From the Seed Bank to the Field: What Storage Does to the Seeds of an Alpine Grass?

Many people may think that studying seed germination is quite a straightforward process, where scientists put their seeds under various different conditions until they eventually discover the ones where seeds germinate the most and more rapidly. Moreover, people expect that the germination results found in the lab will somehow reflect how well seeds will perform in the field. Unfortunately, especially for seed scientists like me, these things rarely occur or are as simple as that, mostly because seed germination is controlled by a myriad of factors both before, during, and after seed development. Among all these factors, perhaps one of the most striking for researchers are all the conditions that the seed faces once it has reached maturity, mainly because nowadays we subject seeds to conditions that they would never face in the wild: the conditions of a seed bank.

            Seed banks are facilities dedicated to the storage of seeds with the aim of conserving them under controlled conditions. Such conditions include low temperatures and low humidity, which aim to extend their shelf life for several decades. Seed banks dedicated to conserving our planet’s plant biodiversity have been growing and increasing so that these seeds can be used in the future, for example, to reintroduce species that have become extinct in the wild or to restore sites that have been degraded in some way. Given the practical importance of seed banks and the potential effect of storage conditions, it is increasingly necessary to undertake studies to understand how seed banking affects germination.

In a fascinating study recently published in Seed Science Research, researchers from the State Key Laboratory of Herbage Improvement and Grassland Agro-ecosystems of Lanzhou University evaluated how storage affected the germination of Elymus nutans –a perennial grass from the alpine meadows of the eastern Qinghai-Tibet Plateau. Specifically, they aimed to evaluate whether storage affected germination responses to temperature and seedling emergence in the field and if these were somehow related.

The researchers collected seeds in ten populations along an elevation gradient across the eastern Qinghai-Tibet Plateau in sites ranging from 2800 to 3600 m above sea level. These seeds were germinated under different temperature conditions in the laboratory, either immediately after collection or after six months in storage at room temperature. A similar experiment was conducted by planting the fresh and stored seeds of the ten populations in three different sites across the same elevation gradient. Altogether, these two experiments allowed the researchers to evaluate whether storage alters the temperature conditions required for germination and if this translates to changes in seedling establishment in the field.

Interestingly, seeds stored for six months germinated more quickly than fresh seeds, regardless of the population they originally came from. Stored seeds also required higher temperatures to germinate but require less exposure time to achieve it. More notably, the variation in germination responses was reduced in stored seeds, suggesting that storage made the responses of the different populations of this species more homogeneous. Therefore, these results imply that storage altered the physiology of Elymus nutans seeds by increasing their germination capacity and shifting their temperature requirements.

Such a positive effect was also observed in the field experiment, where the crested seeds had a higher establishment success and even higher survival rates in some populations. Storage did not have the same homogenising effect observed in the laboratory experiments, suggesting these physiological effects are not translated to the field. 

Still, one thing is clear: seed storage seems to be a very promising tool for ecological restoration. Instead of using the seeds immediately after they are collected, they can be stored for more effective sowing. Storage has already been reported as a useful technique for breaking shallow non-deep physiological dormancy –the same dormancy class present in Elymus nutans– but this study is the first of its kind to demonstrate its practical applicability with a large number of populations and over a considerable environmental gradient. Previous studies have shown that storage can positively or negatively affect seedling establishment in the fill. Still, these promising results underscore the importance of assessing such effects, as they might hold the key to more successful restoration projects.

READ THE PAPER:

Chen, D., Yuan, H., Bao, J., Zhao, X., Fu, X., & Hu, X. (2024). Dry storage alters intraspecific variation in phenotypic traits at early life stages: evidence from a dominant alpine meadow species. Seed Science Research, https://doi.org/10.1017/S0960258523000223

Carlos A. Ordóñez-Parra

Carlos (he/him) is a Colombian seed ecologist currently doing his PhD at Universidade Federal de Minas Gerais (Belo Horizonte, Brazil) and working as a Science Editor at Botany One and a Social Media Editor at Seed Science Research. You can follow him on X and BlueSky at @caordonezparra.

Spanish and Portuguese Translation by Carlos A. Ordóñez-Parra. (in progress)