Several experimental tools allow researchers to manipulate environmental variables to simulate future climate change scenarios during in situ seed ecology studies. The most common ones are designed to modify a single environmental variable. For example, open-top chambers (OTCs) increase temperature or rain-out shelters decrease precipitation. However, changes in environmental variables in the future are expected to happen simultaneously, and at present, an understanding of their combined effects in natural environments is limited. Here, we present a passive novel OTC design that simultaneously increases the soil temperature and decreases soil moisture. We assessed the performance of the design during 1 year in a high-mountain environment and reported its effects on the organic and topsoil layers. The modified OTC reduced the soil volumetric water content throughout the study period. Overall, chambers increased the mean day air temperature by 3.3 °C (at 10 cm above the soil surface), the mean day soil surface temperature by 1.35 °C and the mean day below the soil surface temperature by 1.30 °C (at −5 cm) and 1.25 °C (at −10 cm). Remarkably, surface and soil temperatures remained warmer at night (+0.65 at soil surface, +0.41 at −5 cm and +0.24 at −10 cm). We detail the design plans, tools and materials needed for its construction. Furthermore, we recommend on how to use it during seed ecology studies. This tool can help increase our understanding of the potential responses of seeds and seedlings to the combined effects of warming temperatures and a decrease in precipitation.

Grass seeds play a critical and fundamental role in grass breeding and production. Elymus sibiricus L. is a widespread Poaceae forage grass in northern Eurasia which is used for ecological restoration and forage production. Sucrose is the main source of substrate and energy required for starch synthesis in the seeds, so the hydrolysis of sucrose determines and influences starch synthesis and filling in the seeds, especially Poaceae. However, the process behind carbohydrate metabolism during E. sibiricus seed development remains unclear. This study addresses a significant gap in our understanding of the carbohydrate metabolism during seed development in E. sibiricus by employing full-length transcriptome sequencing across five developmental stages for the first time. Full-length transcriptome sequencing was performed on E. sibiricus seeds at five developmental stages (S5, S9, S15, S20, S25) to get better molecular insights. We identified 13,205 differentially expressed genes, with 7,471 up-regulated and 5,734 down-regulated. Through KEGG enrichment analysis, genes were enriched in ‘starch and sucrose metabolism’, ‘photosynthetic-related’ and ‘hormone signal transduction’ pathways. Gene ontology enrichment analysis showed that genes were enriched in the ‘beta-amylase activity’ term of molecular functions. In addition, top 21 transcription factor families were identified as involved in seed development. The homologous genes of ABSCISIC ACID-INSENSITIVE 3 (ABI3), NUCLEAR FACTOR-YB1 (NF-YB1), STARCH SYNTHASE I (SSI) were identified as candidate genes of seed development in E. sibiricus. Combined with physiological index, transcriptome analyses, weighted gene co-expression network analysis and real-time quantitative PCR, the mechanism of starch and sucrose content of seed development was revealed and ten hub genes were identified. Overall, this study provides the molecular bases to understand seed development and starch and sucrose metabolism at the different seed developmental stages in E. sibiricus.

Seed dormancy in plants can have a significant impact on their ecology. Recent work by Rojas-Villa and Quijano-Abril (2023) classified the seed dormancy class in 14 plant species from the Andean forests of Colombia by using germination trials and several microscopy techniques to describe seed anatomy and morphology. The authors conclude that Cecropia species have both physical and physiological dormancy (of which they call physiophysical dormancy) based on seed morphology and mean germination times of over 30 days. Here, we present seed permeability and germination data from neotropical pioneer tree species: Ochroma pyramidale, Cecropia longipes, and Cecropia insignis, as well as Cecropia peltata (present in Rojas-Villa and Quijano-Abril, 2023), to demonstrate that Cecropia species do not exhibit dormancy and also have high levels of seed permeability. We find that the mean germination time for all three Cecropia species in our study was less than 30 days. This suggests a need for reporting the conditions in which germination trials take place to allow for comparability among studies and using seed permeability tests to accurately identify the physical dormancy class of seeds. Further, we present data from the literature that suggests that dormancy is not a requirement for seed persistence in the seed bank.

Seed germination is a pivotal period of plant growth and development. This process can be divided into four major stages, swelling absorption, seed coat dehiscence, radicle emergence and radicle elongation. Cupressus gigantea, a tree native to Tibet, China, is characterized by its resistance to stresses such as cold, and drought, and has a high economic and ecological value. Nevertheless, given its unique geographic location, its seeds are difficult to germinate. Therefore, it is crucial to explore the mechanisms involved in seed germination in this species to improve the germination efficiency of its seeds, thereby protecting this high-quality resource. Here, our findings indicate that seed germination was enhanced when exposed to a 6-h/8-h light/dark photoperiod, coupled with a temperature of 20°C. Furthermore, the application of exogenous GA3 (1 mg/ml, about 2.9 mM) stimulated the germination of C. gigantea seeds. Subsequently, proteomics was used to detect changes in protein expression during the four stages of seed germination. We identified 34 differentially expressed proteins (DEPs), including 13 at the radicle pre-emergence stage, and 17 at the radicle elongation stage. These DEPs were classified into eight functional groups, cytoskeletal proteins, energy metabolism, membrane transport, stress response, molecular chaperones, amino acid metabolism, antioxidant system and ABA signalling pathway. Most of them were found to be closely associated with amino acid metabolism. Combined, these findings indicate that, along with temperature and light, exogenous GA3 can increase the germination efficiency of C. gigantea seeds. Our study also offers insights into the changes in protein expression patterns in C. gigantea seeds during germination.

Seed dormancy is an important trait associated with pre-sprouting and malting quality in barley. Genome-wide association studies (GWASs) have been used to detect quantitative trait loci (QTLs) underlying complex traits in major crops. In the present study, we collected 295 barley (Hordeum vulgare L.) accessions from Australia, Europe, Canada and China. A total of 25,179 single nucleotide polymorphism (SNP)/diversity arrays technology sequence markers were used for population structure, linkage disequilibrium and GWAS analysis. Candidate genes within QTL regions were investigated, and their expression levels were analysed using RNAseq data. Five QTLs for seed dormancy were identified. One QTL was mapped on chromosome 1H, and one QTL was mapped on chromosome 4H, while three QTLs were located on chromosome 5H. This is the first report of a QTL on the short arm of chromosome 5H in barley. Molecular markers linked to the QTL can be used for marker-assisted selection in barley breeding programmes.

Time-separated seed collections with a separation period of 12–18 years were used to study recent changes in germination traits and the role of climate factors in seven tropical dry forest (TDF) woody species in Zambia, southern Africa. In all the species, peak and final germination were lower in recent (2016–2021) seed collections than in historic (1998–2005) seed collections during the first germination season. However, in species with seed dormancy, both peak and final germination after one year burial were higher in recent seed collections than in historic seed collections. Three monthly climate factors had significant effects on final germination in the different species and the timing of most of these factors was during seed development and ripening that suggest that these factors operated through mother plants. In species with seed dormancy, post-first-year germination of buried seeds responded to climate factors in the regeneration niche. Climate factors that significantly affected germination included those that changed over the separation period between historic and recent seed collections. This indicates that short-time climatic changes may have the potential to impact germination in TDF woody species of southern Africa. The germination responses to climate factors were both positive and negative and it is not clear whether these are adaptations or not. Further research is required to assess the adaptive significance of these changes in germination traits in TDF species of southern Africa.

Alpine plant species are particularly vulnerable to climate change. Temperature fluctuations are projected to be most severe at high elevations. Even small shifts in temperature have major consequences on phenology, reproduction, and community composition. Early life stages are arguably the most important processes in the fitness of an individual plant and the dynamics and persistence of plant populations. These initial developmental stages are expected to be more vulnerable to changes in climate than adult life stages. To understand how early life stages of alpine plant species will respond to warming temperatures, seeds and seedlings of two species were exposed to three different temperature regimes. Temperatures were based on current and projected conditions under low and high emission scenarios. Two rare alpine species performed better under warmer temperatures at both the germination and seedling stages. The results show that early life stages of alpine plants may not be at high risk from warming temperatures; however, there are many other shifting climatic factors to consider, resulting from climate change beyond temperature alone.

The assessment of seed quality and physiological potential is essential in seed production and crop breeding. In the process of rapid detection of seed viability using tetrazolium (TZ) staining, it is necessary to spend a lot of labour and material resources to explore the pretreatment and staining methods of hard and solid seeds with physical barriers. This study explores the TZ staining methods of six hard seeds (Tilia miqueliana, Tilia henryana, Sassafras tzumu, Prunus subhirtella, Prunus sibirica, and Juglans mandshurica) and summarizes the TZ staining conditions required for hard seeds by combining the difference in fat content between seeds and the kinship between species, thus providing a rapid viability test method for the protection of germplasm resources of endangered plants and the optimization of seed bank construction. The TZ staining of six species of hard seeds requires a staining temperature above 35 °C and a TZ solution concentration higher than 1%. Endospermic seeds require shorter staining times than exalbuminous seeds. The higher the fat content of the seeds, the lower the required incubation temperature and TZ concentration for staining, and the longer the staining time. And the closer the relationship between the two species, the more similar their staining conditions become. The TZ staining method of similar species can be predicted according to the genetic distance between the phylogenetic trees, and the viability of new species can be detected quickly.

This work provides insights into the deterioration of cacti seeds of Escontria chiotilla (F.A.C. Weber ex K. Schum) and Stenocereus pruinosus (Otto ex Pfeiff.) Buxbaum stored ex situ at 25 °C, under dry and dark conditions or buried in situ conditions in a xerophytic shrubland. Viability, germination speed, electrolyte leakage and indicators of the redox balance including glutathione content, glutathione half-cell reduction potential (EGSSG/2GSH) and malondialdehyde (MDA), oxidized protein content, together with water-soluble antioxidant enzyme activity were assessed. Over a period of two years of storage, viability was maintained when seeds were stored ex situ at 7–9% water content compared to seeds buried in the soil. A second burial experiment showed that seeds of E. chiotilla maintained viability during a year of storage that included a rainy season followed by a dry season. Thereafter, they died rapidly during the second rainy season. In contrast, those of S. pruinosus started to lose viability after 6 months of burial at the end of the rainy season and were mostly dead at the end of the dry season. This difference in persistence between species was related to a difference in the glutathione content and antioxidant enzyme activities. In both storage experiments, the loss of viability of both species was associated to a EGSSG/2GSH shift to a more oxidative state during burial. Yet, contents in MDA and oxidized soluble proteins were not related to redox imbalance and loss of viability, indicating that these compounds are not good markers of oxidative stress in cacti seeds during storage.

The germination percentage (GP) is commonly employed to estimate the viability of a seed population. Statistical methods such as analysis of variance (ANOVA) and logistic regression are frequently used to analyse GP data. While ANOVA has a long history of usage, logistic regression is considered more suitable for GP data due to its binomial nature. However, both methods have inherent issues that require attention. In this study, we address previously unexplored challenges associated with these methods and propose the utilization of a likelihood ratio test as a solution. We demonstrate the advantages of employing the likelihood ratio test for GP data analysis through simulations and real data analysis.

Climate variability is expected to increase due to climate change, with projected increases in temperature and erratic rainfall patterns. These changes will alter the environmental cues sensed by seeds, and therefore will impact plant recruitment. This study investigated the effects of seed functional traits (germinability, germination time, synchrony and seed mass) on germination responses of several sub-tropical native Australian plant species under different environmental factors (water stress, salinity and pH). The effect of a hot water pre-treatment was also tested on Fabaceae seeds with known physical dormancy. Seed traits, environmental factors and seed pre-treatments had significant effects on final germination percentage and germination time. Seed mass and time to 50% germination (t50) were also positively correlated. In contrast, pH did not affect germination and there was no interaction between pH and any of the measured seed functional traits. Some species showed a high thermal tolerance to germination and germination was indifferent to light conditions for all species. Results showed that certain seed functional traits interact with environmental factors to influence germination percentage and time. These findings highlight the importance of considering seed functional traits when determining a species germination response under a changing climate. In addition, the findings provide important knowledge to better guide seed-based land restoration programmes.

Desiccation tolerance (DT) of seeds, one of the plant's environmental adaptation mechanisms, allows them to survive as seeds in a quiescent state under extremely water-deficient conditions during the plant's life cycle, followed by seed germination and seedling establishment under favourable water conditions. The seed-DT is lost after radicle emergence; however, there is a developmental period called the ‘DT window’ during which the germinating seeds can re-induce DT following a cue from their ambient low water potential (i.e. mild osmotic stress). The DT re-inducibility within the DT window has been used as a model biosystem for understanding molecular mechanisms that activate/supress DT in a number of plant species. However, the characteristics of the DT window for species particularly important to the agroindustry are still largely fragmented. Here, physiological analyses were performed, aiming to elucidate the properties of the DT window in tomato, a model species for Solanaceae, holding a key strategic position for the seed industry and commercial use around the world. We revealed that (i) the DT window of tomato seeds is closed when the developing radicle reaches about 4 mm after germination, (ii) the most effective ambient water potential to re-induce DT into seeds is about −1.5 MPa and (iii) there is organ specificity of DT re-induction with hypocotyls, showing a longer DT window than cotyledons and roots in post-germination seeds.

‘Seed heteromorphism’ is a broadly- and loosely-defined term used to describe differences in size/mass, morphology, position on mother plants and ecological function (e.g. dispersal, dormancy/germination) of two or more seeds or other diaspores produced by an individual plant. The primary aim of this review paper was to characterize via an in-depth classification scheme the physical structural design (‘architecture’) of diaspore monomorphism and diaspore heteromorphism in angiosperms. The diaspore classification schemes of Mandák and Barker were expanded/modified, and in doing so some of the terminology that Zohary, Ellner and Shmida, and van der Pijl used for describing diaspore dispersal were incorporated into our system. Based on their (relative) size, morphology and position on the mother plant, diaspores of angiosperms were divided into two divisions and each of these into several successively lower hierarchical layers. Thus, our classification scheme, an earlier version of which was published in the second edition of ‘Seeds’ by Baskin and Baskin, includes not only heteromorphic but also monomorphic diaspores, the Division to which the diaspores of the vast majority of angiosperms belong. The scheme will be useful in describing the ecology, biogeography and evolution of seed heteromorphism in flowering plants.

Statistical significance, or lack thereof, is often erroneously interpreted as a measure of the magnitude of effects, correlations between variables or practical relevance of research results. However, calculated P-values do not provide any information of this sort. Alternatively, effect sizes as measured by effect size indices provide complementary information to results of statistical hypothesis testing that is crucial and necessary to fully interpret data and then draw meaningful conclusions. Effect size indices have been used extensively for decades in the medical, psychological and social sciences but have received scant attention in the plant sciences. This Technical Update focuses on (1) raising awareness of these important statistical tools for seed science research, (2) providing additional resources useful for incorporating effect sizes into research programmes and (3) encouraging further applications of these tools in our discipline.

Small isolated plant populations are one of the consequences of fragmentation of natural habitats by humans. We asked what effect does the creation of smaller populations from larger ones has on the plant fitness-related trait seed germination. Using information on 119 species (142 species entries) in 50 families, we found that seeds in only 35.2% of the species entries from larger populations germinated to higher percentages than those from smaller populations. In the other entries, seeds from large and small populations germinated equally well (57.7% of total entries) or seeds from small populations germinated better (7.0% of total entries) than those from large populations. These results indicate that population size is not a reliable predictor of seed germinability. Furthermore, there was little relationship between seed germination and either seed mass, genetic diversity or degree of population isolation, or between population size and genetic diversity.

The intraspecific variations of phenotypic traits in the early life stages, such as seed germination and seedling establishment, are important components affecting species adaptation and differentiation. As one of the most common ways in which seeds are maintained, dry storage usually affects these traits, by either increasing or decreasing variation among populations. However, little is known about how the interaction between dry storage and population variation of a species affects the performance and adaptability of early life-cycle traits. In this study, we conducted experiments with seeds from ten populations of Elymus nutans along an altitudinal gradient on the eastern Qinghai-Tibet Plateau. Fresh seeds and seeds stored dry for 6 months were used to quantify the temperature thresholds for germination, determine seedling emergence and survival in two common gardens and examine the correlation between these traits and environmental conditions of population provenance. Dry storage increased germination percentage, germination speed and seedling emergence, and decreased intraspecific variation in germination traits of seeds (reduced by 33.36, 52.05 and 20.45% for Tb, θT(50) and σθT, respectively). Dry storage had little effect on the intraspecific variation of seedling emergence and survival. In addition, the temperature threshold for germination cannot be used to predict seedling emergence and survival in either common garden, regardless of whether seeds were stored or not. These results indicated that it is feasible to use dry-stored seeds to evaluate and select suitable provenances in ecological restoration, and using dry-stored seeds in ecological restoration projects is expected to achieve better vegetation restoration results than fresh seeds. On the other hand, the status of seeds (fresh vs. dry stored) should be considered in an evaluation of the adaptive value of plant functional traits, especially in the early life stages, otherwise, inconsistent conclusions may be drawn.

In this review, we explore the origin of the rudimentary embryo, its relationship to other kinds of plant embryos and its role in the diversification of angiosperms. Rudimentary embryos have a length:width ratio of ≤2.0, and they have organs, including cotyledon(s) and a primary root. A literature survey failed to reveal rudimentary embryos in the pre-angiosperms, suggesting that this kind of embryo is an angiosperm invention. Although proembryos of some gymnosperms and angiosperms have a length:width ratio of ≤2.0, they have not formed meristems or organs. Thus, rudimentary embryos are not proembryos. During the development of rudimentary embryos in monocots and dicots (all non-monocots), the growth pattern of the epicotyledonary cells differs, resulting in differences in the placement of the shoot meristem and in one versus two cotyledons, respectively, but the embryo size is similar. Rudimentary embryos grow inside the seed prior to germination, which is true for linear-underdeveloped embryos, including those in some gymnosperms. Rudimentary embryos served as the starting point for the great diversification of embryos, and ultimately of seeds, in angiosperms, and they are still present in many families of extant angiosperms. The rudimentary embryo is part of the syndrome of changes, including increased speed of pollen germination and pollen tube growth, simplification of the female gametophyte, development of endosperm and elimination of multiple embryo production from each zygote, that distinguish angiosperm seed production from that of gymnosperms. We conclude that the rudimentary embryo was one of many new developments of angiosperms that contributed to their great success on earth.

Understanding seed moisture desorption and adsorption isotherms is important for seed quality maintenance and better predicting seed storage lifespan. Freshly harvested oilseed rape and barley seeds were dried and then rehydrated twice. Seed equilibrium relative humidity (eRH) and moisture content (MC) were determined at different humidity levels so that two cycles of desorption and adsorption could be constructed. In addition, seeds were dried to 30% RH and then rehydrated to 50% RH for five cycles to determine whether they shift to the adsorption isotherm. Monolayer MC was determined using the Gugenheim-Anderson-de Boer model. Storage experiments were conducted for seeds equilibrated at 30, 40, 50, 60 and 70% RH for two cycles of desorption and adsorption at 45°C. Isotherm curves’ shapes were similar for oilseed rape and barley, although spanning a greater MC range in barley. The hysteresis effect was observed for oilseed rape and barley seeds when dried over silica gel at <10% RH. However, this effect was only observed for barley seeds when dried to 30% RH, but not for oilseed rape seeds. Longevity was greater for adsorbing seeds than desorbing seeds at a given eRH, however, there was no significant difference in σ (the standard deviation of the normal distribution of seed deaths over time)–MC log–log relationship. The relationship shifted for seeds on the second cycle. In conclusion, if seed lots are stored at a specific RH, reaching equilibrium by desorption or adsorption can strongly influence their longevity. Also, when seeds of different species are dried to low RH, they will respond differently to a subsequent increase in RH, which could profoundly affect their longevity.

The Asteraceae with up to 30,000 species occurs on all continents except Antarctica and in all major vegetation zones on earth. Our primary aim was to consider cypselae dormancy-break and germination of Asteraceae in relation to ecology, vegetation zones and evolution. Cypselae are desiccation-tolerant and in various tribes, genera, species and life forms of Asteraceae are either non-dormant (ND) or have non-deep physiological dormancy (PD) at maturity. All six types of non-deep PD are found among the Asteraceae, and dormancy is broken by cold or warm stratification or by afterripening. Soil cypselae banks may be formed but mostly are short-lived. Much within-species variation in dormancy-break and germination has been found. Using data compiled for 1192 species in 373 genera and 35 tribes of Asteraceae, we considered ND and PD in relation to life form, vegetation zone and tribe. Senecioneae and Astereae had the best representation across the vegetation zones on earth. In evergreen and semi-evergreen rainforests, more species have ND than PD, but in all other vegetation zones, except alpine/high-latitude tundra (where ND and PD are equal), more species have PD than ND. Tribes in the basal and central grades and those in the Heliantheae Alliance have both ND and PD. The high diversity and lability of non-deep PD may have enhanced the rate of species diversification by promoting the survival of new species and/or species in new habitats that became available following globally disruptive events since the origin of the Asteraceae in the Late Cretaceous.