Storing seeds allows for the long-term preservation of genetic diversity that can ensure crop viability in the case of natural disasters. Further research into the current limitations and future implications of seed storage, particularly the refinement of existing techniques and the eco-evolutionary impacts, will contribute to the improvement of seed storing practices.
Exploring the Arctic's Global Seed Vault
Values of seed storage in contemporary food science
The storage of seeds is a longstanding agricultural practice encompassing a diverse array of techniques. From traditional methods of seed storage to industrial seed banks, seed storage relies on controlled environmental conditions to prolong the viability of seeds. In today’s agricultural industry, seed banks are the most widely used method of seed storage.
Seed banks typically refer to vaults containing seeds preserved from different plant species ranging from economically valuable crops to ecologically important endangered plants. These vaults are protected from natural disasters as well as other potential threats such as radiation or explosives. Among other functions, these banks primarily store seeds to preserve the genetic diversity of plant species and are therefore a type of gene bank.
Conditions in a seed bank are generally low in humidity and temperature, with conditions around -20°C to ensure seeds can grow when needed at a future date. Around the world, over 1,000 such seed bank facilities exist, with the largest being the Millennium Seed Bank in Sussex, United Kingdom, which contains around 40,000 species of plants.
The use of seed banks has been documented throughout human history, with reports of seeds found in Egyptian pyramids and palaces. However, the true longevity of seed storage itself remains to be determined, with the longest current seed storage lasting 150 years in vaults.
Until the first vaults reach 1,000 years old or more, the health and re-use of seeds kept in seed banks have only been examined in food science, which has identified several challenges limiting the potential success and efficacy of seed banks.
Challenges to the use of traditional seed storage in relation to food security
Although research has focused on larger-scale seed banks, the most common practices of seed storage remain those used by smaller communities in remote regions that have been culturally inherited. Traditional practices of seed storage are rarely considered, but provide key insights into ways to improve existing strategies.
To find out what can be learned from traditional practices of seed storage, Rashid et al, reviewed the effects of different storage types on seeds in Bangladesh, a country with a burgeoning agricultural industry.
Authors found that improper storage practices led to increased moisture absorbance favoring the growth of pests and diseases, insect infestation, and fungal infection, ultimately deteriorating seed quality and viability. Results from the review found that the risk of these issues differed across storage types.
Traditionally, 4 containers are used including a gunny bag lined with polythene, bamboo bin lined with polythene, gunny bag, and earthen pot locally called matka. Researchers found each material had different moisture-retaining properties, in turn affecting seed health, with the lowest moisture, as well as best germination, found in the gunny bag lined with polythene.
Another difficulty with the long-term storage of seeds is the requirement of acquiring species-specific knowledge. To date, seeds are preserved cryogenically in an indiscriminate manner in larger facilities.
Although this benefits most plants as the colder temperature and humidity will maintain seed viability, traditional methods generally do not incorporate such conditions. Nonetheless, plants such as onion seeds require moisture content of no more than 6 ± 1% stored in moisture impervious containers at 4-15°C and 40 -60% relative humidity in order to be stored for over a year without suffering seed damage.
This was found by Selvi and Saraswathy in 2017, who also discussed how strategies of hydration-dehydration would significantly help in delaying the seed deteriorative processes and, thereby, increase the viability and longevity of seeds during storage. Such practices can be considered within traditional practices that do not have access to more controlled conditions.
Considering the benefits of seed storage and seed banks, therefore, requires careful attention to both large industrial storage as well as more traditional methods, which outnumber the latter particularly in regions where they rely more on seed storage. Incorporating various practices could also benefit seed viability, but species-specific knowledge remains an important factor for food science.
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Eco-evolutionary implications of seed banks and their effect on species conservation and food security
Ensuring future genetic diversity is not the only function of seeds as they also serve as a “memory” of the former vegetation within ecosystems. Therefore, seeds also act as reservoirs for biodiversity, which can be used during active restoration measures to replenish plant communities. Target species affected by habitat degradation can therefore be better preserved for future conservation plans.
This was documented by Kiss et al. in 2018 when they reviewed field and experimental seed bank studies and their role in buffering against climate change. Authors found that seed banks provided a restoration potential buffering against first-order (temperature and precipitation changes) and second-order effects of climate change (flooding and fire).
Further benefits were shown by Ludewig et al., 2020 who examined the restoration of a mountain meadow community using seed banks following the invasion by a non-native plant. This invasion altered the structure and composition of the meadow, and authors found high germination rates among threatened plants following storage translating into better restoration measures. The authors, therefore, argue that the seed bank offers potential for the active restoration of species-rich mountain meadows.
Beyond ecological implications, seed banks allow for long-term preservation of genetic diversity which affects the evolutionary trajectory of such plants and their associated species due to the extensive temporal scales involved.
The effect of dormancy on seeds was considered by Shoemaker and Lennon, 2017, who examined how seed banks affect macroevolutionary processes, including rates of speciation and extinction.
The authors found that seed banks preserve genetic and phenotypic diversity by stratifying populations. In a population with a seed bank, there are active and dormant subpopulations, where individuals enter and exit a dormant state in a manner analogous to migration between subpopulations. The nature and strength of evolutionary drivers such as migration, genetic drift, mutation rates, and gene flow, are then altered by dormancy, which requires key consideration when preserving seeds meant for restoration measures.
Seed banks, therefore, provide a number of benefits to ensure future food security as well as a candidate strategy for active restoration. However, knowledge gaps in our understanding of seed banks require consideration. Specifically, the role and vulnerabilities of smaller-scale traditional measures remain limited as well as our understanding of evolutionary forces at play during seed dormancy.
Nevertheless, seed banks offer a failproof strategy in a rapidly changing world, and improving existing measures of seed storage will be key to ensuring future food safety and security.
- Kiss, R., Deák, B., Török, P., Tóthmérész, B., & Valkó, O. (2018). Grassland seed bank and community resilience in a changing climate. Restoration Ecology, 26, S141–S150. https://doi.org/10.1111/rec.12694
- Ludewig, K., Hansen, W., Klinger, Y. P., Eckstein, R. L., & Otte, A. (2020). Seed bank offers potential for active restoration of mountain meadows. Restoration Ecology, 29(1). https://doi.org/10.1111/rec.13311
- Rashid, M., Hossain, I., Hassan, K., & Mondal, F. (2017). How Does Storing Containers on Farmers Stored Boro Rice Seed Affect the Seed Qualities? Universal Journal of Plant Science, 5(4), 45–48. https://doi.org/10.13189/ujps.2017.050401
- Shoemaker, W. R., & Lennon, J. T. (2018). Evolution with a seed bank: The population genetic consequences of microbial dormancy. Evolutionary Applications, 11(1), 60–75. https://doi.org/10.1111/eva.12557
- Thirusendura Selvi, D., & Saraswathy, S. (2017). Seed viability, seed deterioration and seed quality improvements in stored onion seeds: a review. The Journal of Horticultural Science and Biotechnology, 93(1), 1–7. https://doi.org/10.1080/14620316.2017.1343103