Seed Storage and Seed Longevity

Summary

This presentation explores the complexities of seed longevity, focusing on the challenges of storing seeds from exceptional species that don’t adhere to standardized models. It highlights the importance of moisture and temperature in seed preservation, introduces the concept of 'intermediate' seeds, and investigates the impact of storage conditions on seed viability. The speaker also discusses papaya seeds as a case study, exploring their drying and temperature sensitivity. The presentation emphasizes the need for tailored storage solutions, using material science principles to predict and maximize seed longevity for a diverse range of species.

Takeaways

• 😀 Seed longevity is influenced by two main factors: moisture and temperature, and international standards guide genebanks in managing these conditions.
• 😀 Standardized seed storage methods may not be suitable for exceptional or unusual species, which require more nuanced approaches.
• 😀 Moisture and temperature affect seed longevity, with a 1% reduction in water content or a 10°F drop in temperature doubling the lifespan of seeds.
• 😀 Orthodox seeds follow established models of longevity based on moisture and temperature, but recalcitrant seeds do not.
• 😀 Seeds cannot be dried indefinitely—there is a critical moisture level below which longevity models fail, and overdrying can harm seeds.
• 😀 Temperature effects on seed longevity are complex, and extreme low temperatures like cryo-storage may not always provide the expected benefits for all seed types.
• 😀 Some seeds, like papaya, exhibit 'intermediate' characteristics, where they tolerate drying but may suffer from storage at extremely low temperatures.
• 😀 The concept of desiccation tolerance in seeds is difficult to measure quantitatively, especially for seeds with intermediate characteristics.
• 😀 Freezer storage doesn’t necessarily extend seed life as expected—some seeds age faster when stored in very low temperatures.
• 😀 Research on papaya seeds reveals the importance of managing both moisture and temperature carefully to maintain seed viability over long periods, with significant differences observed at various temperatures.
• 😀 Vitrification, the transition of seeds into a solid-like state during drying and cooling, is key to understanding seed longevity, with storage conditions influencing this process.

Q & A

What are the two main factors that affect seed longevity?

The two main factors affecting seed longevity are moisture content and temperature.

Why do standardized seed storage methods not always work for exceptional species?

Standardized methods often don't apply to exceptional species because these species may not conform to the general patterns that typical models use, particularly in terms of moisture and temperature tolerance.

What does Harrington’s Thumb Rule suggest regarding moisture and temperature control?

Harrington's Thumb Rule suggests that seed longevity can be doubled for every 1% reduction in seed moisture content or a 10°F reduction in temperature.

What is the relationship between seed moisture and longevity as per the Viability Equations?

The Viability Equations show an exponential relationship between seed longevity and moisture content, where lower moisture levels generally lead to longer seed lifespan, though this is not true for all species.

What is the main difference between orthodox and recalcitrant seeds?

Orthodox seeds follow standard models of longevity based on moisture and temperature control, whereas recalcitrant seeds do not survive these models and typically have very short lifespans under normal conditions.

What is meant by 'intermediate' seeds, and why are they significant?

'Intermediate' seeds refer to those that don't fully conform to either the orthodox or recalcitrant categories. These seeds may tolerate some drying but are damaged by extreme conditions, such as freezing, making them a challenge for storage.

What temperature anomalies were observed in seed storage, particularly with papaya seeds?

Papaya seeds showed unexpected behavior when stored at freezing temperatures. Storage at -5°C resulted in rapid deterioration, while storage at -18°C was somewhat better, and liquid nitrogen storage showed less deterioration over 15 years.

Why might papaya seeds deteriorate more quickly at low temperatures like -5°C?

Papaya seeds contain lipids that may crystallize and cause damage when exposed to temperatures around -5°C. This crystallization could accelerate seed deterioration, making these storage conditions unsuitable for papaya seeds.

How does the crystallization of lipids relate to seed longevity?

Lipids are large molecules that crystallize slowly. When stored at freezing temperatures, their crystallization can cause structural damage to the seed, impacting its longevity.

What concept from material science is being applied to seed storage in this research?

The concept of treating seeds as solid systems, similar to materials in engineering, is being applied. This approach helps better understand and predict seed stability and longevity by considering the structural and kinetic changes occurring during storage.