Longevity of seeds

The ageing rate characteristic of seeds of individual

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Unformatted text preview: diversity, seed Introduction Seed genebanks maintain genetic resources within seeds over decades or centuries. The ageing rate characteristic of seeds of individual species provides essential guidelines for storage conditions, monitoring and regeneration needs of the genebank. Seed longevity is usually reported as studies of survival (e.g. Odum, 1965; Roos and Davidson, 1992; Shen-Miller et al., 1995; Steiner and Ruckenbauer, 1995; Telewski and Zeevaart, 2002), which highlight the remarkable ability of the seeds of some species, or seed lots, to remain viable for many years. In contrast, anecdotal accounts of rapid deterioration have led to the classification of some species as ‘bad keepers’. Neither of these types of studies provides a quantitative assessment of the expected behaviour of a species in a genebank situation. Surveys that compare seed ageing rates among several species stored under similar conditions provide estimates of the inherent longevity of a species relative to others. This information is critical to the understanding of the evolution of seed longevity and will provide a biological basis to help genebank operators prioritize processing procedures. The notable experiments of Beal and Duvel measured germination of seeds in the soil after 120 and 39 years, respectively (Telewski and Zeevaart, 2002; Toole and Brown, 1946, respectively). The bulk of information on relative longevity for seeds in non-field conditions is provided by Priestley and Ellis and their colleagues. Priestley et al. (1985) surveyed monitoring records of 92 species in ‘open’ storage at 13 locations in temperate climates. Presumably, ‘open’ storage refers to a warehouse environment with little control of temperature or relative humidity (RH). Ellis and colleagues measured deterioration time-courses of species stored at relatively high temperatures or water 2 C. Walters et al. contents, and produced coefficients that could be used to predict deterioration rates under less extreme conditions (Dickie and Bowyer, 1985; Dickie et al., 1985, 1990; Ellis et al., 1986, 1988, 1989, 1990a, b, 1996; Tompsett, 1986; Kraak and Vos, 1987; Belletti et al., 1991; Zewdie and Ellis, 1991). Other survey studies (Went, 1969; Rincker, 1981, 1983; Roos and Davidson, 1992; Hendry et al., 1994) have contributed to the idea that potential life spans of seeds vary among species. Relative longevity data among the various experiments have not been compared, probably because each study focused on different species. Long-term studies, where seed viability is monitored periodically, provide direct evidence of changes in germination percentage with storage time (Went, 1969; Rincker, 1981, 1983; Priestley et al., 1985; Roos and Davidson, 1992; Specht et al., 1998). Despite the number of established genebanks, these types of data are rare, probably because the early stage of seed ageing is asymptomatic, and it takes years before the cataclysmic decline in germination ability occurs. The long time required to reliably quantify seed life spans presents curatorial problems relating to the stability of infrastructure and funding, the reliability of measurements as methods and personnel change, and...
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This note was uploaded on 03/03/2013 for the course SFSF 202 taught by Professor Sf during the Spring '13 term at Cambridge.

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