indicating that inhibitors related to germination were present in the endosperm. However, naked embryos of all three genotypes germinated rapidly and uniformly with 70% to 95% germination percentage regardless of cold stratification treatment. Our data indicate that sugar pine seeds from the current source did not have physiological dormancy of embryos themselves, but dormancy was imposed by the seedcoat and endosperm. Using the naked embryos as donor explants, we have successfully established an efficient in vitro culture system. The protocol described here can be applied for the tissue culture and genetic transformation of sugar pine.

Using genetic evaluation to guide conservation of remnant Juniperus communis (Cupressaceae) populations

Many critically endangered plant species exist in small, genetically depauperate or inbred populations, making assisted gene flow interventions necessary for long-term population viability. However, before such interventions are implemented, conservation practitioners must consider the genetic and demographic status of extant populations, which are strongly affected by species' life-history traits. In northwestern Europe, Juniperus communis, a dioecious, wind-pollinated and bird-dispersed gymnosperm, has been declining for the past century and largely exists in small, isolated and senescent populations. To provide useful recommendations for a recovery plan involving translocation of plants, we investigated genetic diversity and structure of populations in Belgium using four microsatellite and five plastid single-nucleotide polymorphism (SNP) markers. We detected no clonality in the populations, suggesting predominantly sexual reproduction. Populations exhibited high genetic diversity (He =0.367-0.563) and low to moderate genetic differentiation (FST ≤0.133), with no clear geographic structure. Highly positive inbreeding coefficients (FIS =0.221-0.507) were explained by null alleles, population substructuring and biparental inbreeding. No isolation by distance was observed among distant populations, but isolation at close geographic proximity was found. Patterns were consistent with high historical gene flow through pollen and seed dispersal at both short and long distances. We also tested four pre-germination treatments among populations to improve germination rates; however, germination rates remained low and only cold-stratification treatments induced germination in some populations. To bolster population regeneration, introductions of cuttings from several source populations are recommended, in combination with in situ management practices that improve seedling survival and with ex situ propagation.

Functional variants of DOG1 control seed chilling responses and variation in seasonal life-history strategies in Arabidopsis thaliana.

The seasonal timing of seed germination determines a plant's realized environmental niche, and is important for adaptation to climate. The timing of seasonal germination depends on patterns of seed dormancy release or induction by cold and interacts with flowering-time variation to construct different seasonal life histories. To characterize the genetic basis and climatic associations of natural variation in seed chilling responses and associated life-history syndromes, we selected 559 fully sequenced accessions of the model annual species Arabidopsis thaliana from across a wide climate range and scored each for seed germination across a range of 13 cold stratification treatments, as well as the timing of flowering and senescence. Germination strategies varied continuously along 2 major axes: 1) Overall germination fraction and 2) induction vs. release of dormancy by cold. Natural variation in seed responses to chilling was correlated with flowering time and senescence to create a range of seasonal life-history syndromes. Genome-wide association identified several loci associated with natural variation in seed chilling responses, including a known functional polymorphism in the self-binding domain of the candidate gene DOG1. A phylogeny of DOG1 haplotypes revealed ancient divergence of these functional variants associated with periods of Pleistocene climate change, and Gradient Forest analysis showed that allele turnover of candidate SNPs was significantly associated with climate gradients. These results provide evidence that A. thaliana's germination niche and correlated life-history syndromes are shaped by past climate cycles, as well as local adaptation to contemporary climate.

EFFECT OF COLD STRATIFICATION ON SEED GERMINATION OF THE MULTIPURPOSE FRUIT SHRUB, ZIZIPHUS LOTUS (L.) LAM. (RHAMNACEAE)

Shrubs and trees of the genus Ziziphus are a good example of naturally occurring multipurpose plant species with great potential in arid regions. This study was conducted to investigate the effect of cold stratification on seed germination and seedling growth of Ziziphus lotus (L.) Lam. Seeds were subjected to 0, 45, 90 and 120 days of cold stratification at 5°C. We also examined fruit, kernel and seed morphology. For each treatment period, four replicates of 50 seeds were incubated in plastic containers between two layers of moist sand at 15% and under greenhouse conditions for 15-day period. At the end of the experiment, the final germination percentage (FGP), shoot length and root length were assessed. The results clearly indicated that increasing duration of cold stratification improved seed germination. The most effective stratification period was 120 days where Z. lotus recorded 83% of FGP and 16.5 cm of total seedling length. Cold stratification treatments significantly increased shoot height, root length, as well as seedling total length. 120 days stratification treatment resulted in the highest shoot and root length (6.80 cm and 9.75 cm, respectively). An overview on the emergence of Z. lotus seedlings during a 15-day period was also illustrated.

Germination of Pulsatilla Seeds as Influenced by Seed Morphology, Moist 5 °C and Gibberellin (GA3) Treatment, and Detection of Nickel in Seeds

Seeds of Pulsatilla turczaninovii were categorized to full and empty seeds based on observations under a light microscope and on X-ray images. A germination test for full or empty seeds was evaluated as affected by the duration of gibberellin GA3 and the moist 5 °C cold stratification (CS) treatment. The morphological and elemental components of P. turczaninovii and P. cernua var. koreana seeds were analyzed using low-temperature scanning electron microscopy (LT-SEM) and energy dispersive X-ray diffraction analysis. The results showed that 64% of full and semifull P. turczaninovii seeds 10 weeks after harvesting germinated in 17 to 19 days; however, the germination rate, including empty and semiempty seeds, was lower (52.6%). Full seeds with damaged or dried vegetative organs (embryo or endosperm) and semifull seeds with severely damaged vegetative organs were observed, and this result could be related to low germination rates. Germination patterns of seeds stored dry at 5 °C for 44 weeks that showed a sigmoid pattern were increased by immersing seeds in a GA3 solution for 8 hours and treating seeds with 16 or 32 days of CS. More seeds germinated between 12 and 17 days (as compared with 17 to 29 days), especially when they were treated with GA3 and received 32 days of CS. Comparison of germination rates of visually full seeds upon harvest (52.6%) with those that had been stored dry for 44 weeks (26.3% to 29.7%) suggested that the viability of seeds may have decreased. Dormancy could be a factor that decreased germination and can be removed by low temperature and GA3 treatment. LT-SEM revealed a valley-like, sunken streak in empty seeds of P. cernua var. koreana. The nickel content in the trichome and seedcoat of full and empty seeds of both taxa ranged from 2.98 to 4.62 (weight %), as determined on X-ray images. Our study suggested that the low germination rate was due to either the presence of dormancy, damage to either embryo or endosperm, a loss in viability, or the presence of nickel in the seeds.

Propagation of Shinnery Oak as a Framework for Restoration

Shinnery oak (Quercus havardii) is a native clonal shrub that contributes to an imperiled biotic community in the southern Great Plains of North America. Nevertheless, there is little information on shinnery oak ecology and this lack of information hinders potential restoration of shinnery oak in areas where it has been eliminated. We provide findings from a study conducted to assess emergence and seedling survival from acorns collected in western Oklahoma in 2016. We observed that cold stratification treatments (i.e., acorns stored at 2°C for 2 weeks) and greater acorn size resulted in higher emergence. Although we found no effect of acorn size on seedling survival, we observed that shade reduced seedling survival (P < 0.005). Our study provides previously unknown information on several fundamental aspects of shinnery oak ecology and offers a baseline for restoration efforts by documenting successful shinnery oak emergence and factors associated with seedling survival.

Effect of pre-sowing treatments on seed germination and seedling vigour index of Abies spectabilis (D.Don) spach

An experiment was conducted to study the effect of pre-sowing treatments on germination of Abies spectabilis commonly called as “Talispatra” - an important high level conifer of Western Himalayan region. The seeds of Abies spectabilis collected from Kalabagh near Churdhar area of Shimla district (H.P.) were given different pre-sowing treatments of cold moist stratification in sand for 1 to 4 weeks and control (untreated seeds) to study their effect on germination behaviour and seedling vigour index. Significant differences were observed in germination per cent and seedling vigour index of seeds subjected to different pre-sowing treatments. The maximum germination per cent (42.00%) was recorded in seeds treated with cold moist stratification treatment in sand for 1 week followed by 36.00 per cent germination recorded for control (untreated seeds). The minimum germination per cent (19.50%) was recorded in seeds treated with cold moist stratification treatment in sand for 4 weeks. The findings of the present investigation revealed that Abies spectabilis seeds do not possess any dormancy and the poor germination is primarily due to presence of large number of empty seeds.

Germination of Fully Developed Corylopsis Seeds Influenced by Harvest Date and Cold Stratification

Corylopsis seed germination tests were conducted to assess the influence of harvest date (seed maturity) and cold stratification (CS) at 5 °C. Corylopsis gotoana seeds harvested on 12 July, 2 and 22 Aug., 6 and 20 Sept., and 1 and 10 Oct. 2011 were immersed in water for 20 min to separate fully developed seeds (full seeds) from empty seeds by floatation, and by X-ray scanning to identify full from empty seeds (Expt. 1). Immersing seeds in water did not effectively separate full seeds from empty seeds as evaluated by seed germination tests. Seeds harvested on or around 6 Sept. that sank showed translucent X-ray images with fully developed internal structures composed of embryo, cotyledons, and endosperm, and were considered mature. Without CS, &gt;12% seeds harvested on 20 Sept. germinated, regardless of whether seeds were full or empty. Seeds of C. coreana harvested on 5 and 15 Sept., and 5 and 18 Oct. were stored dry at 20 °C until 27 Dec. and germinated after 0, 3, 6, 9, and 12 weeks of CS (Expt. 2). Longer than 6 weeks of CS was required to accelerate and increase the germination of seeds harvested on or after 5 Sept. Germination percentage of full seeds harvested on Oct. 18 was increased to &gt;72% as the duration of CS treatment increased to 12 weeks. In conclusion, fully developed seeds harvested on or after 6 Sept. were considered mature and 6 weeks of CS accelerated germination and increased the germination percentage. Further, dormancy of Corylopsis seeds appears to be shallow since germination occurred without any CS.

Effects of pretreatments on seed dormancy and germination in endemic Uludağ flax (Linum olympicum Boiss.) (Linaceae)

Linum olympicum Boiss. (Linaceae) is an endemic species to Turkey, and has both medicinal and ornamental properties. In this study, we investigated the effects of GA3 and cold stratification (1 or 4 months) on the germination and mean germination time in relation to breaking dormancy in this species under darkness (20 °C) and light (20/10 °C, 12/12 h) conditions. Seeds were collected from specimens that spread on limestone or granite screes, ledges of rocky or turfy slopes, and hilltops of the alpine belt from Uludag Mt. (Bursa, Turkey, 2200–2300 m). We show that a combination of hormone and cold stratification treatments promoted seed germination under darkness and light conditions. Non-stratified seeds germinated to 73% following 1000 mg L−1 GA3 treatment and also it was 83% after 1 month cold stratification. After 4 months of cold stratification treatment, 10% and 53.3% of seeds successfully germinated after incubation in light and dark conditions, respectively. Hormone and cold stratification treatments also reduced mean germination time. Our results revealed that seeds of L. olympicum have physiological dormancy and require prolonged time for cold stratification and darkness for germination, rather than responding to the photoperiod. Germination requirements of L. olympicum have not been studied previously, and the data obtained could be used for the ex situ protection of this alpine species.