Longevity of seeds

When knowledge of the longevity potential of a seed

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: the flexibility of experimental design to accommodate the changing interests of future scientific communities that inherit the experiment. When knowledge of the longevity potential of a seed is finally understood, the next obvious experiments become assessments of putative protectants or ageing catalysts; however, by this time the seed is so irrevocably changed as to preclude analysis. The alternative approach of simulating ageing under adverse conditions (e.g. warm or moist), and extrapolating kinetics to more acceptable conditions (e.g. cold and dry), carries the implicit assumption that the mechanisms of deterioration are similar across a broad range of temperatures and relative humidities. This assumption is not universally supported in the literature (e.g. Walters, 1998) and is difficult to verify because of the dearth of longterm data. Given that there are different mechanisms resulting in seed death, it is also likely that different strategies that protect against deterioration have evolved in seeds. For example, persistence in soil seed banks may relate to the efficacy of dormancy mechanisms for the particular locale (Baskin and Baskin, 1998), the ability for intracellular repair (Villiers, 1974) or anti-microbial agents sequestered in seeds (Hendry et al., 1994). Although a link between seed dormancy or chemical defences and longevity in the genebank has been suggested, the relationship has not been tested formally. Because the mechanisms of deterioration and protection are likely to vary with the environment, one may hypothesize that seeds of different species have characteristic longevities, but relative longevity may vary with the storage condition. A better understanding of the seed ageing process will lead to more reliable predictions of seed performance under genebank conditions. Although the logistical problems of predicting how long seeds survive will probably not be solved for years to come, the research presented here provides an extensive dataset to document the kinetics of seed deterioration under cold (5 and 2 18 8C), dry (seed water contents maintained between 4 and 8%, depending on species) storage conditions, and to compare those kinetics across diverse species. This dataset, which constitutes monitoring results from the USDA-ARS National Center for Genetic Resources Preservation (formerly National Seed Storage Laboratory) seed collection, continues to grow as storage time increases and additional species are considered. It is believed that such data can provide an important tool for addressing hypotheses about seed ageing, and will ultimately lead to a better understanding of mechanisms of damage and the means to improve predictions of performance under a variety of conditions. The sigmoidal pattern of seed deterioration makes it difficult to summarize ageing kinetics. Previously developed viability equations (e.g. Ellis, 1991) accommodate this sigmoidal pattern using probits. However, since we wish to test hypotheses implicit to t...
View Full Document

Ask a homework question - tutors are online