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Unformatted text preview: 46, despite a higher
storage temperature, smaller number of species and
smaller range of P50s. Maximum germination in the
Duvel buried seed experiment occurred in years 1 to 39,
with a median of 6 years (Toole and Brown, 1946).
Although the surveys of Duvel and Priestley et al.
(1985) reported similar average life spans, species that
persisted in the soil were not the same ones that
survived in storage bins (Table 3). These results
demonstrate that expected longevities among widely
varying experiments are comparable when seeds are
stored under controlled, relatively dry, conditions.
However, there was no signiﬁcant trend observed
between seed persistence in a temperate-mesic soil seed
bank (Table 4, last column) and seed longevity under
controlled storage conditions, suggesting, perhaps,
that the mechanisms of deterioration and protection
are different in these contrasting environments.
Signiﬁcant correlation of P50 values (P , 0.03 or
P , 0.10) among different surveys (Table 4) demonstrates that the relative tendency for species to age is Longevity of seedbank-stored seeds 11 Figure 2. Germination time courses for six species in the USDA National Plant Germplasm System (NPGS) collection
constructed from viability monitoring data. Storage time versus percent germination for individual accessions (open circles)
were averaged in 4-year increments (solid circles) and the ageing characteristic was calculated by ﬁtting the averaged time
course to the Avrami equation (see Methods section) (curve). The time courses and ﬁtted curves described in this ﬁgure are
typical of the interpolation (B. vulgaris, A. hypogaea and C. melo) or extrapolation (R. sativus, M. alba and P. sativum) required to
calculate the time for seed germination to decrease to 50%. Avrami parameters and calculated P50 values for each species are
listed in Table 1 (NPGS collection) and Table 2 (Stanwood, unpublished). consistent among experiments, and supports the
hypothesis that species have characteristic ageing
behaviours. For the surveys considered in this paper,
species were divided into three categories, based on
whether the P50 was in the lowest, middle or highest
third in the experiment (analysis not shown). Species
that were placed in the same category in two or more
experiments were considered to have short, medium or long life spans respectively, relative to other species
(Table 3, right-hand column). For example, Allium cepa
(Liliaceae), Bromus inermis (Poaceae) and Festuca rubra
(Poaceae) had consistently low P50s and were placed in
the short shelf-life category, while Abelmoschus esculentus (Malvaceae), Lycopersicon esculentum (Solanaceae),
Pisum sativum (Fabaceae) and Raphanus sativus (Brassicaceae) had consistently high P50s and were placed in C. Walters et al. 12 Table 2. Storage performance of seeds in an experiment initiated by Stanwood in 1977 to compare longevities of species at
different storage temperatures (results of liquid nitrogen study published in Walters e...
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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.
- Spring '13