Submitted to: Planta
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/21/2005
Publication Date: 9/1/2005
Citation: Walters, C., P. Landre, L.M. Hill, F. Corbineau and C. Bailly. 2005. Organization of lipid reserves in cotyledons of primed and aged sunflower seeds. Planta 222:397-407. Interpretive Summary: This research explores changes in storage lipids as sunflower seeds are primed and aged. Usually changes in storage reserves are overlooked during early stages of seed germination or aging. We show significant changes in their organization within the cell that can be detected non-invasively by studying changes in the crystallization behavior. Crystallization behavior of lipids in seeds may be responsible for several aspects of seed storage behavior.
Technical Abstract: Storage of sunflower (Helianthus annuus L.) seeds at intermediate water potentials leads to faster germination (priming) or slower germination (accelerated aging) depending on the temperature and duration of storage. Such changes in seed vigor are likely to be associated with changes in the major food reserve in sunflower lipids. Morphological, biochemical and phase properties of lipid reserves were compared in freshly harvested (i.e., control), primed and aged sunflower (cv Briosol) cotyledons using electron microscopy, biochemical analyses and differential scanning calorimetry, respectively. Lipid bodies became smaller and more dispersed throughout the cytoplasm during priming and aging. Despite ultrastructural changes, lipid content within the cotyledons remained close to 50% of the dry matter of the seed and the level of saturated and unsaturated fatty acids was unchanged in primed and aged seeds, with only severely aged seeds showing a net decrease in linoleic acid. Typical of triacylglycerides, the lipids in sunflower seeds exhibited polymorphic crystalline and amorphous solid phases when cooled to subzero temperatures. Priming decreased the crystallization efficiency (rate of crystallization) of lipids in vivo and aging increased the crystallization efficiency but decreased total crystal formation. These changes in the thermal behavior of lipids in vivo are consistent with losses and gains, respectively, of interacting non-lipid moieties in the triacylglyceride matrix, which may be relevant to the disassembly of liposomes during germination or high-humidity aging.