Non-deep Simple Morphophysiological Dormancy Research Articles

Conservation implications of seed germination studies of Aquilegia fragrans Benth.: A native and endangered medicinal plant species of Kashmir Himalaya

Insufficient investigation of seed germination studies of threatened plant species creates practical obstacles to their conservation efforts. Here, we investigate the seed germination of Aquilegia fragrans Benth.-an endangered medicinal plant species native to Himalaya. The effects of stratification conditions including time (10, 20, 30, and 40 days), temperature (−4, −10, and −20 °C), and hormone treatments (250 ppm GA3, 30 ppm BAP, and 30 ppm Zeatin) on germination of A. fragrans seeds collected from the alpine belt of Kashmir Himalaya were examined. Seeds of species exhibited non-deep simple morphophysiological dormancy (MPD). Seed germination showed significant differences among the various treatments. It was observed that the application of GA3, zeatin, and BAP significantly improved seed germination as compared with the control. The highest germination percentage (73 ± 1 %) along with maximum germination index (1.05 ± 0.05) was recorded in T30 (Seeds stratified for 30 days at −10 °C and treatment with Zeatin 30 ppm) followed by T19 (seeds stratified at −10 °C for 20 days and treatment with zeatin 30 ppm). The seed germination studies of A. fragrans have not been carried out before, and the information gathered in the present study may prove useful for the conservation of the target plant species. The present study will help in the conservation, sustainable development, and restoration of this prized medicinal plant species.

Seed Dormancy and Germination Requirements of Torilis scabra (Apiaceae)

The timing of seed germination significantly affects the fitness and life cycle of plants. Torilis scabra is a perennial medicinal herb occurring in mixed forests but the increasing use and modification of forestlands in recent decades has led to the degeneration of its natural habitat. Nonetheless, the requirements for germination in T. scabra remain unclear. The present study focused on identifying conditions necessary to break T. scabra seed dormancy and describing its seed dormancy type. By periodically collecting seeds that were sown in the field, germination phenology was studied. The impact of light, temperature, and warm/cold stratification on breaking seed dormancy and promoting germination was also determined through incubating seeds in laboratory conditions. Additionally, the effect of GA3 was explored to more accurately identify the type of dormancy present. The results demonstrated that the seeds of T. scabra possessed small, undeveloped embryos with physiological dormancy at the time of maturity. In the field, embryo growth initiated in early spring and the embryo–seed length ratio increased by ~300% before the radical emerged. In the laboratory, the embryo–seed length ratio increased from 0.24 to 0.82 when seeds were subjected to cold stratification at 4 °C and then transferred to 15/25 °C. Germination was observed across a broad temperature range after cold stratification. GA3 also helped to break dormancy but after-ripening did not. Taken together, the results suggest that seeds of T. scabra have non-deep simple morphophysiological dormancy.

Non-deep simple and deep simple morphophysiological dormancy in seeds of three species of Ilex from subtropical and tropical regions of Taiwan

AbstractDormancy-breaking requirements and level of morphophysiological dormancy (MPD) were determined for seeds of Ilex formosana and I. uraiensis from the subtropical region, and seeds of I. rotunda from both the subtropical and tropical regions of Taiwan. We hypothesized that some Ilex species would have deep simple MPD broken by warm stratification. Germination of seeds and embryo growth was monitored at 30/20, 25/15, 20/10, 15/5°C and at 25°C. Seeds were cold-stratified and then incubated at 25/15°C, and seeds treated with GA3 and GA4 were incubated at 25/15°C. Fresh seeds reached 50% germination after 11–45 weeks of warm stratification. Pre-treatment with GA increased germination percentages of I. formosana and I. rotunda (tropical) but not I. uraiensis and I. rotunda (subtropical), while cold stratification did not promote germination of either species but increased the germination rate of I. rotunda (tropical). Embryo length in seeds of all species increased ≥710% prior to root emergence, and growth occurred during warm stratification. The positive response to GA and relatively short time for beginning of germination and to reach 50% germination indicate non-deep simple MPD in seeds of I. formosana and I. rotunda (tropical). The negative response to GA and long time for beginning of germination and to reach 50% germination indicate deep simple MPD in seeds of I. uraiensis and I. rotunda (subtropical). Thus, in both the subtropical and tropical regions of Taiwan, the seeds of Ilex species have non-deep simple and deep simple MPD that are broken by warm stratification. Furthermore, GA treatment increases the germination rate and percentage of Ilex seeds with non-deep simple MPD, and cold stratification promotes the seed germination rate of Ilex species with non-deep simple MPD in tropical region.

Embryo maturation, dormancy and seed storage behaviour of Gymnacranthera canarica (King) Warb., a threatened endemic tree species of Southern Western Ghats

Gymnacranthera canarica is a severely endangered endemic tree species found in the Myristica swamps of the Southern Western Ghats. Seed storage behaviour is an essential factor to consider when developing effective conservation methods for plant genetic resources whose ex-situ preservation is unclear. The seed storage behaviour, seed dormancy state, dormancy breaking treatments, germination, and phytohormonal analysis of G. canarica were explored in this work. G. canarica seed moisture at shedding was 28.86%, germinated to 34% at 25ºC, and had a low germination rate in natural conditions. Germination was considerably aided by Gibberellic acid pretreatment and drying stratification. G. canarica seeds may have non-deep simple morphophysiological dormancy, as evidenced by the fact that their embryos grew at temperatures between 20 and 25ºC (MPD). Seeds can be stored for up to 60 days at 20ºC after being desiccated to 19.37% suggest that G. canarica seeds are recalcitrant, with non-deep simple morphophysiological dormancy, and that seed pretreatment with Gibberellic acid prior to germination could be a viable approach for mass propagation and long term ex-situ conservation could be the potential storage of this critically endangered species.

Seed germination ecology of common bladderwort (Utricularia vulgaris L.)

Generative reproduction of the carnivorous aquatic plant Utricularia vulgaris (Lentibulariaceae) from seeds may be a critical process in the recovery of natural populations following temporary drying of habitat, and in the colonisation of new potential sites through dispersal of seeds by water birds. However, little is presently known about the seed ecology and germination biology of this species. We tested the germination response of seeds under various temperature and seed storage regimes, to examine the processes required for seed dormancy alleviation and the effects of different germination solution and temperature on germination probability. Seeds likely possess non-deep simple morphophysiological dormancy alleviated by warm stratification. Highest germination success was recorded for warm-stratified seeds and seeds exposed to ethylene. Seeds were photophilous, with germination more successful at 21 °C than at 25 °C and greatest in slightly alkaline (pH 8) germination solution containing KHCO3, CaCl2 and MgSO4 mimicking the mesotrophic humic waters in which the species naturally occurs. In the alkaline solution, 97 % of seeds rose to the surface prior to germination. In natural habitats, this effect may facilitate seedlings reaching the warmer and irradiated water surface. As seed germination success appears linked to light availability, water chemistry, and seed position in the water column, careful management and ecological restoration of remnant habitats harbouring this species may need to ensure positive conservation outcomes.

Non-Deep Simple Morphophysiological Dormancy and Germination Characteristics of Gentiana triflora var. japonica (Kusn.) H. Hara (Gentianaceae), a Rare Perennial Herb in Korea

This study investigated the kind of seed dormancy and seed germination of Gentiana triflora var. japonica (Kusn.) H. Hara for developing a seed propagation method. The seeds were collected in October 2020 from plants at Mt. Sobaeksan, Korea. In a water imbibition experiment, seed weights increased by >101.9% of their initial masses over 12 h. Effects of incubation temperature (5, 15, 20, 25, 15/6, or 25/15 °C), cold stratification period (5 °C; 0, 4, 8, or 12 weeks), and gibberellic acid (GA3; 0, 10, 100, or 1000 mg∙L−1) and potassium nitrate treatment (KNO3; 0, 1000, 2000, or 4000 mg∙L−1) on seed germination were investigated to characterize seed dormancy. These seeds exhibited underdeveloped embryos during seed dispersal. The seeds failed to reach the final germination of 15.0% after treatment at 5, 15, 20, 25, 15/6, or 25/15 °C. After cold stratification for 8 weeks, the germination increased dramatically by >90.0% compared to that at 0 weeks. After the GA3 treatment, the germination reached >80.0% within 5 days. The final germination was 90.0% in the 100 mg∙L−1 GA3 treatment group. However, the KNO3 treatment had no effect on seed germination. Therefore, the G. triflora var. japonica seeds exhibited non-deep simple morphophysiological dormancy.

Seed dormancy, germination and storage behavior of Magnolia sinica, a plant species with extremely small populations of Magnoliaceae

Magnolia sinica is one of the most endangered Magnoliaceae species in China. Seed biology information concerning its long-term ex situ conservation and utilization is insufficient. This study investigated dormancy status, germination requirements and storage behavior of M. sinica. Freshly matured seeds germinated to ca. 86.5% at 25/15 °C but poorly at 30 °C; GA3 and moist chilling promoted germination significantly at 20 °C. Embryos grew at temperatures (alternating or constant) between 20 °C and 25 °C, but not at 5 °C or 30 °C. Our results indicate that M. sinica seeds possibly have non-deep simple morphophysiological dormancy (MPD). Seeds survived desiccation to 9.27% and 4.85% moisture content (MC) as well as a further 6-month storage at −20 °C and in liquid nitrogen, including recovery in vitro as excised embryos. The established protocol ensured that at least 58% of seedlings were obtained after both cold storage and cryopreservation. These results indicate that both conventional seed banking and cryopreservation have potential as long-term ex situ conservation methods, although further optimized approaches are recommended for this critically endangered magnolia species.

Dormancy cycles in Aquilegia oxysepala Trautv. et Mey. (Ranunculaceae), a species with non-deep simple morphophysiological dormancy

Seed dormancy and the formation of a soil seed bank is important plant regeneration strategies, especially if the environment is unpredictable. The present research explores how environmental factors control seed dormancy release, and how seed dormancy is related to the soil seed bank and regeneration of the perennial Aquilegia oxysepala. The effects of incubation temperature, light, cold and warm stratification, gibberellic acid (GA3) along with the germination phenology of A. oxysepala in the field were used to determine the type of seed dormancy. Seasonal change of seed dormancy was determined by regularly exhuming buried seeds and incubating them in laboratory conditions. A. oxysepala seeds has underdeveloped (small) embryos along with physiological dormancy at dispersal. With the increased amounts of cold stratification, the germination of A. oxysepala increased gradually. GA3 served as a substitute for cold stratification. Breaking of physiological dormancy under natural temperatures in the field occurred in winter, while growth of embryos and germination of seeds occurred in early spring. Viable seeds that had not germinated in early spring were induced into secondary dormancy by high soil temperatures. A. oxysepala provides one of a few examples of dormancy cycling in seeds with morphophysiological dormancy. Freshly matured seeds of A. oxysepala seeds have non-deep simple morphophysiological dormancy. The annual dormancy–non-dormancy cycle maintains the coordination between timing of seedling emergence with favorable seasons, thus increasing the survival chances of seedlings in environments with seasonal changes.

Dormancy-breaking and germination requirements of Thalictrum squarrosum Stephan ex Willd. seeds with underdeveloped embryos

The timing of seed germination has a significant effect on the life cycles and fitness of plants. Thalictrum squarrosum is a perennial herb with medical and ornamental value. However, the dormancy type and the regeneration strategy it uses to adapt to the natural habitat have yet to be investigated. The present study determined the seed germination requirements of T. squarrosum seeds and characterized the type of seed dormancy observed in this species. The results indicate that seeds of T. squarrosum had differentiated but underdeveloped embryos. After 30 days of incubation under 5/15, 10/20, 15/25, and 20/30 °C in light/dark conditions, no seed germination was observed, which indicated that the seeds had a morphophysiological type of dormancy. After 12 weeks of cold stratification, > 90 % seeds germinated at 5/15 and 10/20 °C. In addition, a gibberellic acid (GA3) treatment can substitute for the need for cold stratification and successfully broke dormancy in T. squarrosum seed. Seeds treated with 1000 mg/L GA3 had higher germination rates than those treated with 10 or 100 mg/L GA3. Embryo growth and germination began in February under natural conditions of the year following production. We conclude that T. squarrosum seed exhibits non-deep simple morphophysiological dormancy. These findings will enhance our understanding of the regeneration strategy of T. squarrosum that allows it to adapt to the environment and will offer a reference to horticulturalists and seed ecologists in understanding the germination processes of T. squarrosum.

Different levels of morphophysiological seed dormancy in Ribes alpinum and R. uva-crispa (Grossulariaceae) facilitate adaptation to differentiated habitats

Aim of the study: To study the germination ecology of two species of the genus Ribes to reveal their levels of morphophysiological dormancy (MPD) and to facilitate the production of plants from seeds, a key tool for population reinforcement.Area of study: Experiments were carried out both outdoors and in the laboratory in Albacete (Spain) with seeds from the Meridional Iberian System mountain range.Material and methods: Seeds from one population of Ribes alpinum and from other of Ribes uva-crispa were collected during several years. Embryo length, radicle and seedling emergence, and effects on germination of stratification and GA3 were analysed to determine the level of MPD.Main results: In R. alpinum, embryo length in fresh seeds was 0.49 mm, needing to grow to 1.30 mm to germinate. Warm stratification (25/10ºC) promoted embryo length enlargement to 0.97 mm. Afterwards, seeds germinated within a wide temperature range. Embryo growth and seedling emergence occur late summer-early autumn. In R. uva-crispa, embryo length in fresh seeds was 0.52 mm, being 2.10 mm the minimal size to germinate. Embryos exposed to a moderately warm stratification (20/7ºC + 15/4ºC) followed by cold (5ºC) grew to 2.30 mm. Then, seeds germinated ≥ 80% when incubated at temperatures ≥ 15/4ºC. Embryos grew in autumn/early winter, and seedlings emerged late winter-early spring.Research highlights: These results showed that R. alpinum seeds have a nondeep simple MPD while R. uva-crispa seeds have a nondeep complex MPD. Moreover, the different germinative models found for each species help explain their installation in distinct habitats.Keywords: Ribes; seed dormancy break; radicle emergence; seedling emergence; nondeep simple and nondeep complex MPD.Abbreviations used: Morphophysiological dormancy (MPD), morphological dormancy (MD), Gibberellic acid (GA3), months (m).

Seed dormancy in Campanulaceae: morphological and morphophysiological dormancy in six species of Hawaiian lobelioids

We determined the requirements for dormancy break/germination and kind of dormancy in seeds of the Hawaiian lobelioids Cyanea kunthiana, Delissea rhytidoperma, Lobelia grayana, L. hypoleuca, Trematolobelia grandifolia, and T. singularis. Fresh seeds were incubated in light/dark at 15/6, 20/10, and 25/15 °C, and germination monitored at two-week intervals for 14 weeks. For each species, the mean embryo length (E): seed (S) length ratio was determined for freshly matured seeds and for seeds at the time the seed coat split but before radicle emergence (germination). The embryo in seeds of all six species incubated at 25/15 °C grew inside the seed prior to germination (42%–148% increase in E:S ratio, depending on species). Seeds of L. grayana and L. hypoleuca have morphological dormancy (MD); they germinated to 82%–98% at the three temperature regimes in 4 weeks. Seeds of the other species have nondeep simple morphophysiological dormancy (MPD) and require >4 weeks for maximum germination to occur. Our results add to the growing body of knowledge about the kind (class) of seed dormancy in Campanulaceae, which suggests that seeds of members of this family have either MD or MPD and embryos grow at warm (≥15 °C) temperatures.

Non-deep simple morphophysiological dormancy in seeds of Angelica keiskei (Apiaceae)

Angelica keiskei is a vegetable and medicinal plant with high economic value. Growing demands for market and unprecedented anthropogenic damage to forests has caused severe degeneration of its populations. Moreover, the germination protocol for seeds of A. keiskei is complex, leading to a high cost of propagation and seed wastage. The primary aim of present study was to determine the requirements for seed dormancy break and germination and to characterize the class of seed dormancy in A. keiskei. The effects of temperature, light, cold stratification, dry storage, gibberellic acid (GA3) on dormancy break and germination were tested combined with move-along experiments and a germination phenology study. The results showed that seeds of A. keiskei had embryos that were differentiated but underdeveloped (small) and had physiological dormancy (PD) at maturity in autumn. Before the emergence of radicles, the embryo/seed length ratio increased from 0.20 to 0.85, a 425% increase. Germination of A. keiskei gradually increased following increased amounts of cold stratification. After 8 weeks of cold stratification, seeds germinated to 75, 78, 63 and 14% at 5/15, 10/20, 15/25 and 20/30 °C, respectively, in light. GA3 substituted for cold stratification. After 8 weeks of cold stratification, > 80% of seeds treated with ≥10 mg·L-1 GA3 germinated across the temperature range. In the move-along experiments, little or no embryo growth and germination occurred at 5 °C. However, after breaking PD by cold stratification at 5 °C, the rate of embryo growth increased rapidly at warm temperatures (5/15 °C) and reached the critical length for germination within 2 weeks of incubation. We identified that seeds of A. keiskei exhibited non-deep simple morphophysiological dormancy. Natural cold stratification broke PD during winter and allowed the germination of seeds and the production of seedlings at the start of the growing season.

Germination of Aristolochia Seeds (Aristolochiaceae)

We studied the seed morphology and germination of 17 Aristolochia species (A. arborea, A. baetica, A. inflata, A. gigantea, A. gracilis, A. clematitis, A. contorta, A. fimbriata, A. labiata, A. littoralis, A. macrophylla, A. manshuriensis, A. maxima, A. rotunda, A. sempervirens, A. tomentosa, A. trilobata). The seeds of A. clematitis, A. contorta, A. trilobata, A. labiata, and A. maxima, as well as all species of Siphisia section (seeds with no wings), have the higher seed morphometric parameters. The seed weight characteristics of species typical of tropical climatic zones (the Gymnolobus section) were lower by ten or more times than those of the species of the other two sections, which are typical of a temperate climate. The greater weight of seeds studied for the species of Siphisia and Diplolobus sections is associated with the presence of a voluminous endosperm, which is required for the embryo development after a long period of time between dissemination and seedlings emergence. The period from sowing to the beginning of germination and the length of the germination period differ between species; the duration of germination is from 1 month to 3.5 years. The seeds of the species from temperate climatic zones (sections Diplolobus and Siphisia) have a non-deep simple morphophysiological dormancy, and the germination starts 1–11 months after seed sowing. We observed intervals in germination from 2 to 12 months in the species of the Diplolobus section; after the intervals, the germination process was continued. The seeds of most of the Gymnolobus section species from tropical zones have a morphological type of dormancy and germinate without intervals. The prolonged germination period and the type of morphophysiological dormancy of seeds have an adaptive value for the species conservation and survival in situ and ex situ.

Three levels of simple morphophysiological dormancy in seeds ofIlex(Aquifoliaceae) species from Argentina

AbstractAs a contribution to understanding the world biogeography of seed dormancy in the cosmopolitan genusIlex, we studied seeds ofI.argentina,I. brasiliensis,I. brevicuspis,I. dumosa,I. paraguariensisandI. theezansfrom the subtropical region of Argentina. We hypothesized that seeds of these species have non-deep simple morphophysiological dormancy (MPD). Effects of temperature, cold stratification and gibberellic acid (GA3) on seed germination and embryo growth were tested. Regardless of incubation temperature, little or no germination occurred for any species until ≥6 weeks. There was an up to 3-fold increase in embryo length to seed length (E:S) ratio before seeds germinated, and embryos grew only during warm-stratifying conditions. Seeds ofI. brasiliensis,I. brevicuspisandI. theezanshad non-deep simple MPD and germinated to ≥80% after 12, 24 and 16 weeks, respectively. Cold stratification increased germination ofI. brasiliensisandI. brevicuspis, and GA3increased the rate but not final germination percentage ofI. brasiliensisandI. theezans. Fresh seeds ofI. dumosarequired 40 weeks of warm stratification to germinate to 53%, while those after-ripened for 2 months germinated to 81% after 30 weeks; this species has intermediate simple MPD. Seeds ofI. argentinaandI. paraguariensisgerminated to 15 and 21%, respectively, after 40 weeks of warm stratification and did not after-ripen or respond to GA3; these seeds have deep simple MPD. This is the first report of intermediate and deep simple MPD that is broken by warm stratification, thereby increasing our knowledge of seed dormancy inIlexand in subtropical regions.

Morphophysiological dormancy, germination, and cryopreservation in Aristolochia contorta seeds

Background and aims – Aristolochia contorta is a valuable medicinal plant, a relict of the Tertiary flora. Little is known about the germination biology of Aristolochia. The specific objectives of the present study were to (1) determine the type of dormancy in seeds of A. contorta, (2) describe the embryo development, and (3) explore the influence of deep freezing of the seeds in liquid nitrogen on their germinability.Methods – Seeds were germinated in Petri dishes in sand previously sterilised at high temperature; germination experiments were carried out at 27±2°C under natural light. All measurements of seeds and embryos were done using light microscopy (LM). For cryopreservation, fresh seeds were placed in aluminium foil bags, immersed into liquid nitrogen (-196°С), and stored for twelve months.Key results – The seeds of Aristolochia contorta have non-deep simple morphophysiological dormancy. A variety of embryo forms were revealed for Aristolochia species for the first time. Two cases of polyembryony were noted in A. contorta. The seeds of A. contorta are resistant to cryopreservation in liquid nitrogen.Conclusions – High variability in dormancy depth and the extended germination period of A. contorta seeds can be considered as adaptive strategies for survival in unfavourable conditions and renewal of germination under optimal conditions. Cryopreservation helped maintain the viability of A. contorta seeds but did not lead to the breaking of the dormancy; hence, for successful germination, it is necessary to use methods of breaking dormancy after freezing.

Morphophysiological seed dormancy inHeptacodium

AbstractHeptacodium miconiodesis an endangered, monotypic genus in the Caprifoliaceae endemic to China. Species within the Caprifoliaceae have been shown to have morphological or morphophysiological dormancy.Heptacodiumseeds had an underdeveloped embryo at the time of fruit dispersal with an embryo that occupied approximately 12% of the seed length. Cold (8 weeks at 5°C) and warm (8 weeks at 20°C) stratification was effective for dormancy release, but embryo growth prior to germination only occurred at warm temperatures (20°C). Gibberellic acid treatment partially substituted for cold stratification. Final seed germination percentage was not different after warm or cold stratification; however, seeds initially exposed to cold stratification germinated faster and more uniformly. Cold stratified seeds reached 50% final germination approximately 55 days sooner than warm stratified seeds. Prior to radicle emergence, embryos grew to fill approximately 60% of the seed through an endosperm channel that occupied the centre portion of the endosperm. Cells in the endosperm channel had thinner cell walls and fewer storage vesicles compared with other endosperm cells. Channel cells formed a dissolution zone ahead of embryo elongation assumed to be involved with enzymatic hydrolysis of storage reserves. Based on these results, it was concluded thatHeptacodiumdisplays the characteristics of seeds with non-deep simple morphophysiological dormancy.

Dormancy breaking and germination requirements of seeds of Thalictrum uchiyamae (Ranunculaceae) with underdeveloped embryos

Abstract Thalictrum uchiyamae Nakai is an herbaceous perennial plant that has potential for greater utilization for landscaping and medicinal purposes. In the present study, we investigated some of the factors that affect seed dormancy and germination in this species. To determine the temperature requirements for embryo growth and germination in field conditions, the seeds were buried in field soil. Every 1 or 2 weeks, the seeds were exhumed, and embryo growth, germination, and seedling emergence were investigated. In the laboratory, the effects of temperature and GA3 on dormancy break and germination were investigated in order to characterize the seed dormancy. The seeds had underdeveloped embryos that were physiologically dormant at maturity in late September. In natural conditions, embryo growth and germination occurred in March of the following year, and seedlings emerged in early April. The physiological dormancy of the embryos was broken by cold stratification at 5 °C for 8 weeks, but warm temperatures (25/15 °C) were required to promote embryo elongation even after the physiological dormancy was broken. GA3 treatment could substitute for the cold stratification requirements and broke seed dormancy of T. uchiyamae, 87.3% of which germinated after 8 weeks of incubation at 25/15 °C at 100 mg ⋅L−1 GA3 soaking treatment. These results suggest that the seeds of T. uchiyamae exist in a state of non-deep simple morphophysiological dormancy. The temperature requirements for the dormancy break of the seeds enabled the seedlings to emerge in the very beginning of the growing season the following year. These results represent practical knowledge for propagation of these plants from seed.

The morphophysiological dormancy in Amborella trichopoda seeds is a pleisiomorphic trait in angiosperms.

Recent parsimony-based reconstructions suggest that seeds of early angiosperms had either morphophysiological or physiological dormancy, with the former considered as more probable. The aim of this study was to determine the class of seed dormancy present in Amborella trichopoda , the sole living representative of the most basal angiosperm lineage Amborellales, with a view to resolving fully the class of dormancy present at the base of the angiosperm clade. Drupes of A. trichopoda without fleshy parts were germinated and dissected to observe their structure and embryo growth. Pre-treatments including acid scarification, gibberellin treatment and seed excision were tested to determine their influence on dormancy breakage and germination. Character-state mapping by maximum parsimony, incorporating data from the present work and published sources, was then used to determine the likely class of dormancy present in early angiosperms. Germination in A. trichopoda requires a warm stratification period of at least approx. 90 d, which is followed by endosperm swelling, causing the water-permeable pericarp-mesocarp envelope to split open. The embryo then grows rapidly within the seed, to radicle emergence some 17 d later and cotyledon emergence after an additional 24 d. Gibberellin treatment, acid scarification and excision of seeds from the surrounding drupe tissues all promoted germination by shortening the initial phase of dormancy, prior to embryo growth. Seeds of A. trichopoda have non-deep simple morphophysiological dormancy, in which mechanical resistance of the pericarp-mesocarp envelope plays a key role in the initial physiological phase. Maximum parsimony analyses, including data obtained in the present work, indicate that morphophysiological dormancy is likely to be a pleisiomorphic trait in flowering plants. The significance of this conclusion for studies of early angiosperm evolution is discussed.

Non-deep simple morphophysiological dormancy in seeds of heavenly bamboo (Nandina domestica Thunb.)

Heavenly bamboo (Nandina domestica) is a popular ornamental shrub used as an indoor plant and for landscaping. However, seed propagation has been limited due to its very slow germination (9 months under natural conditions) caused by an extended seed dormancy period. We used various temperature treatments, including simulations of seasonal temperature changes, to investigate the temperature requirements for dormancy breaking and the germination of heavenly bamboo seeds at the embryo and whole-seed levels. Heavenly bamboo seeds were found to have no physical dormancy because the seeds imbibed water readily. However, its mature seeds contained underdeveloped embryos (E:S ratio <0.2) that had morphological dormancy. The seeds did not germinate within a month of incubation at fluctuating temperatures of 25/15, 20/10, and 15/6, or at 5°C alone, which indicated that they had morphophysiological dormancy as well as morphological dormancy. A simulation study of seasonal temperatures (move-along test) showed that warm stratification (25/15°C) was needed to stimulate embryo growth and germinate the seeds, but cold stratification (5°C) was not required. Warm stratification at a constant 20°C hastened seed germination more than a fluctuating temperature at 25/15°C, and it led to a germination time that was shorter by 4 months than that under natural conditions. Application of gibberellic acid (GA3) at 100 and 1000mgL−1 could substitute for warm stratification and broke dormancy in seeds incubated at 15/6°C. These results suggested that heavenly bamboo seeds had non-deep simple morphophysiological dormancy, which could be broken by warm stratification at 25/15 or 20°C.

Non-deep simple morphophysiological dormancy in seeds of the rare Alpinia galanga: a first report for Zingiberaceae

AbstractLittle information is available on seed dormancy of members of the Zingiberales and especially the Zingiberaceae. Our aim was to investigate the dormancy breaking and germination requirements of Alpinia galanga in vitro with a minimum number of seeds, using the move-along experiment. The mass of imbibed seeds increased by 17.5% in 1 d, showing that seeds were water permeable. The best germination in the move-along experiment (86.7%) was obtained when seeds were exposed to the sequence of temperature regimes that began with winter (20/10°C), and seeds began to germinate after 6 weeks at this temperature regime. Seeds dry stored for 4 months and then incubated at the sequence of temperature regimes that began with summer (30/20°C) started germinating in the sixth week at this temperature regime and had germinated to 93.3% after 18 weeks. Seeds kept dry for 4 months and then treated with 50 mg l−1 gibberellic acid (GA3) began to germinate at 30/20°C after 2 weeks. Control seeds incubated continuously at 20/10, 25/15 or 30/20°C germinated to 80.6, 77.8 and 60.0%, respectively. When incubated at 15, 20, 25 or 30°C, the ideal temperature for embryo growth was 20°C. Since GA3 and dry storage can break non-deep physiological dormancy and embryos grew during warm stratification, seeds of A. galanga have non-deep simple morphophysiological dormancy (MPD). This is the first report of non-deep simple MPD in the Zingiberaceae.