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EFP received financial support from the Regional Government of Asturias and the FP7 – Marie Curie – COFUND programme of the European Commission (Grant ‘Clarín’ ACB17-19). BJ-A and EFP were funded by the Spanish Research Agency (PID2019-108636GA/AEI/10.13039/501100011033) (...)

The genus Paeonia (Paeoniaceae) includes many popular ornamentals, has colorful flowers and contains several Chinese medicinal species. The germination protocol for seeds of Paeonia species is complex and impedes the breeding of new cultivars and contributes to the rarity and high cost of the plants. Although numerous reports on seed dormancy/germination in peonies are scattered throughout the literature, most of them are in Chinese. The primary aims of this paper are to provide a general overview of the available information on seed dormancy/germination in peonies and to make some suggestions regarding propagation for the peony industry and breeders. Most Paeonia species have epicotyl dormancy. The embryo is differentiated into organs, but it is underdeveloped (small) and must grow inside the seed before the radicle can emerge. Germination of peony seeds requires warm stratification for embryo growth and radicle protrusion followed by cold stratification for epicotyl growth. In addition, the epicotyl is sensitive to cold stratification only after the root has grown to a certain length. GA₃ treatment enhances embryo growth and subsequent germination percentages. Further investigations on the physiology, genetics and proteomics would contribute to a better understanding of seed dormancy in Paeonia.

Although mature seeds of the monogeneric conifer family Cephalotaxaceae sensu stricto have underdeveloped embryos, no definitive studies have been done to classify dormancy in this family. Our primary purpose was to determine the kind of dormancy in seeds of Cephalotaxus wilsoniana and to put the results into a broad phylogenetic context for gymnosperms. The species is of horticultural and medicinal value, and information is needed on how to propagate it efficiently from seeds. Embryo growth and germination were monitored for seeds at warm, cold and warm plus cold temperatures, and germination was monitored for seeds subjected to: (1) cold →  warm →  cold →  warm; and (2) warm →  cold →  warm →  cold →  warm temperature sequences. The effects of gibberellic acids GA3 and GA4 were tested on radicle emergence in ungerminated seeds and on shoot emergence in root-emerged seeds. Germination was promoted by ≥ 36 weeks of warm stratification followed by ≥ 8 weeks of cold stratification, but only if seeds were returned to high temperatures. The underdeveloped embryo must increase in length by >120% before the radicle emerges. Neither GA3 nor GA4 was effective in promoting radicle emergence; however, both plant growth regulators increased rate (but not percentage) of shoot emergence in root-emerged seeds. We conclude that seeds of C. wilsoniana have the deep simple level of morphophysiological dormancy (MPD), C1b-C3-B1b; thus, warm stratification followed by cold stratification and then warm-temperature incubation are required for germination. In gymnosperms, MPD is known in cycads, Ginkgo and now in three families of conifers.

Seed germination is critical to the life history of plants, playing an important role in the successful recruitment, colonization, and even invasion of new individuals within and outside population distribution ranges. Cold stratification and temperature are the key factors affecting seed germination traits. Studying how these two factors drive geographical variation in seed germination is essential to analyze and predict the geographical distribution range of alien plants in novel habitats. Spartina alterniflora , native to the United States, was introduced into China in 1979 and has spread over 20° of latitude along the eastern coast of China. Germination plays a crucial role in S. alterniflora ’s large-scale invasion and diffusion across latitude. To evaluate the effects of cold stratification and temperature on seed germination of S. alterniflora across latitude, we collected seeds at seven locations across latitude in China. We exposed these provenances to cold stratification at 4°C (0, 1, 3, and 5 months) and germination temperature (5°C, 15°C, 25°C, and 35°C) treatments in growth chambers. Seed germination was observed for 98 days, and we calculated germination rate, germination index, and germination time. Results indicated that longer cold stratification significantly promoted germination rate and germination index, but decreased germination time. Similarly, higher germination temperature significantly promoted germination rate and germination index, but decreased germination time. Moreover, there were significant interactive effects on germination traits between cold stratification and temperature. Seed germination traits showed linear relationships with latitude, indicating that S . alterniflora seeds from different provenances germinated at different times and adopted different germination strategies. The stratification and temperature are the most important factors regulating the dormancy and germination seeds, so they can be important drivers of this variation along latitude. Under scenarios of warmer regional temperature, seeds at higher latitudes could germinate earlier and have higher germination rate, which would favor a potential northern expansion of this invasive plant.

Background and aims Seed dormancy-break via cold stratification is of fundamental importance for plant adaptation to environmental conditions and response to climate change through timing germination, seedling emergence and consequently community dynamics. Although cold stratification requirements for dormancy break vary among species, it is not known if this variation is determined by the environmental conditions experienced by seeds or by differences among species. Methods We determined the soil moisture content and duration of cold stratification required for seed dormancy-break of species from alpine and desert habitats (soil moisture content: 20 and 18 species from alpine and desert habitats, respectively; duration: 16 and 16 species from the alpine and desert, respectively), and examined the correlation between environmental conditions (soil moisture content and duration of cold stratification) required for dormancy-break and seed traits. Results Seed germination increased and then decreased as soil moisture content or duration of cold stratification increased. The optimal and critical soil moisture content for seed dormancy-break were higher for alpine species than desert species. A positive correlation between optimal soil moisture content and seed shape was found. However, the duration of cold stratification required for dormancy-break was not related to habitat, seed mass or seed shape. Conclusions Our results suggest that soil moisture content rather than duration of cold stratification resulting from climate change could affect seed germination and consequently seedling emergence and establishment, especially for desert species.

The seed science community currently defines germination as radicle emergence of 2 mm from the dispersal unit. Consequently, most seed researchers abruptly terminate germination experiments after radicle emergence, concluding that the seed has germinated. However, this approach underestimates epicotyl dormancy and often leads to dormancy misclassification, or worse, a failure to identify epicotyl dormancy altogether. To address these limitations, we propose extending germination studies to the point of first leaf emergence; we term this the “full germination” period. Our methodology involves germinating fully matured, freshly collected seeds and depending on the time required for radicle emergence, the seeds are categorized into (1) viviparous, where seeds germinate prematurely while they are still attached to the parent plant or within the fruit; (2) Morphological dormancy (MD) or Non-dormant (ND), where seeds germinate within 30 days; and (3) physiological dormancy (PD) and morphophysiological dormancy (MPD), where germination does not occur within 30 days. The absence of shoot emergence within 30 days following radicle protrusion indicates the presence of epicotyl dormancy. Thus, species initially classified as ND, MD, or viviparous may be miscategorized if shoot emergence is not assessed. Likewise, seeds exhibiting PD or MPD may possess an additional epicotyl dormancy component, possibly leading to placing them in incorrect subclass or level. A comprehensive assessment of shoot development is imperative for accurate dormancy characterization. We strongly recommend monitoring seed germination until first true leaf emergence should be adopted to ensure correct conclusions about dormancy, plant life cycles and ecological adaptations.

Wild Mexican sunflower [Tithonia tubaeformis (Jacq.) Cass.] is one of the most important annual weeds for sugarcane (Saccharum spp. hybrid) and, to a lesser extent, for soybean [Glycine max (L.) Merr.] and bean (Phaseolus vulgaris L.) in the northwest of Argentina and some other countries. Currently, its management relies on chemical methods, and no information is available to develop alternative management methods. In the current study, we conducted laboratory germination assays in the presence of different conditions of light, temperature, and phytohormone (gibberellins and abscisic acid) concentrations, as well as fluridone, trinexapac-ethyl (TE), methyl viologen (MV), dry afterripening (DAR), cold stratification, and pericarp scarification. Likewise, a field experiment was carried out to assess the impact of various sugarcane crop residue amounts on seedling emergence. Darkness and constant temperatures (e.g., 20 C) reduced the germination of fresh seeds. The addition of TE, a gibberellic acid inhibitor, and abscisic acid reduced germination. In contrast, the addition of MV increased germination. Pericarp scarification and embryo excision stimulated germination, suggesting that the pericarp acts as a barrier to prevent germination. DAR did not promote germination. On the other hand, cold stratification enabled dormancy release, which in turn promoted germination when the stratified achenes germinated in light and at alternating temperatures of 20/30 C. Field experiments showed that increasing amounts of sugarcane crop residue were useful to reduce weed seedling emergence and biomass, probably by limiting the triggering effect of light and temperature alternation on seedling emergence. These findings provide information about the endogenous control of germination, which can be useful for developing a rational integrated management system for T. tubaeformis.

Background Although the effect of cold stratification on seed dormancy release has been extensively studied for many species, knowledge of the role of stratifying temperature, soil moisture content and duration of stratification on seed dormancy release at the population level is limited. Here, we aimed to determine the response of seed dormancy release to these factors in six populations of Halenia ellipti ca. Results Seed dormancy release was more responsive to low than high temperatures, and no dormancy break occurred at 8 °C. Seed germination percentage increased first and then remained unchanged as stratifying soil moisture content increased from 0 to 24%. Seed dormancy release of populations from low altitude was more sensitive to increased stratifying temperature and decreased soil moisture content than those from high altitudes. Conclusions Temperature and soil moisture changes resulting from global warming could affect seed dormancy release and consequently seedling establishment. Thus, incorporating data on seed dormancy release involving temperature, soil moisture content and stratification duration is beneficial for predicting plant species regeneration, migration and coexistence in a scenario of climate change.

Background Paeonia lactiflora Pall., a perennial plant with medicinal and ornamental value, exhibits a typical \"double dormancy\" characteristic in its seeds, which significantly limits large-scale cultivation. This study combines metabolomics and transcriptomics to explore the molecular mechanisms of dormancy release and germination in Paeonia lactiflora seeds during warm-cold stratification, focusing on hormonal regulation, metabolic pathway alterations, and gene expression changes. Methods Paeonia lactiflora seeds were subjected to stratification for 0, 28, 55, and 80 days (T0, T1, T2, T3). Endogenous hormones (ABA, GA₃, IAA) and sugars (sucrose, glucose, fructose) were quantified using high-performance liquid chromatography coupled with mass spectrometry (HPLC–MS). Nutrient contents and enzyme activities were measured using commercial kits (Solarbio), following the instructions and using standard reagents for quantification. RNA sequencing was performed for transcriptomic analysis, with differential gene expression (DEG) analysis conducted using DESeq2. Gene co-expression networks were built using weighted gene co-expression network analysis (WGCNA) to identify key regulatory modules. Results Significant changes in hormone and nutrient contents were observed during stratification. During the warm stratification phase (T0–45 days, 20 °C), ABA (abscisic acid) levels were dominant, while during the cold stratification phase (45–80 days, 4 °C), the seed’s hormonal composition underwent significant changes. ABA levels decreased from 72.54 ng/g at T0 to 1.49 ng/g at T2, GA₃ increased from 0.45 ng/g at T0 to 1.41 ng/g at T1, and IAA levels significantly increased from 4.32 ng/g at T0 to 70.09 ng/g at T1. Sugar levels showed a downward trend, with fructose content decreasing from 22.34% at T0 to 7.31% at T3. Starch content significantly decreased from 40.13% at T0 to 15.34% at T3. Enzyme activities of α-amylase and β-amylase peaked at 0.2267 U/mg and 0.3410 U/mg at T2, respectively. Transcriptomic analysis yielded 83.82 GB of high-quality clean data, identifying 83,082 differentially expressed genes (DEGs). DEG analysis revealed 11,045 DEGs during embryo axis growth (T0–T3), 10,042 DEGs during epicotyl elongation, and 923 DEGs common across all stages. WGCNA analysis identified the black, cyan, and turquoise modules as key regulatory modules related to hormonal regulation and nutrient mobilization. Pathway enrichment analysis showed that DEGs were significantly involved in metabolic pathways, including starch and sucrose metabolism, hormone signaling pathways (IAA, GA, ABA), and oxidative phosphorylation.

Most plant seeds are dispersed in a dry, mature state. If these seeds are non-dormant and the environmental conditions are favourable, they will pass through the complex process of germination. In this review, recent progress made with state-of-the-art techniques including genome-wide gene expression analyses that provided deeper insight into the early phase of seed germination, which includes imbibition and the subsequent plateau phase of water uptake in which metabolism is reactivated, is summarized. The physiological state of a seed is determined, at least in part, by the stored mRNAs that are translated upon imbibition. Very early upon imbibition massive transcriptome changes occur, which are regulated by ambient temperature, light conditions, and plant hormones. The hormones abscisic acid and gibberellins play a major role in regulating early seed germination. The early germination phase of Arabidopsis thaliana culminates in testa rupture, which is followed by the late germination phase and endosperm rupture. An integrated view on the early phase of seed germination is provided and it is shown that it is characterized by dynamic biomechanical changes together with very early alterations in transcript, protein, and hormone levels that set the stage for the later events. Early seed germination thereby contributes to seed and seedling performance important for plant establishment in the natural and agricultural ecosystem.