Seed cooling: improving the longevity of ex situ conservation.

Ex situ conservation plays a critical role in preserving plant diversity through the use of botanical gardens, field gene banks, and seed banks. Seed banks, in particular, have proven their value as a tool for providing genetic resources for plant breeding and broader conservation efforts. With some 1,750 seed banks worldwide housing around 6 million samples, these collections protect the genetic material of thousands of plant species. However, the longevity of stored seeds is a critical factor in determining their usefulness over time. To extend the life of seeds and ensure their germination for future use, seed cooling techniques from Clitec have become an essential part of ex situ preservation.

Why seeds as the preferred hereditary material for storage

Seeds have unique adaptations that allow them to survive adverse conditions and enter a dormant state when conditions are unfavorable. The ability to tolerate drought and maintain cell structures by accumulating nutrient reserves makes seeds particularly well suited for long-term storage. By drying the seeds and reducing their metabolic activity, they can be preserved in a dormant state. This dormancy allows Clitec seed cooling cells to store a wide variety of plant species using standardized procedures and minimal space requirements, offering seeds an extended shelf life.

The role of temperature and relative humidity

The lifespan of seeds in storage depends on environmental factors such as temperature and relative humidity (RH). Orthodox seeds, the most suitable for seed storage, can be stored at temperatures between 60 °C and -20 °C and RH between 80 % and 30 %. Lower temperatures and reduced RH contribute to longer seed viability, with each 6 °C-10 °C drop in temperature approximately doubling viability. Freezer storage at -18 °C to -20 °C has become the international standard for conventional seed storage, as properly dried orthodox seeds can remain germinable there for 100-200 years. Clitec offers various products and sizes for this area. This extended survival makes ex situ preservation strategies more feasible and cost-effective.

Clitec seed storage and cooling challenges

Although seeds are generally well suited for long-term storage, some species show limited longevity, which presents challenges for seed banks. Certain seeds, including willows, elms, orchids, and species native to Hawaii, have intrinsically short life spans. Storage at low temperatures (-10 °C to -20 °C) can cause immediate damage or accelerated aging for certain genetic material, such as seeds high in certain storage lipids. Understanding the composition and organization of cellular components within seeds, as well as postharvest handling and storage environments, is critical to ensure their longevity.

Exploring glassy matrices and cytoplasmic stability with Clitec.

The stability and longevity of seeds can be compared to highly controlled synthetic systems such as food, pharmaceuticals and materials. The immobilization of molecules within glassy matrices characterized by crowding and irregular spacing affects the degradation rate. Seed longevity is likely influenced by similar principles, and factors such as cytoplasmic matrix organization and lipid crystallization play a role in determining a seed’s ability to survive freezing temperatures. By studying the thermal properties and behavior of storage lipids, scientists aim to improve the longevity of seeds during freezer storage. With our innovative Clitec technology and unique modulated refrigeration technology, our freezers offer unprecedented temperature stability and uniformity in daily operation.


Seed cooling techniques have revolutionized ex situ conservation efforts by enabling long-term storage and preservation of plant genetic resources. By taking advantage of the natural desiccation tolerance and dormant state of seeds, seed banks can protect a diverse genetic reserve for decades or even centuries. However, challenges exist in maintaining the longevity of certain seeds, necessitating further research to clarify the factors that influence their stability. Advances in seed cooling technologies and storage protocols, such as those offered by Clitec with products, will contribute to the success of ex situ conservation and ensure the availability of genetic resources for future generations.


Walters, C. and Pence, V.C. (2020) ‘The unique role of seed banks and cryobiotechnologies in plant conservation’, PLANTS, PEOPLE, PLANET, 3(1), pp. 83-91. doi:10.1002/ppp3.10121.