Non-dormant Seeds Research Articles

Improving seed germination: effect of stratification and dormancy-release priming in Lonicera insularis Nakai

Lonicera insularis Nakai is endemic plant predominantly distributed along the coastlines of Ulleung-do and Dok-do in South Korea, and is significant for medicinal and ornamental uses. However, previous studies reported that L. insularis seeds exhibit morphological dormancy (MD), causing them to germinate only at specific temperatures. Therefore, this study aimed to classify the dormancy type of L. insularis seeds, expand the germination temperature range, and confirm the industrial applicability through dormancy-release (DR) priming. The seeds of L. insularis exhibited no inhibition of water absorption by the seed coat, with 85.0% germination observed at 15°C, similar to the viability (84.0%). Initially, the initial seeds of L. insularis exhibited an embryo-to-seed (E:S) ratio of 0.24 during dispersal, which increased to 0.81 by day 18 at 15°C, indicating that the seeds exhibit MD with underdeveloped embryos. Treatments with GA3 and GA4 + 7 to overcome MD and expand the germination temperature range did not significantly enhance germination. However, seeds that grew embryos through stratification for 2 weeks at 15°C effectively expanded the germination temperature range. Additionally, DR-primed seeds maintained the expanded germination temperature range even after redrying, confirming the commercial potential of DR-primed seeds. Therefore, this study represents the first application of a novel approach to alleviate dormancy in L. insularis seeds through the integration of stratification and priming techniques, termed dormancy-release priming. This approach resulted in a significant increase in germination and expanded the effective temperature range for seed germination. These findings suggest that dormancy-release priming could be a valuable method for producing non-dormant seeds, enhancing the potential for L. insularis distribution and industrial applications.

The seed dormancy profile of three types of vegetation in Golestan National Park in Iran and a comparison with the world database

AbstractDefining the seed dormancy profile (SDP) of plant communities may provide insight into species adaptive mechanisms, community structure, and dynamics. Golestan National Park (GNP) in Iran consists of different types of vegetation, namely deciduous temperate forest, matorral, and steppe in close proximity but with variability of environmental factors. Plant species, life forms, and kinds of seed dormancy were determined in the three vegetation types, and a SDP of types was generated and compared with corresponding ones in the world database. In all GNP vegetation types, 80%–82% and 2%–3% of the species had dormant (D), and nondormant (ND) seeds, respectively, but in 17% the class of dormancy was unknown. Physiological dormancy (PD) was the most abundant followed by physical dormancy (PY). The species percentage with ND seeds in GNP was significantly two or three times lower than that in the world database. The PD percentage in the matorral was significantly higher than that in the world database. The PY percentage was higher in the forests but lower in the matorral and steppe compared with the world database. The morphophysiological (MPD) dormancy percentage was significantly lower in the forests but higher in the matorral and steppe than in the global database. Seed dormancy profiles were not affected by the proximity of vegetation types in the GNP, but they differed from those of the world database for each vegetation type. The past climatic fluctuations associated with the present‐day seasonality of the region might be the selective pressure for the increased percentage of species with D seeds in the GNP.

Proteomic analysis during seed development provides insight into the early establishment of seed dormancy in Xanthium strumarium.

This experiment was carried out to provide a comprehensive insight into the protein activities involved in dormancy establishment in seeds of common cocklebur (Xanthium strumarium), an annual plant with two dimorphic seeds contained in one casing known as a burr. These consist of a smaller dormant seed and a larger non-dormant seed. The proteome profile was compared between developing dormant and non-dormant seeds of Xanthium strumarium at five consecutive stages including three, 10, 20, 30, and 45 days after burr emergence (stages 1 to 5). We identified 6524 proteins in total, and approximately 3.6% of these were differentially abundant proteins (DAPs) between the two seed types. Both seed types showed fundamental changes in developmental programs during the examined stages. More than 38% of all DAPs were observed at the first stage, supporting the importance of the early developmental stage in seed fate determination. The detected DAPs at stage 1 were mainly associated with the cell division phase, which showed a delay in the dormant seeds. Over-representation of proteins responsible for cell wall biosynthesis, cytokinesis, and seed development were detected for non-dormant seeds at the first stage, while dormancy-associated proteins showed less abundance. Stage 3 was the critical stage for switching processes toward seed maturation and abscisic acid (ABA) signaling. Interestingly, higher abundance proteins in the mature non-dormant seed were mainly involved in the facilitation of seed germination. Taken together, the temporal pattern of the accumulated proteins in developing dormant seeds demonstrated a delay in the initiation of active cell division, enriched response to ABA, and defects in seed maturation. Moreover, stored proteins in the mature dormant seed delay germination but not dormancy induction. Finally, our results suggest that dormancy may be established at a stage of seed development earlier than previously thought.

Catalyzing Germination: Exploring Scarification and Hot Water Treatments for Dormancy Breaking and Enhanced Storage in Ficus Benjamina L., Thespesia populnea L., Phyllanthus emblica L., Tectona grandis L.f. seeds

A seed is a significant stage in the plant life cycle and is often referred to as the dispersal unit of the plant. There are two types of seeds: dormant seeds and non-dormant seeds. A dormant seed is one that does not have the capacity to germinate within a definite period under any combination of normal, physical and environmental factors. The other type is favourable for germination and when the seed becomes non-dormant, the circumstances that break dormancy and the location of water gaps in seeds, remain unclear. In the present study, we consider the adaptive role of impermeable coats in the seeds of Ficus Benjamina L., Thespesia populnea L., Phyllanthus emblica L. and Tectona grandis L.f. The study was particularly designed to analyze the conditions that break dormancy and the location of the primary water gap during dormancy breaking. Each seed was treated separately to break its dormancy and it was observed that water entered only through the lens due to the dislodgement of the palisade layer. Additionally, the storage life of Ficus Benjamina L. and Phyllanthus emblica L., seeds was extended as evidenced by the analysis of low moisture content decreasing from 6.02% to 5.31%. This study concludes that the impermeable seed coat of seeds with low moisture content increases storage life and regulates seed imbibition, thus influencing germination with the growing season.

Dormancy, germination, and associated seed ecological traits of 25 Fabaceae species from northern India.

Fabaceae produce seeds with water-impermeable seed coats, i.e., physical dormancy (PY). We hypothesized that the proportion of PY seeds will increase with the dryness of the habitat, and some key seed ecological traits will be strongly associated with different levels of PY. Fresh seed of 25 Fabaceae species collected in northern India were used for imbibition and germination experiments to determine the proportion of seeds with PY and of nondormant (ND) seeds compared to their Sri Lankan congeners. Seed coat:seed mass ratio (SCR), 1000 seed weight, seed shape index (SSI), embryo type and median germination time of ND seeds were determined. Four imbibition and germination patterns were identified among seeds of the studied species. Seeds collected from Indian populations had a higher proportion of PY seeds than those of Sri Lankan populations. We identified a type of embryo called 'spatulate axile' that had not been identified before among the studied species. Species with ND seeds had a lower SCR and a higher SSI than those with PY. Our hypothesis was confirmed since populations from drier habitats in India produce a higher proportion of PY seeds than those from Sri Lanka. A low SCR ensures minimal resistance to germinating seeds, while seeds with a high SSI have a lower tendency to incorporate into the soil seed bank. Thus, these seed traits aid the fast germination of ND seeds, often dispersed just before the rainy season.

A long-term experiment reveals no trade-off between seed persistence and seedling emergence.

Information on seed persistence and seedling emergence from the soil seed bank is critical for understanding species coexistence and predicting community dynamics. However, quantifying seed persistence in the soil is challenging; thus, its association with other life-history traits is poorly known on a broad scale. Using germination phenology for 349 species in a 42-yr experiment, we quantified the persistence-emergence correlations and their associations with intrinsic regeneration traits using Bayesian phylogenetic multilevel models. We showed no trade-off between seed persistence and seedling emergence. Physically dormant seeds were more persistent but exhibited lower emergence than nondormant seeds. Monocarpic species had both higher persistence and emergence than polycarpic species. Seed mass posed a marginal proxy for persistence, while emergence almost doubled from the smallest to the largest seeds. This study challenges the traditional assumption and is the first demonstration of noncorrelation between persistence and emergence, probably owing to the complexity of regenerative strategies. Species with short persistence and low emergence would be the most vulnerable for insitu conservation. Our analyses of this unique, long-term dataset provide a strong incentive for further experimental studies and a rich data resource for future syntheses.

Environmental Regulation of Weed Seed Dormancy and Germination

Many weeds produce dormant seeds that are unable to complete germination under favourable conditions. There are two types of seed dormancy: primary dormancy (innate dormancy), in which seeds are in a dormant state upon release from the parent plant, and secondary dormancy (induced dormancy), in which dormancy develops in seeds through some experience after release from the parent plant. Mechanisms of seed dormancy are categorized as embryo dormancy and coat-imposed dormancy. In embryo dormancy, the control of dormancy resides within the embryo itself, and in coat-imposed dormancy, it is maintained by the structures enclosing the embryo. Many factors can influence seed dormancy during development and after dispersal; they can be abiotic, biotic, or a combination of both. Most weeds deposit a large number of seeds in the seed bank, which can be one of two types—transient or persistent. In the transient type, all viable seeds in the soil germinate or die within one year, and there is no carry-over until a new crop is deposited. In the persistent type, at least some seeds survive in the soil for more than one year and there is always some carry-over until a new crop is deposited. Some dormant seeds require after-ripening—changes in dry seeds that cause or improve germination. Nondormant, viable seeds can germinate if they encounter appropriate conditions. In the face of climate change, including global warming, some weeds produce a large proportion of nondormant seeds, which germinate shortly after dispersal, and a smaller, more transient seed bank. Further studies are required to explore this phenomenon.

Correlation Analysis of Plant Growth Regulators during Development and Germination in the Orthodox, Non-Dormant Seeds of Vigna unguiculata (L.) Walp. (subsp. sesquipedalis)

Correlation Analysis of Plant Growth Regulators during Development and Germination in the Orthodox, Non-Dormant Seeds of Vigna unguiculata (L.) Walp. (subsp. sesquipedalis)

Camel potentiality in survival and germination of wild pastoral species: The case of Fabaceae in Sahara rangelands of Algeria

Previous studies conducted in the Sahara desert have reported the consumption of wild native pastoral plants by camels. To test the hypothesis that camels may effectively break seed dormancy, we collected fresh faeces from different Saharan rangelands frequented by camels.Seeds were extracted from camel faeces and were quantified. Germination of extracted seeds was compared with that of freshly collected seeds under controlled conditions. Sixteen native pastoral species in 8 families and two unidentified species were quantified, with a high proportion of Fabaceae seeds recovered especially Astragalus ghysensis. The Digestive system of camels, effectively (1) broke seed physical dormancy exceptionally for Argyrolobium uniflorum, Astragalus cruciatus and Astragalus ghysensis there by promoting seed germination; (2) enhanced the percentage of germination of non-dormant seeds in Bassia muricata, Erodium glaucophyllum, Fagonia glutinosa and Plantago ciliata and (3) maintained viability but did not contribute to a prompt germination of Cornulaca monacantha seeds. Therefore, camels act as effective dispersers of these Fabaceae species by scattering seeds and promoting germination. We conclude that it is necessary to better understand the role of camels in the maintenance and conservation of the studied species by endozoochory.

Variation in Seed Dormancy of Chaco Seasonally Dry Forest Species: Effects of Seed Traits and Population Environmental Conditions.

The persistence of subtropical seasonally dry forests urgently requires the implementation of ex situ conservation and restoration programs. We studied variation in seed traits and dormancy of six native species growing in seasonally dry Chaco forests of Argentina. We documented high intra- and interspecific variability in seed traits and dormancy. Fresh seeds of Geoffroea decorticans and Parasenegalia visco (Fabaceae) were water-permeable and nondormant (ND), while those of Parkinsonia praecox and Vachellia aroma (Fabaceae) were water-impermeable and had physical dormancy (PY). Seeds of Schnopsis lorentzii (Anacardiaceae) and Sarcomphalus mistol (Rhamnaceae) were water-permeable and had physiological dormancy (PD). Mechanical and chemical scarification were the most effective methods to break PY, and dry storage for 3 months was effective in breaking PD. Seeds of large-seeded species were ND or had PD, and those of small-seeded species had PY. Species inhabiting moist habitats had ND seeds, whereas those from seasonally dry habitats had seeds with PY or PD. These results suggest that seed traits and dormancy are species-specific and that intraspecific variation in seed traits is likely associated with high phenotypic plasticity of species in response to local environmental heterogeneity. These findings should be considered at the time of implementation of conservation techniques and for seed sourcing decisions for restoration.

Review of the Current Research Progress of Seed Germination Inhibitors

Germination inhibitors, which inhibit the germination of seeds, spores and other plant reproductive material, are abundant in the plant kingdom and include phenols, cyanides, alkaloids, essential oils, amino acids, etc. These inhibitors can be classified as germination destructors and germination retarders depending on whether they harm the morphology, structure and physiology of the seed. Germination retarders are closely related to seed dormancy, and exogenous retarders can be used to extend the “dormancy” period of non-dormant seeds or perishable seeds by applying the proper dosage. They have significant potential applications as preservatives for seed preservation following harvest or for the storage of long-term germplasm resources. Germination destructors, as a type of relatively high-efficiency, low-specificity “toxic chemicals”, are of significant benefit in the application of effective and environmentally benign herbicides. At present, the main problems related to the research methods of germination inhibitors include difficulty in determining the specific endogenous substances and the minimum inhibitory concentration to induce dormancy, as well as whether the application of exogenous inhibitors will cause physiological damage to seeds. In the future, we should strengthen the tracking of germination inhibitors, explore the mechanisms of action of specific substances and deeper molecular mechanisms and finally explore new developments and new applications of different inhibitors.

The chances in the redox priming of nondormant recalcitrant seeds by spermidine.

The problems posed by seed sensitivity to desiccation and aging have motivated the development of various techniques for mitigating their detrimental effects. The redox priming of seeds in antioxidant solution to improve their postharvest performance is one of the approaches. Spermidine (Spd) was tested as an invigorating solution on nondormant recalcitrant (desiccation sensitive) seeds of the silver maple (Acer saccharinum L.). The treatment resulted in an 8-10% increase in germination capacity in seeds subjected to mild and severe desiccation, while in aged seeds stored for six months, no significant change was observed. The cellular redox milieu, genetic stability, mitochondrial structure and function were investigated to provide information about the cellular targets of Spd activity. Spd improved the antioxidative capacity, especially the activity of catalase, and cellular membrane stability, protected genome integrity from oxidative damage and increased the efficiency of mitochondria. However, it also elicited a hydrogen peroxide burst. Therefore, it seems that redox priming in nondormant seeds that are highly sensitive to desiccation, although positively affected desiccated seed performance, may not be a simple solution to reinvigorate stored seeds with a low-efficiency antioxidant system.

A Model for Changes in Germination Synchrony and Its Implements to Study Weed Population Dynamics: A Case Study of Brassicaceae

In every agricultural system, weed seeds can be found in every cubic centimeter of soil. Weed seeds, as a valuable trait underlying the fate of weed populations, exhibit differing levels of seed dormancy, ensuring their survival under uncertain conditions. Seed dormancy is considered as an innate mechanism that constrains germination under suitable conditions that would otherwise stimulate germination of nondormant seeds. This work provides new insight into changes in germination patterns along the dormant to nondormancy continuum in seeds with physiological dormancy. Notable findings are: (1) germination synchrony can act as a new parameter that quantitatively describes dormancy patterns and, subsequently, weed population dynamics, (2) germination synchrony is dynamic, suggesting that the more dormancy decreases, the more synchrony is obtainable, (3) after-ripening and stratification can function as a synchronizing agent that regulates germination behavior. Freshly harvested seeds of Brassica napus with type 3 of non-deep physiological dormancy showed the most synchronous germination, with a value of 3.14, while a lower level of germination asynchrony was found for newly harvested seeds of Sinapis arvensis with type 1 of non-deep physiological dormancy, with an asynchrony value of 2.25. After-ripening and stratification can act as a synchronizing factor through decreasing the asynchrony level and increasing synchrony. There is a firm relationship between seed dormancy cycling and germination synchrony patterns, ensuring their survival and reproductive strategies. By germinating in synchrony, which is accompanied by cycling mechanisms, weeds have more opportunities to persist. The synchrony model used in the present study predicts germination behavior and synchrony along the dormant to nondormancy continuum in weed seeds with physiological dormancy, suggesting a useful method for the quantification of germination strategies and weed population dynamics.

Germination physiology of Cochlospermum fraseri (Bixaceae), a deciduous tree from Northern Australia with physical seed dormancy.

Cochlospermum fraseri ('Kapok', Bixaceae) is a deciduous tree widely distributed throughout semi-arid and monsoon tropical northern Australia, and an important species for ecological restoration in the region. We aimed to better understand the seed biology and ecology of C. fraseri to determine the mechanisms by which seed dormancy might be alleviated, and the conditions that support germination to inform the use of this species in restoration. Dormancy breaking treatments (wet heat, dry heat, scarification) commonly applied to species with physical seed dormancy (PY) were tested along with stratification at 5-35°C (nine treatments). Following dormancy alleviation, seeds were germinated at nine temperatures (5 to 40°C) and five water potentials (0 to -0.8MPa) to understand environmental thresholds that regulate germination physiology in non-dormant seeds. A proportion of seeds (<0.3) lose dormancy naturally in response to warm (25 to 35°C) moist conditions, which dislodges the hypostase plug that prevents water uptake, whilst neither dry (≥100°C) nor wet (~100°C) heat were effective. Dormancy loss was also achieved by exposing seeds to concentrated (95-98% v/v) sulphuric acid for 3-7hours, after which high proportions (>0.75) of germination were observed. Cochlospermum fraseri seeds possess PY, which is alleviated by seasonal temperatures that occur when soil moisture is high, allowing seeds to employ a risk-adverse strategy and maximize establishment success in episodic environments with stochastic rainfall events. The understanding of dormancy alleviation requirements gained here adds to our knowledge of PY worldwide and recruitment dynamics in the Australian monsoonal tropics and will aid land managers and restoration practitioners by informing both seeding sites and optimal time for in situ sowing as well as the potential capacity of this species to form a persistent soil seed bank.

Effect of selected environmental factors on the seed germination of the invasive species Polygala myrtifolia (Polygalaceae) in Australia

Context Polygala myrtifolia L. has become a significant environmental weed in Australia, where it has invaded coastal ecosystems in temperate regions and there is a high risk of extensive further spread. Knowledge of seed-germination behaviour is essential to understand the potential future impact of this species. Aims We investigated the effects of selected environmental factors and dormancy on P. myrtifolia seed germination and emergence to improve management strategies. Methods Seeds were exposed to light, temperature, pH, salinity, osmotic potential and burial depth treatments to assess germination responses, dormancy and viability. Key results Non-dormant seeds readily germinated to high percentages (93.0–95.0%) under specific day–night temperatures of 25°C–15°C regardless of light conditions and across all soil pH (75.0–100.0%). Salinities were tolerated up to 100 mM NaCl (70.0% germination) before sharply declining. Germination reduced from 98.3% to 40.0% at osmotic potentials of −0.4 MPa and −0.6 MPa respectively. Emergence was greatest on the soil surface (48.33%) and absent from depths of 8 cm. Conclusions Germination was high during autumn, winter and spring conditions and across soils of any pH. The species is unlikely to invade areas of high salinity; however, it is moderately tolerant of low soil moisture during germination. Implications There is high risk of P. myrtifolia further invading sensitive ecosystems because of its high germination success. Preventing seed dispersal and ensuring seedlings are controlled on emergence are critical to reducing its impact. We recommend that the cultivation and sale of this species should be prohibited across Australia to prevent further spread.

Domestication of azuki bean and soybean in Japan: From the insight of archeological and molecular evidence.

Domestication of azuki bean and soybean has enabled them to acquire non-dormant seeds, non-shattering pods, and larger seed size. Seed remains of the Jomon period recently discovered at archeological sites in the Central Highlands of Japan (6,000-4,000 BP) suggest that the use of azuki bean and soybean and their increase in seed size began earlier in Japan than in China and Korea; molecular phylogenetic studies indicate that azuki bean and soybean originated in Japan. Recent identification of domestication genes indicate that the domestication traits of azuki bean and soybean were established by different mechanisms. Analyses of domestication related genes using DNA extracted from the seed remains would reveal further details about their domestication processes.

RNA-seq study reveals the signaling and carbohydrate metabolism regulators involved in dormancy release by warm stratification in Paris polyphylla var. yunnanensis.

Long-term seed dormancy of Paris polyphylla var. yunnanensis limits its large-scale artificial cultivation. It is crucial to understand the regulatory genes involving in dormancy release for artificial cultivation in this species. In this study, seed dormancy of Paris polyphylla var. yunnanensis was effectively released by warm stratification (20°C) for 90 days. The freshly harvested seeds (dormant) and stratified seeds (non-dormant) were used to sequence, and approximately 147 million clean reads and 28,083 annotated unigenes were detected. In which, a total of 10,937 differentially expressed genes (DEGs) were identified between dormant and non-dormant seeds. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) classification revealed that the majority unigenes involved in signaling transduction and carbohydrate metabolism. Of them, the signaling transduction-related DEGs were mainly hormones-, reactive oxygen species (ROS)-, and transcription factor (TF)-related genes. The largest number of signaling transduction-related DEGs were auxin-responsive genes (SAUR, AUX/IAA, and ARF) and AP2-like ethylene-responsive transcription factor (ERF/AP2). Moreover, at least 29 DEGs such as α-amylase (AMY), β-glucosidase (Bglb/Bglu/Bglx), and endoglucanase (Glu) were identified involving in carbohydrate metabolism. These identified genes provide a valuable resource to investigate the molecular basis of dormancy release in Paris polyphylla var. yunnanensis.

Seed ecology of post-fire flowering species from the Cerrado

AbstractPost-fire flowering (PFF) species resprout, flower and disperse seeds within weeks after fire. This may be an important strategy to recruit new individuals and colonize the gaps opened by fire. The seeds released in the post-fire environment may interact with byproducts derived from plant burning, and the resulting ash may have compounds that can promote the germination of various seeds, particularly those with permeable coats. In the Cerrado ecoregion, PFF is a strategy commonly observed in the species of the ground layer, but their seeds are rarely investigated. So, we examined the quality and the germination of the seeds of 13 species that disperse seeds within 3 months after fire. We estimated the amount of empty, filled and predated seeds for each species, and tested the germination with or without ash. There was a clear separation in seed quality as dicots produced 35–75% filled seeds but grasses &lt;15%. Pre-dispersal predation was only observed for dicots (&lt;10%). Ash stimulated the germination of two out of the three dormant species but inhibited the germination of three non-dormant species. Overall, the seeds produced in response to fire are an important source of genetic variability in an ecosystem that has resprouting as the main persistence strategy. As most species have non-dormant seeds, ash may only be important to stimulate the germination of few PFF species. Even so, ash can be completely washed away by rains before seeds are dispersed and may not have an effect under field conditions.

LARGER SEED MASS PREDICTS HIGHER GERMINATION AND EMERGENCE RATES IN SANDY GRASSLAND SPECIES WITH NON-DORMANT SEEDS

The lack of knowledge on the traits related to the germination and establishment of native plant species represents obstacles to restoration. Seed mass, germination and emergence variability from two characteristic grasses (Festuca vaginata and Stipa borysthenica), and two dicots (Centaurea arenaria and Dianthus serotinus) of Hungarian sandy grasslands from altogether 34 localities were tested. Our results showed that seed mass had a significant positive effect on germinability of the dicots and on seedling emergence of all species. The laboratory germination capacity of S. borysthenica was low due to dormancy. We found a significant variability among seed traits and emergence between localities in all the species except for the germination of S. borysthenica. This significant variation among populations might be explained by local adaptation or maternal effects. We conclude that germination under laboratory-regulated conditions is a good predictor of seedling emergence for restoration projects, but limited to species with non-dormant seeds.

Type 2 Nondeep Physiological Dormancy in Seeds of Fraxinus chinensis subsp. rhynchophylla (Hance) A.E.Murray

Fraxinus chinensis subsp. rhynchophylla (Oleaceae), hereafter F. rhynchophylla, is an important timber species in northeast China; however, little is known about its seed dormancy and germination, which hinders regeneration of the species from seeds for reforestation and conservation. Our aim was to determine the class of seed dormancy and how to break it. Studies were conducted to determine the permeability of the seed coat to water, changes in embryo development during cold stratification and effects of cold stratification on germination over a range of temperatures. The seeds were water-permeable, and the embryo was fully developed and filled the embryonic cavity. Cold stratification at 5 °C for 8 weeks was effective in breaking dormancy; thus, we conclude that the seeds have nondeep physiological dormancy (PD). As cold stratification time was increased, the ability of seeds to germinate at low temperatures (e.g., 10 °C and 15 °C) increased, indicating the presence of Type 2 nondeep PD, in which the minimum temperature for germination decreases during dormancy-break. Nondormant seeds germinated to high percentages and rates at constant temperatures of 25 °C (germination percentage was 63%) and at alternating temperature regimes of 35 °C/25 °C, 30 °C/15 °C, 25 °C/20 °C and 20 °C/10 °C (germination percentage was 66%, 67%, 65% and 66%, respectively). To produce seedlings, we recommend 8 weeks of cold stratification at 5 °C before sowing the seeds at temperatures ranging from 15 °C to 30 °C.