Theoretical Basis of Protocols for Seed Storage

Abstract

The protocols presently established for optimum seed storage do not account for the chemical composition of different seed species, the physiological status of the seed, and the physical status of water within the seed. The physiological status of seeds from five species with varying chemical compositions was determined by measurements of rates of oxygen uptake and seed deterioration. The physical status of water was determined by water sorption characteristics. For each species studied, there was a specific moisture content for the onset of respiration, chemical reactions, and accelerated aging rates. The moisture contents at which these physiological levels were observed varied among the species and correlated with the lipid content of the seed. However, the changes in physiological activifies and the physical status of water occurred at specific relative humidities: 91% for the onset of respiration, 27% for the increased rates of thermal-chemical reactions, and 19% for optimum longevity. Based on these observations, we propose that equilibrating seeds between 19 and 27% relative humidity provides the optimum moisture level for maintaining seed longevity during longterm storage.mendations of the IBPGR (3). Based on limited empirical information, calculations from the viability equations, and practical considerations, the IBPGR recommends that seeds be stored at moisture contents between 3 and 7%, depending on the seed (10). For seeds with poor storage characteristics, further drying may be recommended (3, 5, 7). Unfortunately, these recommendations do not aid the gene bank operator in determining the optimal moisture content for storage of a particular seed species, cultivar, or lot.A more theoretical approach to the study of the effect of water content on seed deterioration would alleviate some of the intrinsic difficulties of a strictly empirical approach. Protocols developed from physical principles will obviate the need to determine optimal conditions for each species, varying cultivars within a species, and specific tissues within an individual seed.Intuitively While scientists have known for many years that dry, cold conditions will increase shelf life of biological material, the optimum moisture level and temperature are poorly understood. Since studies of the optimal environment for storage are intrinsically difficult because they take years, scientists have relied on experiments of seed aging under less optimal conditions and then extrapolated beyond their data. Based on these empirical data, equations have been derived to predict the rate of seed deterioration under various conditions (6,21). The assumption of these equations has been that the effect of water content on the rate ofseed deterioration is a logarithmic relationship and thus, the drier the tissue is, the longer it will maintain viability (5-7).The viability equations are the basis of the storage recom-1019 where k2 is proportional to the rate of a reaction, Z is a coefficient related to the rate of molecular collisions, Ea is the...

Influence of vacuum packaging on seed quality and mineral contents in chilli (Capsicum annuum L.)

“…While, the freshly harvested seeds had the protein content of 75.2 mg/g. This indicates that the protein content in the seeds is also subjected for deterioration depending on the storage conditions indicating its sensitivity to moisture, light, temperature and oxygen (Vertucci and Roos 1990). Loss of protein content was maximum in jute bags stored at room temperature which could be mainly attributed to property of protein chains forming loose mesh when the moisture content is more.…”

Simplificação da equação de viabilidade para predizer a longevidade de sementes de milho e soja

“…Como a semente está exposta diretamente às mudanças climáticas no armazém, a umidade relativa pode estar mais diretamente relacionada à atividade química da água. Assim, seria mais relevante discutir as mudanças fisiológicas da semente em termos termodinâmicos do que com base na umidade da semente, como tem sido preconizado por Vertucci & Roos (1990. Isso foi comprovado por Ellis et al (1990) que, comparando a umidade da semente com a umidade relativa de equilíbrio de amendoim, beterraba, cebola, cevada, grão-de-bico, soja, trigo e vigna, concluíram que o efeito relativo do potencial hídrico foi o mesmo para estas espécies e, provavelmente, para outras espécies ortodoxas.…”

Water Sorption Isotherm Characteristics of Seeds of Six Indigenous Forest Tree Species in Ghana

“…Isotherms are also useful for analyzing seed water-binding properties (Merritt et al, 2003). The strength and nature of water binding in seeds is considered to influence the rate of deteriorative reactions (Vertucci & Roos, 1990). Therefore, waterbinding characteris-tics may be a factor in the variation in seed longevity between different species, although any relationships between seed water-binding properties and storage behavior are yet to be resolved (Eira et al, 1999).…”

“…Seed water content is crucial to long-term survival of stored seeds, as it affects the rate of metabolic and deteriorative reactions (Vertucci & Roos, 1990). There appears to be critical water content level above and below which seed ageing rates increase (Walters, 1998).…”