This PPT focuses on the concept of seed ageing, describing it as a natural, inevitable process in which seeds gradually lose quality, vigour, and germination capacity during storage. Since seeds are living entities, they undergo a series of physiological, biochemical, and structural changes soon after physiological maturity and during the storage phase. These changes collectively lead to seed deterioration, reduced field performance, poor stand establishment, and ultimately loss of germinability.
The presentation explains that seed ageing is both an inexorable and irreversible process. Although deterioration cannot be reversed once it has occurred, the rate of ageing can be slowed. Seed ageing varies among species, varieties, seed lots, and even among individual seeds within a lot. The PPT emphasizes that stored seeds are critical assets for growers, as uniform and successful establishment is essential for strong crop growth.
The mechanisms of seed ageing are discussed in detail, highlighting oxidative damage to macromolecules such as lipids, proteins, enzymes, and nucleic acids. Free radicals, formed through ionizing radiation, enzymatic reactions, transition metals, and normal metabolic processes, play a central role in oxidative degradation. One of the earliest effects of ageing is the loss of cellular membrane integrity, resulting in increased leakage of metabolites due to phospholipid hydrolysis and lipid autoxidation. Mitochondrial degradation, including swelling, loss of function, pigmentation, and fragmentation, further contributes to reduced seed viability.
The PPT also explains the activation of hydrolytic enzymes when seed moisture approaches levels required for germination. If germination does not proceed normally, continued enzyme activity leads to energy depletion and accumulation of breakdown products, accelerating deterioration. Additionally, the breakdown of mechanisms responsible for triggering germination contributes to ageing-related loss of viability.
Another major aspect covered is genetic degradation, where progressive fragmentation and oxidative damage of embryonic nuclear DNA occur during seed ageing. DNA damage may result from uncontrolled oxidation or programmed cell death–like processes.
Visible symptoms of seed ageing include morphological changes such as darkening of the seed coat, development of necrotic lesions in cotyledons, increased membrane leakage, and loss of enzyme activity. Enzymes commonly associated with seed deterioration include dehydrogenase, catalase, peroxidase, amylase, and cytochrome oxidase.
The PPT concludes that seed ageing affects multiple cellular systems simultaneously and that deterioration is not limited to a single function. Environmental storage factors such as seed moisture content, oxygen availability, relative humidity, and temperature play a decisive role in determining seed longevity and storability. Understanding these factors is essential for improving seed storage practices and maintaining seed quality over time