Abstract The Malvaceae is the 12th largest angiosperm family with ten subfamilies, 243 genera and c. 4000 species of trees, shrubs, herbs and a few climbers. Subfamilies originated in the Upper Cretaceous-Palaeocene, and their divergence times range from 71.6 to 33.0 Ma. Seeds have a folded, investing or spatulate embryo, and they may be nondormant (ND) or have physical (PY) and/or physiological (PD) dormancy. Of the 365 species for which dormancy/germination data were found, 34.0% had ND seeds and 46.6% PY; 1.6%, PD&ND; 13.1%, PY&ND; and 4.7% PY+PD. Seeds with PY have a palisade layer of Malpighian cells (with a light line) in the outer epidermis of the inner integument, and a chalazal plug is the water gap. Seeds of 168 species of wet tropical trees, in all ten subfamilies, were ND (57.2%) or had PY (19.7%), but seed collections of many species were a mixture of ND & PY (20.2%); 2.9% had PD&ND. We found 13 tree species in wet tropics with recalcitrant seeds and 57 species in 28 genera in seven subfamilies in various habitats with persistent soil seed banks. Malvoideae is the most species rich and widely distributed subfamily and is found in tropical and temperate regions but rarely in subalpine/boreal or Arctic/alpine tundra vegetation. Few if any Malvaceae, in particular Malvoideae, grow as herbaceous perennials in tundra vegetation; possible reasons for this are considered.

Abstract The genetic basis of rapid and uniform seed germination and its associated traits is crucial for improving seed vigour and seedling establishment for higher productivity in direct-seeded rice (DSR) systems. This study investigates the phenotypic diversity and genetic architecture of germination traits in 163 rice genotypes, using a genome-wide association studies (GWAS). An association panel of 163 diverse rice genotypes, including varieties, germplasm and breeding lines, was evaluated for seed germination traits over 2 years (2022 and 2023). The panel was genotyped using 295 simple sequence repeat (SSR) markers, including 80 random SSRs and 215 candidate gene SSRs linked to seed traits and morphological attributes. The genotyping of 163 lines with 295 markers revealed a range of genetic diversity, with polymorphic information content values between 0.04 and 0.93. Population structure analysis indicated the presence of two groups and four sub-groups. GWAS identified 80 significant marker-trait associations (MTAs) across 12 chromosomes at P ≤ 0.05, which narrow down to 18 MTAs at P ≤ 0.01. Twelve candidate genes are identified which were related with multiple traits, linked to important functions, such as seed-size regulation, nutrient mobilization and plant growth. Candidate gene-based SSR (cgSSR) markers such as M169 (OsMIK), M57 (THIS1), M66 (GW2), and M18 (OsBAK1), displayed pleiotropy including rapid and uniform germination (germination index, germination rate index and mean germination time) traits. The newly identified candidate gene markers associated with seed rapid and uniform germination traits can be leveraged in marker-assisted breeding programs to introduce diverse alleles for enhanced seed vigour and crop establishment. Markers closely linked to multiple traits hold significant potential for the simultaneous improvement of several traits.

Abstract Cumin ( Cuminum cyminum L.) is an annual herbaceous plant from the Apiaceae family, renowned for its medicinal and culinary applications as the second most popular spice globally after black pepper. Germination is a critical stage in the life cycle of plants, particularly for medicinal plants, as it determines successful establishment and productivity. This study explores the impact of ploidy levels (diploid and tetraploid) and genotype interactions on germination traits, seed morphology and early seedling growth in five selected cumin genotypes (YAR1, KBA4, SKD6, SIV8 and NKM9). Induction of tetraploidy significantly influenced germination percentage, rate, seed vigour index, and morphological traits. Notably, diploid genotypes exhibited higher germination percentages, while tetraploid SKD6 displayed the highest germination speed and seedling biomass, demonstrating genotype-specific ploidy effects. For the first time, root growth kinetics were analyzed, revealing distinct growth patterns between diploid and tetraploid seeds. Morphometric evaluations showed that tetraploid seeds and embryos were significantly larger, attributed to the ‘gigas effect’, which enhances storage reserves and seed vigour. However, challenges such as embryo-less seeds and variability in genotype responses to ploidy manipulation were observed. These findings underscore the importance of targeted breeding strategies that optimize genotype-ploidy interactions to improve seed quality, germination performance and early growth in cumin. By advancing our understanding of polyploidy’s role in shaping key agronomic traits, this study provides a foundation for sustainable cultivation practices and enhanced productivity of medicinal plants.

Abstract Seed dormancy is the key factor determining weed emergence patterns in the field. Alopecurus myosuroides (black grass) is a serious cereal weed in Europe that experiences two emergence peaks affecting winter and spring cereals, respectively. Seedlings that emerge in autumn encounter a period of cold winter temperatures, whereas those that emerge in spring do not. In this work, we investigated the effects of this overwintering during vegetative growth on the primary seed dormancy of the offspring. Alopecurus myosuroides plants were propagated under controlled conditions where a proportion of the population was subjected to a simulated winter period (vernalization) as seedlings. The offspring produced by vernalized plants was significantly more dormant, requiring longer after-ripening and cold stratification treatments to germinate at warm temperatures. However, there was no difference in the range of temperatures under which dormant seeds germinated. We hypothesized that this difference in dormancy was the result of an epigenetic memory of vernalization. Global changes in DNA methylation of seeds were quantified using an ELISA-based approach. Imbibition in dormant seeds produced by vernalized plants was associated with a global demethylation event that was not observed in the offspring of plants that had not been vernalized. Taken together, these results demonstrate the importance of temperature at different stages of the plant lifecycle in determining dormancy levels and consequently weed emergence patterns in the field.

Abstract 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.

Abstract The Myrtaceae is the ninth largest angiosperm family with c. 6000 species, and it diverged from its closest relative the Vochysiaceae c. 100 Ma in southern Gondwana before the final separation of South America and Australia from Antarctica. The family has trees and shrubs and a few viny epiphytes but no herbs and mainly occurs in the tropics and in temperate regions with a Mediterranean climate. Numerous fleshy-fruited species and dry-fruited species have evolved in moist and seasonally dry (fire-prone) regions, respectively. Five kinds of fully developed embryos are found in Myrtaceae seeds, and at maturity seeds are either nondormant (ND) or have physiological dormancy, regardless of embryo morphology, kind of fruit produced, life form, habitat/vegetation region or tribe. Dormant seeds of fleshy-fruited species in wet habitats become ND and germinate at high temperatures. Dormant seeds of dry-fruited species in seasonally dry habitats become ND during the hot, dry season and germinate with the onset of the wet season; seeds germinate only at high temperatures or over a range of low to high temperatures, depending on the species. Seeds of fleshy-fruited species are animal-dispersed, and some Myrteae and Syzygieae are desiccation-sensitive and/or exhibit totipotency. Relatively few species form a persistent soil seed bank, but many dry-fruited species in fire-prone habitats form an aerial seed bank (serotiny). Heat and smoke from fires have a negative, neutral or positive effect on germination, depending on the species. Challenges for maintaining the high species richness of Myrtaceae include habitat destruction/fragmentation, pathogenic fungi and climate change, especially patterns of precipitation.

Abstract Leonurus cardiaca is a perennial mint species with a long history of use as a medicinal herb. It produces a wide variety of phytochemicals with pharmacological properties that are used to treat anxiety and sleep disorders, cardiac disorders, and to reduce inflammation. Surprisingly, scant information is available concerning its seed germination ecology. Hence, this study investigated the presence/kind of seed dormancy and the effects of several environmental factors on seed germination and seedling emergence. Seeds were collected from three populations, and they were subjected to germination and seedling emergence experiments in which environmental factors, including temperature, light, cold stratification, pH, osmotic stress, and depth of burial, were manipulated. Non-stratified seeds germinated over a range of alternating temperature regimes from 20/10 to 30/20°C, but they did not germinate at 15/5°C. Optimum germination occurred between 25/15 and 30/20°C. The presence or absence of light did not affect germination. Cold stratification at 4°C enhanced germination at the two coolest temperature regimes. Seed germination occurred over a solution pH range of 5–10 and exceeded 55% in buffer solutions with pH 6–10. Low levels of osmotic stress reduced germination; only 3–8% of seeds germinated at −0.2 MPa. Maximum seedling emergence occurred when seeds were placed on the soil surface, and emergence decreased with increased burial depths to 5 cm. Overall, seeds exhibited germination characteristics associated with type 2 non-deep physiological dormancy at maturity. Seeds primarily germinated at incubation temperatures of ≥ 25/15°C; however, conditionally dormant seeds became nondormant after prolonged exposure to cold stratification.

Abstract Seeds are complex structures that serve as dispersal units in angiosperms. Seeds consist of three specialized tissues with distinct roles and molecular compositions. Hence, the characterization of the genetic regulators that act within individual seed tissues, and how their activity changes during seed development and germination, has been a primary focus of seed research. However, our knowledge of the spatiotemporal modulation of genetic regulators within seeds, across different seed cell types, has been limited by the resolution of available techniques. In the last few years, the development and application of single-cell technologies in plants have enabled the elucidation of gene networks involved in various developmental processes at the cellular level. Some studies have applied these technologies to seeds, enabling further characterization of seed development and germination at the cellular level. Here, we review the current status of the application of single-cell technologies to seeds and present a workflow for conducting single-cell transcriptomics. Additionally, we discuss the integration of single-cell multi-omics, aiming to demonstrate the potential of single-cell technologies in enhancing our comprehension of the spatiotemporal regulations governing seed development and germination.

Abstract Seed biopriming with Pseudomonas fluorescens as a beneficial microbial inoculant and seed hydropriming with deionized water were conducted with oilseed rape (Brassica napus). Both techniques involve restricted seed hydration followed by seed drying. Seed biopriming reduced the uniformity (time difference between 10 and 90% germination) of germination ca 4-fold, without changing the maximum germination percentages (Gmax) of seed populations. In contrast to this, seed hydropriming improved the uniformity, but not for aged seed populations. The distinct effect of biopriming on germination was caused by the high salt concentration in the priming medium, not by the bacteria or any of the other components. The effects of biopriming duration, seed input and temperature (incubation and drying) were tested and the number of bacteria attached to the seed coat surface was between 1.6 × 106 and 9.8 × 108 colony-forming units (CFUs) per seed. Long-term storage (21°C, <10% relative humidity, 21% oxygen) of dry bioprimed seeds resulted in a rapid decline of bacterial viability, for example (6 h biopriming, 50 g seed input) from 9.8 × 108 CFU per seed to 7.3 × 104 after 4 weeks and 5.0 × 102 after 12 weeks of air-dry seed storage. Seed biopriming and long-term storage of dry bioprimed seeds did not affect Gmax at optimal (24°C) and cold-stress (16°C) temperatures, and did not appreciably affect early seedling growth. Additive biopriming with kimchi paste did not affect the number of bacteria attached per seed but caused an ~800-fold increase in retaining bacterial viability during long-term seed storage.

Abstract Seed persistence, desiccation tolerance, and dormancy play a crucial role in plant population and community dynamics. However, these life-history traits remain largely understudied in perennial herbaceous species, particularly in tropical ecosystems. We evaluated the seed storage behaviour, potential longevity, soil seed bank, seed dormancy alleviation in the field and the effects of after-ripening temperature and time on seed dormancy alleviation in Carajasia cangae – an endangered perennial forb endemic to the ironstone outcrops of the Eastern Amazon. We performed germination experiments to examine the effect of storage conditions (−20, 5 and 28°C, as well as field storage) and time on seed viability, mean germination time and percentage. Our results suggested that C. cangae seeds form a transient soil seed bank and show orthodox storage behaviour. The seeds' longevity was favoured in all controlled storage conditions in relation to soil-stored seeds (field). However, the marked loss of seed viability in less than 1 year, regardless of storage condition, indicates a low potential for long-term germplasm conservation through seed banking. Seed dormancy was fully alleviated after 3 months of field storage during the dry season. Moreover, seeds stored for 6 months at 28°C had their dormancy partially alleviated, indicating that environmental conditions found throughout the dry season in the species habitat are required to alleviate its seed dormancy. A transient seed bank type is favoured by predictable seasonal variations in climate in the region, species iteroparity and seed dormancy alleviation during the dry season, which delays germination until the onset of the next rainy season.