What are the factors that affect the longevity of seeds during storage in warehouses? Describe.

Factors Affecting Seed Longevity During Storage

Seed longevity is not a static property; it is influenced by a complex interplay of genetic, physiological, and environmental factors. These factors can be broadly categorized into intrinsic (seed-related) and extrinsic (environmental) factors.

Intrinsic Factors (Seed-Related)

These factors are inherent to the seed itself and are largely genetically determined. However, pre-harvest practices can influence these factors to some extent.

• Genetic Constitution: Different varieties of the same crop species exhibit varying seed longevity. Some genotypes possess inherent mechanisms to resist deterioration better than others. For example, certain traditional rice varieties might demonstrate better storage potential compared to modern, high-yielding varieties.
• Seed Maturity: Immature seeds have higher metabolic activity and moisture content, leading to faster deterioration. Proper harvesting and maturation are crucial.
• Moisture Content: This is arguably the most critical intrinsic factor. Higher moisture content (typically above 12%) accelerates enzymatic reactions and microbial growth, leading to rapid deterioration. Seeds with lower moisture content (<12%) have significantly longer storage life.
• Lipid Content and Oxidation: Lipids are susceptible to oxidation, leading to rancidity and loss of viability. Seeds with higher lipid content are generally more prone to deterioration. Antioxidant levels within the seed also play a vital role.
• Protein Content: While not directly causing deterioration, high protein content can sometimes contribute to issues like crust formation and insect infestation during storage.
• Dormancy: A degree of dormancy can sometimes be beneficial, allowing for a period of quiescence before germination. However, excessive dormancy can mask deterioration.

Extrinsic Factors (Environmental)

These factors relate to the storage environment and are often manageable through appropriate warehouse practices.

• Temperature: Temperature is a major factor influencing seed longevity. Higher temperatures accelerate metabolic reactions and enzymatic activity, leading to faster deterioration. The Arrhenius equation describes the relationship between temperature and reaction rate. Generally, lower temperatures (around 5-10°C) are ideal for long-term seed storage.
• Relative Humidity (RH): High RH promotes moisture absorption by seeds, increasing their internal moisture content and accelerating deterioration. Ideal RH for seed storage is typically below 65%, and controlled humidity systems are often employed in modern seed warehouses.
• Oxygen Availability: Oxygen supports aerobic respiration, a major contributor to metabolic deterioration. Reducing oxygen levels (controlled atmosphere storage – CA) can significantly extend seed longevity.
• Light Exposure: Light can induce seed germination and accelerate deterioration in some species. Storage in dark conditions is generally recommended.
• Pest and Disease Infestation: Insects (e.g., weevils, moths) and fungal pathogens can damage seeds and accelerate deterioration. Proper fumigation and sanitation are essential.
• Seed Packaging: The type of packaging material used can impact seed longevity. Moisture-proof and airtight containers are crucial for preventing moisture absorption and pest infestation. Bags made of materials like polyethylene are commonly used.

Factor	Effect on Longevity	Mitigation Strategy
High Temperature	Accelerates deterioration	Maintain low storage temperature (5-10°C)
High RH	Increases moisture content	Use dehumidifiers, airtight containers
High Oxygen	Promotes respiration	Controlled atmosphere storage (CA)
Pest Infestation	Physical damage, fungal growth	Fumigation, sanitation

The Central Seed Certification Agency (CSCA) under the Department of Agriculture and Farmers Welfare, Government of India, plays a crucial role in regulating seed quality and storage practices, ensuring compliance with national and international standards.

Case Study: Controlled Atmosphere Storage in Australia

Australian seed banks, like the Millennium Seed Bank Partnership at Kew, extensively utilize controlled atmosphere (CA) storage. Seeds are stored in sealed containers with reduced oxygen levels (typically 1-3%) and controlled temperature (around -20°C). This drastically slows down metabolic processes, extending seed longevity by decades. This technique is particularly vital for preserving rare and endangered species.