Pj. Drew et al., 'Sub-imbibed' storage is not an option for extending longevity of recalcitrant seeds of the tropical species, Trichilia dregeana Sond., SEED SCI R, 10(3), 2000, pp. 355-363
Recalcitrant seeds of Trichilia dregeana were stored at 16 or 25 degreesC,
either at the water content at which they were shed or partially dried. Alt
hough having been exposed to a short period (approx. 6 h) at temperatures u
p to 30 degreesC prior to storage, seeds at the original water content main
tained viability for several weeks at 16 degreesC. However, storage of undr
ied seeds at 25 degreesC was deleterious within 8 d, indicating a chemical
basis for degeneration of hydrated recalcitrant seeds. Seeds that had been
mildly dehydrated to the relatively high axis level of 1.68 g H2O g(-1) dry
mass, while maintaining full germinability immediately after drying, exhib
ited only 4% viability after 8 d in storage at 16 degreesC and had complete
ly lost viability after the same storage period at 25 degreesC. Ultrastruct
ural features characterizing hydrated seeds included indications of enhance
d activity associated with initial exposure to the elevated temperature as
well as some signs of stress. However, over an effective 15 d storage perio
d at 16 degreesC, ultrastructural features showed the cells to have retaine
d little damage and to have been in an enhanced state of activity commensur
ate with ongoing development towards germination. After a longer storage pe
riod, however, signs of damage, including indirect evidence for disarray of
the cytoskeleton in some axis cells, became apparent in line with the decl
ining seed viability. Immediately following dehydration from an average axi
s water content of 1.97 to 1.68 H2O g g(-1) (the sub-imbibed condition), so
me ultrastructural abnormalities were apparent, but the seeds remained 100%
germinable. However, within the 8 d storage period in this sub-imbibed con
dition, a spectrum of severe ultrastructural degeneration, including indire
ct evidence of the collapse of the nucleoskeleton and extensive cell lysis,
accompanied viability decline of the seeds to 4%.