, Volume 77, Issue 1, pp 111-122

Rapid watet uptake and structural changes in imbibing seed tissues

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Studies on ultrastructure in tissues from air-dry seeds normally involve fixation in aqueous media. Recent freeze-etch studies suggest that water is taken up extremely rapidly by these tissues with attendant structural change. Measures have now been made of water uptake by small (<400μg) pieces ofHordeum vulgare scutellum,Pisum sativum cotyledon and radicle, andHelianthus annuus cotyledon. Measurable water uptake occurred within 10 seconds, and scutellum was already saturated (160% of initial air-dry weight) within 2 minutes. Tissues re-dried almost as rapidly. Barley scutellum was investigated by freezeetching. Air-dry tissue, frozen direct in liquid nitrogen or surrounded by 100% glycerol, had convoluted cell walls, organelles with indented margins, and polyhedral lipid bodies which were in such close mutual proximity as to nearly form closed lipid sheets over plasmalemma and protein bodies. Within 8 seconds of exposing to water, cell walls had straightened and organelles and lipid bodies rounded out. It is likely that many descriptions of structure in “air-dry” seeds have been of this hydrated structure.