Skip to main content
ARS Home » Research » Publications at this Location » Publication #251009
Title: Water-triacylglycerol interactions affect oil body structure and seed viability

Author
item Walters, Christina
item Crane, Jennifer
item Volk, Gayle
item Ballesteros, Daniel
item Hill, Lisa
item Miller, Annette
item EIRA, MIRIAN - Embrapa
item Gardner, Candice
item Zee, Francis
item COONROD, DAREN - Cargill Citro-America
item WIESNEBERGER, LAUREN - O'Ahu Army Natural Resources Program
item YOSHINAGA, ALVIN - University Of Hawaii

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 5/23/2010
Publication Date: 5/23/2010
Citation: Walters, C.T., Crane, J., Volk, G.M., Ballesteros, D., Hill, L.M., Miller, A.L., Wiesneberger, L., Yoshinaga, A., Eira, M., Gardner, C.A., Zee, F.T., Coonrod, D. 2010. Water-triacylglycerol interactions affect oil body structure and seed viability [abstract]. Frontiers in Water Biophysics. p. 138-139.

Interpretive Summary: We are investigating interactions between water and triacylglycerols (TAG) that appear to affect oil body stability and viability of seeds. Dried seeds are usually stored at freezer temperatures (-20oC) for long-term conservation of genetic resources. This globally accepted genebanking practice is based on the assumption that low moisture and temperature slows chemical reactions associated with aging according to kinetic models of amorphous solids [1,2], and that TAG transitions within seeds are completely reversible. Increasingly, we are discovering exceptions to these kinetic models in species of seeds that contain TAG which crystallize and melt at temperatures greater than -25oC. The most dramatic effect of water-TAG interactions is massive cellular disruption and consequent seed death that results when fluid water is added to crystallized TAG [3,4]. A more subtle effect is observed in seeds containing proportions of monounsaturated:saturated fatty acids resulting in TAG crystallization temperatures between -5 and -25oC. These seeds tend to deteriorate faster in the freezer compared to seeds stored at higher storage temperatures and we hypothesize that the temperature anomaly is associated with TAG mobility as oil bodies restructure during crystallization induced by freezer storage. Thermomechanical analysis (TMA) shows major contraction and expansion of TAG-filled seeds during TAG transitions and dimensional changes are directly correlated with water content [5]. Differential scanning calorimetry (DSC) measurements show that increasing water content tends to increase the rate of TAG crystallization [3]. Electron micrographs show that temperature cycling through TAG transitions can lead to restructuring of oil bodies and incorporation of cytoplasmic materials [4,6]. Collectively, these observations suggest that oil and water may not mix, but they do interact. The interaction contributes to the instability of seeds during long term storage at freezer conditions. Seeds containing so-called tropical oils are prone to these temperature anamolies. Cooling at appropriate rates to liquid nitrogen temperatures can avoid TAG crystallization and prolong seed shelf life.

Technical Abstract: We are investigating interactions between water and triacylglycerols (TAG) that appear to affect oil body stability and viability of seeds. Dried seeds are usually stored at freezer temperatures (-20oC) for long-term conservation of genetic resources. This globally accepted genebanking practice is based on the assumption that low moisture and temperature slows chemical reactions associated with aging according to kinetic models of amorphous solids [1,2], and that TAG transitions within seeds are completely reversible. Increasingly, we are discovering exceptions to these kinetic models in species of seeds that contain TAG which crystallize and melt at temperatures greater than -25oC. The most dramatic effect of water-TAG interactions is massive cellular disruption and consequent seed death that results when fluid water is added to crystallized TAG [3,4]. A more subtle effect is observed in seeds containing proportions of monounsaturated:saturated fatty acids resulting in TAG crystallization temperatures between -5 and -25oC. These seeds tend to deteriorate faster in the freezer compared to seeds stored at higher storage temperatures and we hypothesize that the temperature anomaly is associated with TAG mobility as oil bodies restructure during crystallization induced by freezer storage. Thermomechanical analysis (TMA) shows major contraction and expansion of TAG-filled seeds during TAG transitions and dimensional changes are directly correlated with water content [5]. Differential scanning calorimetry (DSC) measurements show that increasing water content tends to increase the rate of TAG crystallization [3]. Electron micrographs show that temperature cycling through TAG transitions can lead to restructuring of oil bodies and incorporation of cytoplasmic materials [4,6]. Collectively, these observations suggest that oil and water may not mix, but they do interact. The interaction contributes to the instability of seeds during long term storage at freezer conditions. Seeds containing so-called tropical oils are prone to these temperature anamolies. Cooling at appropriate rates to liquid nitrogen temperatures can avoid TAG crystallization and prolong seed shelf life.