Germination Niche Research Articles

Cooperation between primary cilia signaling and integrin receptor extracellular matrix engagement regulates progenitor proliferation and neuronal differentiation in the developing cerebellum.

Neural progenitors and their neuronal progeny are bathed in extrinsic signals that impact critical decisions like the mode of cell division, how long they should reside in specific neuronal laminae, when to differentiate, and the timing of migratory decisions. Chief among these signals are secreted morphogens and extracellular matrix (ECM) molecules. Among the many cellular organelles and cell surface receptors that sense morphogen and ECM signals, the primary cilia and integrin receptors are some of the most important mediators of extracellular signals. Despite years of dissecting the function of cell-extrinsic sensory pathways in isolation, recent research has begun to show that key pathways work together to help neurons and progenitors interpret diverse inputs in their germinal niches. This mini-review utilizes the developing cerebellar granule neuron lineage as a model that highlights evolving concepts on the crosstalk between primary cilia and integrins in the development of the most abundant neuronal type in the brains of mammals.

The Adult Carotid Body: A Germinal Niche at the Service of Physiology.

The carotid body is the most relevant oxygen sensor in mammalian organisms. This organ helps to detect acute changes in PO2, but it is also crucial for the organismal adaptation to a maintained hypoxemia. Profound angiogenic and neurogenic processes take place in the carotid body to facilitate this adaptation process. We have described a plethora of multipotent stem cells and restricted progenitors, from both vascular and neuronal lineages, existing in the quiescent normoxic carotid body, ready to contribute to organ growth and adaptation upon the arrival of the hypoxic stimulus. Our deep understanding of the functioning of this stunning germinal niche will very likely facilitate the management and treatment of an important group of diseases that course with carotid body over-activation and malfunction.

Germination niche of a neotropical dry forest species: seed osmotic stress and recovery

Abstract: Erythrina velutina Willd is a native Fabaceae with wide occurrence, mainly in the Caatinga Domain with multiple uses. This study aimed to compare the vulnerability/tolerance of seeds of four accessions of E. velutina to osmotic stresses. Four replications were conducted with 25 seeds, germinated in osmotic solutions of NaCl or PEG up to -1.73 MPa. Seeds that did not germinate after 14 days were recovered in distilled water. Obtained data were fitted in Boltzmann curves and t50 and synchrony were evaluated. A probit analysis was performed, and hydrotime and halotime models were constructed. In distilled water, the germination curve was similar for all accessions. When the concentration of salt or PEG in the substrate increased, the accessions differentiated into two groups. Two accessions - Jutaí 2012 and Jutaí 2015 - maintained high germination up to -0.86 MPa NaCl, while Caboclo 2008 and Caiçara 2011 accessions presented a lower germination speed. The hydrotime and halotime analyses separated the germination response of accessions according to their physiological quality and tolerance to osmotic and saline conditions. Seeds viability was maintained at both stresses, since germination was reestablished at distilled water, thus constituting a crucial response for this species’ survival and conservation.

MiR-17∼92 exerts stage-specific effects in adult V-SVZ neural stem cell lineages.

Neural stem cells (NSCs) in the adult ventricular-subventricular zone (V-SVZ) generate neurons and glia throughout life. MicroRNAs are important post-transcriptional regulators frequently acting in a context-dependent manner. Here, microRNA profiling defines cohorts of miRNAs in quiescent and activated NSCs, with miR-17∼92 highly upregulated in activated NSCs and transit amplifying cells (TACs) versus quiescent NSCs. Conditional miR-17∼92 deletion in the adult V-SVZ results in stage-specific effects. In NSCs, it reduces proliferation invitro and invivo, whereas in TACs, it selectively shifts neurogenic OLIG2- DLX2+ toward oligodendrogenic OLIG2+ DLX2- TACs, due to de-repression of an oligodendrogenic program, leading to increased oligodendrogenesis invivo. This differential regulation of TAC subpopulations highlights the importance of TAC heterogeneity. Finally, in the NSC lineage for intraventricular oligodendrocyte progenitors, miR-17∼92 deletion decreases proliferation and maturation. Together, these findings reveal multiple stage-specific functions of the miR-17∼92 cluster within different adult V-SVZ lineages.

Seed traits inform the germination niche for biodiverse ecological restoration

Seeds are a primary source for generating plants for large-scale restoration and understanding the requirements for seed germination and establishment is fundamental to ecological restoration. Seed germination traits are central to defining the germination niche and identifying traits that may limit seedling establishment provides insights into how seeds may interact with the abiotic environment and the soil substrates specific to each restoration site and informs seed management practices. In this paper we review seed trait data derived from research to improve restoration practice across diverse ecosystems within Western Australia. We compile and evaluate seed trait data for up to 300 seed collections of 287 species that are used in restoration programmes to identify species, lifeform, and region-specific variation in seed dormancy, maximum germination, germination speed, base water potential, and germination niche breadth. Through a synthesis of this data, we outline our ecologically-guided approach to identifying key seed traits that support plant regeneration to improve the success of seed-based restoration across the biodiverse Western Australian landscape.

Seed germination thermal niche differs among nine populations of an annual plant: A modeling approach.

Germination timing is an important determinant of survival and niche breadth of plants. The annual plant Nigella sativa occurs in diverse environments along a steep temperature gradient and thus is a suitable model for the study of germination behavior in response to temperature. We used a modeling approach to compare the germination thermal niche of seeds of nine populations of N. sativa produced in a common garden. Germination time courses were obtained by a newly developed process‐based model, and thermal niche was visualized by plotting germination breadth as a function of after‐ripening time. Seeds were sampled five times: immature (2 weeks before maturity), mature, and afterripened for 1, 2, and 5 months. Immature and mature seeds had a greater depth of dormancy than afterripened seeds, as estimated by lower values of high‐limit temperatures (T h). Afterripening increased germination percentage, synchrony, and thermal niche breadth of all nine populations. The highest asynchrony was for immature and mature seeds, and afterripening enhanced synchrony. Based on the new graphical method, N. sativa has Type 1 nondeep physiological dormancy, and thus, the germination niche is narrow at seed maturity, leading to a delayed germination strategy that is highly dependent on thermal time accumulated during afterripening. Our findings show that there is considerable variation in the germination thermal niche among populations. Temperature regimes in the natural habitats of N. sativa have played a significant role in shaping variation in thermal niche breadth for seed germination of this annual species. The models used in our study precisely predict germination behavior and thermal niche under different environmental conditions. The germination synchrony model also can estimate germination pattern and degree of dormancy during the year, suggesting a useful method for quantification of germination strategies.

Recruitment varies among milkweed seed sources for habitat specialist but not generalist

If sufficient seedling establishment can be achieved, seed‐based restoration provides an affordable, active restoration approach that can be implemented quickly at scale. However, establishment has served as a major restoration bottleneck, highlighting the need for improved understanding of seed germination niche and interactions with site conditions. Germination niche breadth (NB) is expected to increase with gene flow, resulting in broader environmental tolerance range, reduced sensitivity to site conditions, and less variation among seed sources. To investigate how germination NB relates to inter‐ and intraspecific variation in establishment from seed, we compared field recruitment for two milkweeds (Asclepias), the larval host plant of the monarch butterfly and thus a high priority group for habitat creation. Consistent with species‐level NB derived from laboratory trials, there was strong evidence that early life stages of the habitat specialist (Asclepias incarnata) varied among seed collection regions (separated by 423–572 km) but no evidence that the generalist (A. syriaca) varied among seed sources collected across an approximately 750‐km transect. Regeneration trends demonstrate that A. incarnata is significantly more sensitive to seed source and therefore requires more restricted seed zones. However, climate change may necessitate that we separate seed collection zones from seed application zones, upending the traditional framework of seed transfer zones. Until taxon‐specific studies have identified the scale of adaptive, phenotypic variance, restoration practitioners should continue to adjust the scale of seed collection zones for milkweeds and other taxa based on species traits known to influence gene flow, such as abundance and habitat specificity.

Germination niche breadth of invasive Iris pseudacorus (L.) suggests continued recruitment from seeds with global warming.

PremiseUnderstanding recruitment processes of invasive species is central to conservation and management strategies. Iris pseudacorus, an emergent macrophyte, has established invasive populations across a broad global range, and reduces biodiversity in wetland ecosystems. Climate change is altering germination cues, yet studies on the invasion of wetland macrophytes often ignore germination ecology despite its importance to their establishment and spread.MethodsWe explored germination of seeds from invasive I. pseudacorus populations in California in response to seed coat presence or absence, and several environmental factors. Using experimental results in a thermal time model, we derived germination temperature thresholds.ResultsGermination of I. pseudacorus seeds did not require cold or warm stratification, and was not affected by seed coat presence or absence. Germination occurred in the dark, although germinability was two‐ to threefold times greater under light. At constant temperature, thermal time model estimates included 18.3 ± 1.8°C base germination temperature (Tb); 28.2 ± 0.5°C optimal temperature (To); and 41.0 ± 1.7°C ceiling temperature (Tc). Seeds exposed to 36.0°C achieved over 10% germination, and embryos of ungerminated seeds presented 76% viability. Overall, germinability remained relatively low at constant temperatures (≤25%) but was close to 90% under alternating daily temperatures.ConclusionsExposure to diurnally fluctuating temperatures is essential for this species to achieve high germination rates. Our study reveals that I. pseudacorus has a broad germination niche supporting its establishment in a relatively wide range of environments, including at high temperatures more frequent with climate change.

Alpine plant communities differ in their seed germination requirements along a snowmelt gradient in the Caucasus

Mesoscale heterogeneity of alpine landscapes generates snowmelt gradients resulting in a distinct vegetation zonation from almost snow-free fellfields to long-lasting snowbeds. Although the vegetative trait variation along such gradients has been intensively studied, little is known about whether and how seed germination is adapted to the variable snowpack duration. Here, we compare the seed germination niches of 18 characteristic plant species occurring in four distinct plant communities (alpine lichen heath—Festuca varia grassland—Geranium-Hedysarum meadow—snowbed) along an alpine snowmelt gradient in the North Caucasus (Russia). In a fully factorial experiment, we tested seed germination responses to temperature (10/2, 14/6, 18/10, 22/14, 26/18 and 30/22 °C) and water potential (0, − 0.2, − 0.4, − 0.6 and − 0.8 MPa) gradients, reflecting the full spectrum of seedling establishment conditions in the study system. Community-specific germination niches were identified by generalised mixed model with Bayesian estimation. Our study revealed that the species from the four focal communities significantly differed in their temperature requirements for germination, whereas soil moisture was found to be a limiting factor for seedling establishment along the entire gradient. The snowbed germination was constrained to comparatively high temperatures above 10 °C, whereas seed germination in alpine lichen heaths occurred under a wide range of experimental conditions. The seed germination patterns of species from Festuca varia grasslands and Geranium-Hedysarum meadows reflected their intermediate position along the snowmelt gradient. We conclude that seed germination niche is affected by the environmental filtering along the snowmelt gradient thus departing from the general alpine germination syndrome.

Understanding the interplay of temperature and moisture on the germination niche to improve management of threatened species impacted by mining

The return of vegetation to mined lands often requires broadcast seeding of diverse native seed mixes. However, seeds are highly adapted to germination windows with specific hydrothermal thresholds that maximize the likelihood of seedling survival, and post‐mining landscapes typically offer markedly different hydrothermal conditions than pre‐disturbance ecosystems. According to niche theory, generalist species should exhibit broader hydrothermal performance niches than specialist taxa, which may influence the success of recruitment from seeds in post‐mining ecological restoration. To test this assumption, the impact of hydrothermal stress (incubation temperature (10–30°C) and osmotic potential (−0.8 to 0 MPa)) on the time to 50% germination (t50) and maximum germination (Gmax) was compared between two narrow‐range species of conservation concern (Acacia woodmaniorum and A. karina) restricted to mining‐impacted Banded Ironstone Formations (BIF) and three broadly distributed congenerics (A. assimilis, A. exocarpoides, and A. ramulosa). The hydrothermal germination niches of the study species were broadly congruent with hydrothermal conditions of their habitats. The two range‐restricted taxa were more tolerant of hydrothermal stress compared to the three widely distributed taxa, suggesting that tolerance of greater hydrothermal stress by both range‐restricted Acacia species is likely to be adaptive to establishment in uncontested niche space. Complex interactions between thermal and water stress suggest these environmental gradients may shape the germination niche as well as patterns of plant diversity in BIF ecosystems. This study highlights the importance of quantifying interactions between niche dimensions and their implications for species performance, which will aid future restoration efforts for micro‐endemic species impacted by mining.

Neuronal Polarity Pathways as Central Integrators of Cell-Extrinsic Information During Interactions of Neural Progenitors With Germinal Niches.

Germinal niche interactions and their effect on developing neurons have become the subject of intense investigation. Dissecting the complex interplay of cell-extrinsic and cell-intrinsic factors at the heart of these interactions reveals the critical basic mechanisms of neural development and how it goes awry in pediatric neurologic disorders. A full accounting of how developing neurons navigate their niches to mature and integrate into a developing neural circuit requires a combination of genetic characterization of and physical access to neurons and their supporting cell types plus transformative imaging to determine the cell biological and gene-regulatory responses to niche cues. The mouse cerebellar cortex is a prototypical experimental system meeting all of these criteria. The lessons learned therein have been scaled to other model systems and brain regions to stimulate discoveries of how developing neurons make many developmental decisions. This review focuses on how mouse cerebellar granule neuron progenitors interact with signals in their germinal niche and how that affects the neuronal differentiation and cell polarization programs that underpin lamination of the developing cerebellum. We show how modeling of these mechanisms in other systems has added to the growing evidence of how defective neuronal polarity contributes to developmental disease.

Climate shapes the seed germination niche of temperate flowering plants: a meta-analysis of European seed conservation data.

Interactions between ecological factors and seed physiological responses during the establishment phase shape the distribution of plants. Yet, our understanding of the functions and evolution of early-life traits has been limited by the scarcity of large-scale datasets. Here, we tested the hypothesis that the germination niche of temperate plants is shaped by their climatic requirements and phylogenetic relatedness, using germination data sourced from a comprehensive seed conservation database of the European flora (ENSCOBASE). We performed a phylogenetically informed Bayesian meta-analysis of primary data, considering 18 762 germination tests of 2418 species from laboratory experiments conducted across all European geographical regions. We tested for the interaction between species' climatic requirements and germination responses to experimental conditions including temperature, alternating temperature, light and dormancy-breaking treatments, while accounting for between-study variation related to seed sources and seed lot physiological status. Climate was a strong predictor of germination responses. In warm and seasonally dry climates the seed germination niche includes a cold-cued germination response and an inhibition determined by alternating temperature regimes and cold stratification, while in climates with high temperature seasonality opposite responses can be observed. Germination responses to scarification and light were related to seed mass but not to climate. We also found a significant phylogenetic signal in the response of seeds to experimental conditions, providing evidence that the germination niche is phylogenetically constrained. Nevertheless, phylogenetically distant lineages exhibited common germination responses under similar climates. This is the first quantitative meta-analysis of the germination niche at a continental scale. Our findings showed that the germination niches of European plants exhibit evolutionary convergence mediated by strong pressures at the macroclimatic level. In addition, our methodological approach highlighted how large datasets generated by conservation seed banking can be valuable sources to address questions in plant macroecology and evolution.

Seed size dimorphism in Hyptis suaveolens aids in differentiation of the germination niche.

Seed germination characteristics help predict the degree of invasive success of a species based on capacity of the seeds to germinate and recruit into novel habitats. Hyptis suaveolens (L.) Poit. (Bush mint, Pignut; Lamiaceae) is an invasive plant that is spreading throughout tropical and subtropical regions worldwide. We conducted a study to understand the role of seed size dimorphism in differentiation of germination niche in H. suaveolens. We subjected small and large seeds to varying environmental conditions of temperature (°C), photoperiod (light/dark), salt (NaCl; mM), pH, osmotic potential (MPa), different soil types and ratios (clay:sand) and burial depth (cm). Different germination indices were calculated and their interaction with seed dimorphism studied. There was a significant interaction (P < 0.001) between germination indices and seed dimorphism throughout the treatments. Large seeds had higher germination percentage and rate, indicating higher germination capacity. In addition, these displayed more asynchronous germination under various environments. Small seeds, on the other hand, required a longer germination time as compared to large seeds, indicating slower germination. Differential responses of the two seed morphs to varying environmental conditions, therefore, help H. suaveolens to differentiate its germination niche and establish in heterogeneous environments. These findings will help in devising appropriate management and eradication strategies based on germination ecology of seeds.

GLI3 Is Required for OLIG2+ Progeny Production in Adult Dorsal Neural Stem Cells.

The ventricular–subventricular zone (V-SVZ) is a postnatal germinal niche. It holds a large population of neural stem cells (NSCs) that generate neurons and oligodendrocytes for the olfactory bulb and (primarily) the corpus callosum, respectively. These NSCs are heterogeneous and generate different types of neurons depending on their location. Positional identity among NSCs is thought to be controlled in part by intrinsic pathways. However, extrinsic cell signaling through the secreted ligand Sonic hedgehog (Shh) is essential for neurogenesis in both the dorsal and ventral V-SVZ. Here we used a genetic approach to investigate the role of the transcription factors GLI2 and GLI3 in the proliferation and cell fate of dorsal and ventral V-SVZ NSCs. We find that while GLI3 is expressed in stem cell cultures from both dorsal and ventral V-SVZ, the repressor form of GLI3 is more abundant in dorsal V-SVZ. Despite this high dorsal expression and the requirement for other Shh pathway members, GLI3 loss affects the generation of ventrally-, but not dorsally-derived olfactory interneurons in vivo and does not affect trilineage differentiation in vitro. However, loss of GLI3 in the adult dorsal V-SVZ in vivo results in decreased numbers of OLIG2-expressing progeny, indicating a role in gliogenesis.

The sweet and musky scent of home: biogenic ethylene fine-tunes seed germination in wetlands.

Wetlands are known for comparatively high production of biogenic ethylene from decomposed sediment. Because the gas has various well-documented effects on seed physiology, we asked whether it can be a vital seed germination cue for wetland plants. Specifically, we explored whether ethylene plays an ecological role in (i) breaking/weakening seed dormancy, (ii) broadening the germination niche width, (iii) promoting germination speed or (iv) altering the germination requirements of six plant species with different occurrence along a hydroperiod gradient. In a factorial experiment, both ethylene-treated and untreated seeds were incubated in combinations of temperature (constant versus fluctuating), illumination (light versus darkness) and oxygen (aerobic versus hypoxia) with and without cold stratification. Our results revealed seed exposure to ethylene did not weaken or break dormancy without cold stratification treatment. However, ethylene helped to broaden the germination niche width, increased overall germination percentage and speed of cold-stratified (non-dormant) seeds. This indicates that ethylene helps those seeds that lost dormancy (non-dormant) to sense favourable water-saturated versus flooded substrate depending on their requirement for aerobic versus hypoxic conditions to trigger germination. We conclude that ethylene does not interfere directly with the dormancy-breaking process in autumn-dispersed seeds that are naturally cold-stratified in winter and germinate in spring/summer. However, ethylene plays a crucial ecological role as a 'flood detector' for different wetland plant communities (reed, mudflat, swamp, shallow water) to synchronize germination of non-dormant seeds in the most suitable habitat at the right time.

Optimising conservation translocations of threatened

Context Conservation translocations are increasingly being used in the management of rare plants, yet have low success in maintaining populations through recruitment. Aims We investigated whether the survival of translocated plants, recruitment and, therefore, cost effectiveness, can be improved by selecting optimal microsites for both adults and seedlings. Methods Caladenia colorata plants propagated symbiotically with Serendipita australiana (n = 735) were introduced to four sites where the pollinator was present and vegetation matched wild populations. Plant demography was monitored over 6 years. The relationship between microsite variables and measures of orchid survival, re-emergence, flowering and recruitment were analysed with generalised linear mixed-effects models. We then estimated potential improvement in emergence and recruitment, if microsite selection was optimised. Key results A total of 77% of plants survived translocation, and populations grew by 84% through recruitment (n = 615). Survival was positively associated with cover of leaf litter, graminoids and cryptogams. Recruitment was positively correlated with soil moisture. The majority of recruitment was within 5 cm of adult C. colorata plants. The potential improvement by selecting favourable microsites increased adult survival by up to 8% and recruitment by 10–40%. Conclusions Incorporating both the germination niche and adult plant niche within plant translocations more broadly could significantly improve long-term population persistence and the utilisation of conservation funding. Implications Our results are directly applicable to 58 endangered Caladenia species in the subgenus Calonema, owing to their shared mycorrhizal association with S. australiana. Furthermore, our results are applicable to all plant translocations as understanding germination niche and microhabitat requirements is likely to improve success overall.

Many roads to success: different combinations of life‐history traits provide accurate germination timing in seasonally dry environments

Germination timing is determined by several plant life‐history traits. Seed dormancy regulates the time and place of early plant development and spreads recruitment risks over time. Dispersal phenology and syndrome can influence germination timing and buffer spatial heterogeneity. The ecological requirements for germination (the germination niche) can also influence when and where germination takes place. To date, the relative importance of each of these four traits to ensure the phenological adaptation of individual species in diverse communities remains unexplored. Here, we investigated the functional interactions among them and their relevance in heterogenous, seasonally dry environments.We collected seed dispersal phenology and syndrome for 82 species of the Brazilian savanna (cerrado) and evaluated the dormancy and germination behavior of the seeds of every taxon. Based on these data, we developed two new ecological indexes to estimate the likelihood of a non‐dormant seed to germinate upon dispersal (∆G) and the overall variability of germination through time (σT). We then evaluated the influence of each trait on germination timing within a phylogenetically controlled framework.Our results show that even though germination is concentrated at the beginning of the rainy season, seed dispersal takes place year‐round. Non‐dormant seeds released during the dry season were characterized by high ∆G values that delayed their germination until the onset of the favorable season. Simultaneously, seed dormancy and spatial dispersal (i.e., the two risk‐reduction mechanisms) were negatively correlated as dormancy and high σT values were only prevalent in seeds with reduced spatial dispersal ability. We conclude that the timing of seed germination is ultimately the net outcome of adaptive interactions among life‐history traits, which can result in multiple functionally equivalent phenotypes. It is possible that this might contribute to community diversity by providing opportunities for the coexistence of different species.

Advancing Our Understanding of Brain Disorders: Research Using Postmortem Brain Tissue.

It is thought that proliferative potential of neural progenitor cells, from postmortem tissue obtained from idiopathic PD patients, present in the substantia nigra (SN) as well as other brain regions can be maintained in vitro. While they might be lacking in factors required for differentiation into mature neurons, their regenerative potential is undeniable and suggestive that progenitor cells are found endogenously in the diseased brain. Adult stem/progenitor cells exist in several regions within the PD brain and are likely a valuable source of progenitor cells for understanding disease course, as well as useful tools for generating potential cellular and pharmacologic therapies. One successful therapy for some PD patients is deep brain stimulation (DBS) and has been used for more than a decade to treat PD; however its mechanism of action remains unknown. Given the close proximity of the electrode trajectory to areas of the brain known as the "germinal niches" and the Parkinsonian brain's regenerative potential, it is possible that DBS influences neural stem cell proliferation locally, as well as distally. A study of banked brain tissue from idiopathic PD patients treated with DBS, compared to 12 control brains without CNS disease, identified a significant increase in the number of proliferating precursor cells in the subventricular zone (SVZ) of the lateral ventricles, the third ventricle, and the tissue surrounding the DBS lead. Our studies with banked human tissues from the aforementioned regions demonstrate the importance of studying brain-banked tissue from germinal niches and DBS perielectrode tissue. We reveal in these studies the presence of proliferative potential in diseased brains as well as an increase in cellular plasticity in the brain as a consequence of DBS.

A quantitative analysis of primary dormancy and dormancy changes during burial in seeds of Brassica napus

For plants inhabiting unpredictable environments, scheduling germination can be challenging. Various responses to environmental conditions have been evolved by plants; these responses combine with variation in local climate to construct germination niche. Germination process may be regulated by a number of factors, among them, the type of seed dormancy and dormancy cycling play an important role in promoting survival after dispersal. In the present study, seeds of Brassica napus were tested for primary conditional dormancy (CD). Dormancy changes were quantified through seed population thermal germination parameters to test whether different genotypes of B. napus seeds (944, 966, Alestrom, Danube, Okanto and Rohan) are non‐dormant (ND) at the maturity or if they present primary dormancy (D or CD). In a burial experiment, B. napus seeds dormancy cycling in the natural soil seedbank was investigated. Germination of all genotypes decreased at 5 and &gt; 20°C, showing narrower breadth of thermal niche for germination. Dormancy‐breaking treatments lead to the widening of thermal range permissive for germination. The lower limit (Tl(50)) and higher limit (Th(50)) temperatures for germination decreased and increased, respectively, for non‐dormant (after‐ripened seeds treated with GA3) seeds compared with fresh seeds in all genotypes. In fresh seeds, the Tl(50) and Th(50) for various genotypes ranged from 3.61 to 6.5°C and 25.0 to 29.0°C, respectively and ranged from 0.2 to 1.8°C and 35 to 41.0°C in non‐dormant seeds. Thus, fresh seeds of B. napus are dormant at dispersal and adopt delayed germination strategies to avoid summer drought. In the burial experiment, the results indicated that B. napus must have D/ND cycle in which fresh seeds first become dormant and then the cycle begins (CD→D↔CD↔ND), thus adopting both risk‐prone and risk‐adverse strategies to spread the likelihood of survival over time.

Plant reproductive traits in old and recently-restored temperate forest understories

Recently-restored forests on former agricultural land have impoverished herbaceous understories. This is partly due to the poor colonizing capacity of understory plants, which makes them slow in responding to land use change. Functional traits can be used to compare old and recent understories and provide insight about which plant syndromes are missing after restoration intervention. In this work, we focus on the seed and germination traits of herbaceous understories, investigating how they influence community assembly in restored woodlands.We studied temperate deciduous oak forests in two locations at the centre and southern limit of the European Atlantic region (Loder Valley Nature Reserve, England; and Tragamón Oak Grove, Spain). In each location, we sampled a pair of old and recently-restored forest sites and established 10 permanent plots, where we surveyed understory species abundances every two months for one year. We recorded plant reproductive traits for the species found and measured germination traits in laboratory experiments with seeds collected in situ. Finally, we calculated community-weighted means (CWM) for each trait and plot.The reproductive traits of old and recent forest understory species had significant differences in both locations. Old forest communities had shorter plants that flowered earlier and were more dependent on vegetative reproduction. They produced less seeds, which were heavier and had higher terminal velocity. The germination of these seeds occurred at colder temperatures and was less dependent on light. However, some dormancy-related traits seem more related to bioclimatic differences between the two locations (England and Spain).Old and recently-restored communities vary consistently for several reproductive traits, with old community traits reflecting a poor dispersal capacity and a specialized germination niche in shaded habitats under a deciduous canopy. When designing species mixes for restoration efforts, plants with particular old understory traits should be given priority.