Special Issue "Linking Seed Biology to Plant Preservation: New Advances and Perspectives"

A special issue of Plants (ISSN 2223-7747).

Deadline for manuscript submissions: closed (30 September 2020).

Special Issue Editor

Dr. Héctor E. Pérez
E-Mail Website
Guest Editor
Department of Environmental Horticulture, University of Florida, USA
Interests: Seed Biology

Special Issue Information

Dear Colleagues,

We are living in an unprecedented time of plant biodiversity loss. Present estimates suggest that 30% of plant species are threatened with extinction. Moreover, current rates of extinction are three-orders of magnitude faster than extinction rates measured over geologic time. These two pieces of information should be astonishing to anyone given humanity’s dependence on plants for survival. However, we are not solely losing plants in danger of extinction. We are losing crop wild relatives that contain important genetic information. We are losing plants that serve as sources of medicines, foods, and fibers. We are losing undiscovered species that form important networks and provide valuable ecological services. Fortunately, several systems exist to preserve plant genetic diversity and give species a chance at winning in the biodiversity loss crisis. These systems span a continuum from preserving plants in their natural habitat to storage within genebanks.

Seeds form the foundation for these systems. For example, practitioners may focus on promoting the formation of soil seed banks for species in the wild. Alternatively, managers may strive to preserve all or most of the genetic diversity of a target plant using a seed genebank. Therefore, intimate knowledge of seed biology is imperative regardless of the preservation system. Recent advances provide clarity on the germination ecology of many species and the relationship of this to plant preservation in the field. Similarly, new research reveals some of the biochemical, biophysical, genetic, and physiological aspects underpinning the ability of seeds to tolerate (or be sensitive to) stresses, such as desiccation or aging, that are required for or result from storage of seeds in genebanks. Nevertheless, despite this considerable progress, we require novel seed biology insights as we work towards creating a unifying plant preservation framework. Many open questions exist, for example: How will a changing climate influence dormancy and germination dynamics for seeds in the wild or seeds placed again in the wild after storage? Why do seeds of different species vary in their ability to tolerate imposed or induced stresses associated with preservation? And can we identify seed traits that enhance our ability to preserve plant species? The aim of this Special Issue is to join papers providing new findings and views related to the biochemistry, biophysics, ecology, genetics, and physiology of seed biology with the potential to enhance plant preservation.

Dr. Héctor E. Pérez
Guest Editor

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Keywords

  • abiotic stress
  • conservation
  • dormancy
  • ecophysiology
  • ex situ
  • germination
  • germplasm
  • in situ
  • seed development
  • seed functional traits
  • seed quality

Published Papers (12 papers)

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Research

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Article
Seed Morphology in Silene Based on Geometric Models
Plants 2020, 9(12), 1787; https://doi.org/10.3390/plants9121787 - 16 Dec 2020
Cited by 4 | Viewed by 1235
Abstract
Seed description in morphology is often based on adjectives such as “spherical”, “globular”, or “reniform”, but this does not provide a quantitative method. A new morphological approach based on the comparison of seed images with geometric models provides a seed description in Silene [...] Read more.
Seed description in morphology is often based on adjectives such as “spherical”, “globular”, or “reniform”, but this does not provide a quantitative method. A new morphological approach based on the comparison of seed images with geometric models provides a seed description in Silene species on a quantitative basis. The novelty of the proposed method is based in the comparison of the seed images with geometric models according to a cardioid shape. The J index is a measurement that indicates the seed percentage of similarity with a cardioid or cardioid-derived figures used as models. The seeds of Silene species have high values of similarity with the cardioid and cardioid-derived models (J index superior to 90). The comparison with different figures allows species description and differentiation. The method is applied here to seeds of 21 species and models are proposed for some of them including S. diclinis, an endangered species. The method is discussed in the context of previous comparison with the measures used in traditional morphometric analysis. The similarity of seed images with geometric figures opens a new perspective for the automatized taxonomical evaluation of samples linking seed morphology to functional traits in endangered Silene species. Full article
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Article
Analysis of Stored mRNA Degradation in Acceleratedly Aged Seeds of Wheat and Canola in Comparison to Arabidopsis
Plants 2020, 9(12), 1707; https://doi.org/10.3390/plants9121707 - 04 Dec 2020
Viewed by 475
Abstract
Seed aging has become a topic of renewed interest but its mechanism remains poorly understood. Our recent analysis of stored mRNA degradation in aged Arabidopsis seeds found that the stored mRNA degradation rates (estimated as the frequency of breakdown per nucleotide per day [...] Read more.
Seed aging has become a topic of renewed interest but its mechanism remains poorly understood. Our recent analysis of stored mRNA degradation in aged Arabidopsis seeds found that the stored mRNA degradation rates (estimated as the frequency of breakdown per nucleotide per day or β value) were constant over aging time under stable conditions. However, little is known about the generality of this finding to other plant species. We expanded the analysis to aged seeds of wheat (Triticum aestivum) and canola (Brassica napus). It was found that wheat and canola seeds required much longer periods than Arabidopsis seeds to lose seed germination ability completely under the same aging conditions. As what had been observed for Arabidopsis, stored mRNA degradation (∆Ct value in qPCR) in wheat and canola seeds correlated linearly and tightly with seed aging time or mRNA fragment size, while the quality of total RNA showed little change during seed aging. The generated β values reflecting the rate of stored mRNA degradation in wheat or canola seeds were similar for different stored mRNAs assayed and constant over seed aging time. The overall β values for aged seeds of wheat and canola showed non-significant differences from that of Arabidopsis when aged under the same conditions. These results are significant, allowing for better understanding of controlled seed aging for different species at the molecular level and for exploring the potential of stored mRNAs as seed aging biomarkers. Full article
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Article
Flash Flaming Improves Flow Properties of Mediterranean Grasses Used for Direct Seeding
Plants 2020, 9(12), 1699; https://doi.org/10.3390/plants9121699 - 03 Dec 2020
Viewed by 469
Abstract
The demand for native grasses is increasing in restoration and agriculture, though their use is often limited due to seed handling challenges. The external structures surrounding the grass seed (i.e., the floret) possess hairs, awns, and appendages which create blockages in conventional seeding [...] Read more.
The demand for native grasses is increasing in restoration and agriculture, though their use is often limited due to seed handling challenges. The external structures surrounding the grass seed (i.e., the floret) possess hairs, awns, and appendages which create blockages in conventional seeding equipment. Flash flaming is a patented technology which allows precision exposure of floret material to flames to singe off hairs and appendages. We used two grasses native to Mediterranean ecosystems of Western Australia (Amphipogon turbinatus R.Br. and Neurachne alopecuoidea R.Br.) to evaluate the effects of different flaming techniques on flow properties and germination. Flaming significantly improved flowability in both species and had both neutral (A. turbinatus) and negative (N. alopecuroidea) effects on germination. Flaming torch size influenced germination, though flaming temperature (low or high) and whether this was kept constant or alternating had no effect. The best evaluation of germination following flaming was achieved by cleaning flamed florets to seed and/or germinating in the presence of karrikinolide (KAR1) or gibberellic acid (GA3). We suggest that flaming settings (particularly torch size) require species-specific evaluation and optimisation. Removing seeds from flamed florets and germination testing this material in the presence of stimulants may be a useful protocol for future flaming evaluations. Full article
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Article
Enhancing Conservation of a Globally Imperiled Rockland Herb (Linum arenicola) through Assessments of Seed Functional Traits and Multi-Dimensional Germination Niche Breadths
Plants 2020, 9(11), 1493; https://doi.org/10.3390/plants9111493 - 05 Nov 2020
Viewed by 501
Abstract
Humans currently face an extraordinary period of plant biodiversity loss. One strategy to stem further losses involves the development of species-level recovery plans that guide conservation actions. Seeds represent an important component in the life history of plants and are crucial for conservation [...] Read more.
Humans currently face an extraordinary period of plant biodiversity loss. One strategy to stem further losses involves the development of species-level recovery plans that guide conservation actions. Seeds represent an important component in the life history of plants and are crucial for conservation activities. Yet, most recovery plans contain meager seed biology information. We set out to examine seed functional traits and germination niche breadth of Linum arenicola seeds exposed to a range of thermal, photoperiodic, and salinity gradients to gain perspectives on the seed biology of this endangered species that may inform conservation decision making and assist recovery plan development. We found that fresh seeds possess non-deep physiological dormancy, which may be alleviated via a four-week dry after-ripening treatment. The germination response of non-dormant seeds is subsequently promoted by constant rather than alternating temperatures. The optimum germination temperature range is 20–22 °C. Non-dormant seeds do not possess an absolute light requirement for germination, but are sensitive to low levels of salinity (EC50 = 6.34 ppth NaCl). The narrow thermal and salinity germination niche breadths reported here suggest a specialized reproductive strategy that may require careful consideration when planning ex and in situ conservation activities. Full article
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Communication
Variation in Seed Metabolites between Two Indica Rice Accessions Differing in Seed Longevity
Plants 2020, 9(9), 1237; https://doi.org/10.3390/plants9091237 - 19 Sep 2020
Viewed by 852
Abstract
For a better understanding of germination after seed storage, metabolite profiling was conducted using hybrid triple quadrupole time-of-flight (QTOF) mass spectrometry. After moisture content (MC) equilibration, seeds of “WAS170” (short-lived) and “IR65483” (long-lived) were stored at 10.9% MC and 45 °C. Samples for [...] Read more.
For a better understanding of germination after seed storage, metabolite profiling was conducted using hybrid triple quadrupole time-of-flight (QTOF) mass spectrometry. After moisture content (MC) equilibration, seeds of “WAS170” (short-lived) and “IR65483” (long-lived) were stored at 10.9% MC and 45 °C. Samples for metabolite analysis were taken after 0 and 20 days of storage. Among 288 metabolites, two flavonoids (kaempferide and quercetin-3-arabinoside), one amino acid (S-sulfocysteine) and one sugar (D-glucose) increased in “IR65483” seeds after storage but were not detected in “WAS170” seeds. Based on the genome sequence database, we identified clear allelic differences with non-synonymous mutations on the six flavonol synthase genes regulating the accumulation of kaempferol- and quercetin-metabolites. On the other hand, two metabolites (thiamine monophosphate and harmaline) increased in short-lived seeds after storage; these metabolites could be potential biochemical indicators of seed deterioration. Full article
Article
Simulated Photovoltaic Solar Panels Alter the Seed Bank Survival of Two Desert Annual Plant Species
Plants 2020, 9(9), 1125; https://doi.org/10.3390/plants9091125 - 31 Aug 2020
Cited by 2 | Viewed by 829
Abstract
Seed bank survival underpins plant population persistence but studies on seed bank trait-environment interactions are few. Changes in environmental conditions relevant to seed banks occur in desert ecosystems owing to solar energy development. We developed a conceptual model of seed bank survival to [...] Read more.
Seed bank survival underpins plant population persistence but studies on seed bank trait-environment interactions are few. Changes in environmental conditions relevant to seed banks occur in desert ecosystems owing to solar energy development. We developed a conceptual model of seed bank survival to complement methodologies using in-situ seed bank packets. Using this framework, we quantified the seed bank survival of two closely related annual desert plant species, one rare (Eriophyllum mohavense) and one common (Eriophyllum wallacei), and the seed bank–environment interactions of these two species in the Mojave Desert within a system that emulates microhabitat variation associated with solar energy development. We tracked 4860 seeds buried across 540 seed packets and found, averaged across both species, that seed bank survival was 21% and 6% for the first and second growing seasons, respectively. After two growing seasons, the rare annual had a significantly greater seed bank survival (10%) than the common annual (2%). Seed bank survival across both species was significantly greater in shade (10%) microhabitats compared to runoff (5%) and control microhabitats (3%). Our study proffers insight into this early life-stage across rare and common congeners and their environmental interactions using a novel conceptual framework for seed bank survival. Full article
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Article
Thermal Requirements Underpinning Germination Allude to Risk of Species Decline from Climate Warming
Plants 2020, 9(6), 796; https://doi.org/10.3390/plants9060796 - 25 Jun 2020
Cited by 5 | Viewed by 881
Abstract
The storage of seeds is a commonly used means of preserving plant genetic diversity in the face of rising threats such as climate change. Here, the findings of research from the past decade into thermal requirements for germination are synthesised for more than [...] Read more.
The storage of seeds is a commonly used means of preserving plant genetic diversity in the face of rising threats such as climate change. Here, the findings of research from the past decade into thermal requirements for germination are synthesised for more than 100 plant species from southern Western Australia. This global biodiversity hotspot is predicted to suffer major plant collapse under forecast climate change. A temperature gradient plate was used to assess the thermal requirements underpinning seed germination in both commonly occurring and geographically restricted species. The results suggest that the local climate of the seed source sites does not drive seed responses, neither is it indicative of temperatures for optimal germination. The low diurnal phase of the temperature regime provided the most significant impact on germination timing. Several species germinated optimally at mean temperatures below or close to current wet quarter temperatures, and more than 40% of species were likely to be impacted in the future, with germination occurring under supra-optimal temperature conditions. This research highlights both species vulnerability and resilience to a warming climate during the regeneration phase of the life cycle and provides vital information for those aiming to manage, conserve and restore this regional flora. Full article
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Article
Comparative Seed Morphology of Tropical and Temperate Orchid Species with Different Growth Habits
Plants 2020, 9(2), 161; https://doi.org/10.3390/plants9020161 - 29 Jan 2020
Cited by 4 | Viewed by 1716
Abstract
Seed morphology underpins many critical biological and ecological processes, such as seed dormancy and germination, dispersal, and persistence. It is also a valuable taxonomic trait that can provide information about plant evolution and adaptations to different ecological niches. This study characterised and compared [...] Read more.
Seed morphology underpins many critical biological and ecological processes, such as seed dormancy and germination, dispersal, and persistence. It is also a valuable taxonomic trait that can provide information about plant evolution and adaptations to different ecological niches. This study characterised and compared various seed morphological traits, i.e., seed and pod shape, seed colour and size, embryo size, and air volume for six orchid species; and explored whether taxonomy, biogeographical origin, or growth habit are important determinants of seed morphology. We investigated this on two tropical epiphytic orchid species from Indonesia (Dendrobium strebloceras and D. lineale), and four temperate species from New Zealand, terrestrial Gastrodia cunnninghamii, Pterostylis banksii and Thelymitra nervosa, and epiphytic D. cunninghamii. Our results show some similarities among related species in their pod shape and colour, and seed colouration. All the species studied have scobiform or fusiform seeds and prolate-spheroid embryos. Specifically, D. strebloceras, G. cunninghamii, and P. banksii have an elongated seed shape, while T. nervosa has truncated seeds. Interestingly, we observed high variability in the micro-morphological seed characteristics of these orchid species, unrelated to their taxonomy, biogeographical origin, or growth habit, suggesting different ecological adaptations possibly reflecting their modes of dispersal. Full article
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Article
Lipid Thermal Fingerprints of Long-term Stored Seeds of Brassicaceae
Plants 2019, 8(10), 414; https://doi.org/10.3390/plants8100414 - 14 Oct 2019
Cited by 5 | Viewed by 1126
Abstract
Thermal fingerprints for seeds of 20 crop wild relatives of Brassicaceae stored for 8 to 44 years at the Plant Germplasm Bank—Universidad Politécnica de Madrid and the Royal Botanic Gardens, Kew’s Millennium Seed Bank—were generated using differential scanning calorimetry (DSC) and analyzed in [...] Read more.
Thermal fingerprints for seeds of 20 crop wild relatives of Brassicaceae stored for 8 to 44 years at the Plant Germplasm Bank—Universidad Politécnica de Madrid and the Royal Botanic Gardens, Kew’s Millennium Seed Bank—were generated using differential scanning calorimetry (DSC) and analyzed in relation to storage stability. Relatively poor storing oily seeds at −20 °C tended to have lipids with crystallization and melting transitions spread over a wide temperature range (c. 40 °C) that spanned the storage temperature, plus a melting end temperature of around 15 °C. We postulated that in dry storage, the variable longevity in Brassicaceae seeds could be associated with the presence of a metastable lipid phase at the temperature at which they are being stored. Consistent with that, when high-quality seed samples of various species were assessed after banking at −5 to −10 °C for c. 40 years, melting end temperatures were observed to be much lower (c. 0 to −30 °C) and multiple lipid phases did not occur at the storage temperature. We conclude that multiple features of the seed lipid thermal fingerprint could be used as biophysical markers to predict potential poor performance of oily seeds during long-term, decadal storage. Full article
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Review

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Review
In Vitro Symbiotic Germination: A Revitalized Heuristic Approach for Orchid Species Conservation
Plants 2020, 9(12), 1742; https://doi.org/10.3390/plants9121742 - 09 Dec 2020
Viewed by 1001
Abstract
As one of the largest families of flowering plants, Orchidaceae is well-known for its high diversity and complex life cycles. Interestingly, such exquisite plants originate from minute seeds, going through challenges to germinate and establish in nature. Alternatively, orchid utilization as an economically [...] Read more.
As one of the largest families of flowering plants, Orchidaceae is well-known for its high diversity and complex life cycles. Interestingly, such exquisite plants originate from minute seeds, going through challenges to germinate and establish in nature. Alternatively, orchid utilization as an economically important plant gradually decreases its natural population, therefore, driving the need for conservation. As with any conservation attempts, broad knowledge is required, including the species’ interaction with other organisms. All orchids establish mycorrhizal symbiosis with certain lineages of fungi to germinate naturally. Since the whole in situ study is considerably complex, in vitro symbiotic germination study is a promising alternative. It serves as a tool for extensive studies at morphophysiological and molecular levels. In addition, it provides insights before reintroduction into its natural habitat. Here we reviewed how mycorrhiza contributes to orchid lifecycles, methods to conduct in vitro study, and how it can be utilized for conservation needs. Full article
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Review
Late Embryogenesis Abundant Protein–Client Protein Interactions
Plants 2020, 9(7), 814; https://doi.org/10.3390/plants9070814 - 29 Jun 2020
Cited by 1 | Viewed by 1170
Abstract
The intrinsically disordered proteins belonging to the LATE EMBRYOGENESIS ABUNDANT protein (LEAP) family have been ascribed a protective function over an array of intracellular components. We focus on how LEAPs may protect a stress-susceptible proteome. These examples include instances of LEAPs providing a [...] Read more.
The intrinsically disordered proteins belonging to the LATE EMBRYOGENESIS ABUNDANT protein (LEAP) family have been ascribed a protective function over an array of intracellular components. We focus on how LEAPs may protect a stress-susceptible proteome. These examples include instances of LEAPs providing a shield molecule function, possibly by instigating liquid-liquid phase separations. Some LEAPs bind directly to their client proteins, exerting a holdase-type chaperonin function. Finally, instances of LEAP–client protein interactions have been documented, where the LEAP modulates (interferes with) the function of the client protein, acting as a surreptitious rheostat of cellular homeostasis. From the examples identified to date, it is apparent that client protein modulation also serves to mitigate stress. While some LEAPs can physically bind and protect client proteins, some apparently bind to assist the degradation of the client proteins with which they associate. Documented instances of LEAP–client protein binding, even in the absence of stress, brings to the fore the necessity of identifying how the LEAPs are degraded post-stress to render them innocuous, a first step in understanding how the cell regulates their abundance. Full article
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Review
Breaking Seed Dormancy during Dry Storage: A Useful Tool or Major Problem for Successful Restoration via Direct Seeding?
Plants 2020, 9(5), 636; https://doi.org/10.3390/plants9050636 - 16 May 2020
Cited by 11 | Viewed by 1814
Abstract
To facilitate the restoration of disturbed vegetation, seeds of wild species are collected and held in dry storage, but often there is a shortage of seeds for this purpose. Thus, much research effort is expended to maximize the use of the available seeds [...] Read more.
To facilitate the restoration of disturbed vegetation, seeds of wild species are collected and held in dry storage, but often there is a shortage of seeds for this purpose. Thus, much research effort is expended to maximize the use of the available seeds and to ensure that they are nondormant when sown. Sowing nondormant (versus dormant) seeds in the field should increase the success of the restoration. Of the various treatments available to break seed dormancy, afterripening, that is, dormancy break during dry storage, is the most cost-effective. Seeds that can undergo afterripening have nondeep physiological dormancy, and this includes members of common families such as Asteraceae and Poaceae. In this review, we consider differences between species in terms of seed moisture content, temperature and time required for afterripening and discuss the conditions in which afterripening is rapid but could lead to seed aging and death if storage is too long. Attention is given to the induction of secondary dormancy in seeds that have become nondormant via afterripening and to the biochemical and molecular changes occurring in seeds during dry storage. Some recommendations are made for managing afterripening so that seeds are nondormant at the time for sowing. The most important recommendation probably is that germination responses of the seeds need to be monitored for germinability/viability during the storage period. Full article
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