Submitted to: Planta
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 1, 2003
Publication Date: March 1, 2003
Citation: Crane, J., A.L. Miller, J.W. van Roekel and C. Walters. 2003. Triacylglycerols determine the unusual storage physiology of Cuphea seed. Planta 217:699-708. Interpretive Summary: Cuphea seeds are valued in the food and petro-chemical industry because of their unusual fatty acid composition (short and medium chain lengths). Valuable germplasm of this potential new crop could not be stored in genebanks because seeds of some species were killed by the storage conditions. Based on the lipid composition, we have determined which species are susceptible to damage, the mechanism of the damage and how it can be ameliorated. Protocols to safely preserve Cuphea seeds are presented. We believe that the work is applicable to many species endemic to tropical areas.
Technical Abstract: Many species within the genus Cuphea (Lythraceae) produce seed with high levels of medium-chain fatty acids. Seeds of some Cuphea species lose viability when placed into storage at -18C. These species tolerate significant drying to 0.05 g Water/g and may, therefore, be intermediate in their storage characteristics. The thermal properties of seed lipids were observed using differential scanning calorimetry. Species with peak lipid melting temperatures less than or equal to 27C were found to be sensitive to -18C exposure while those with melting temperatures < 27C were able to tolerate low temperature exposure. This relationship was determined by the triacylglyceride composition of the individual species. Sensitive species have high concentrations of lauric acid (C12) and/or myristic acid (C14). Species with high concentrations of capric or caprylic acid or with high concentrations of unsaturated fatty acids tolerate low temperature exposure. Potential damage caused by low temperature exposure can be avoided by exposing seeds to a brief heat pulse of 45C to melt solidified lipids prior to imbibition. The relationship between triacylglyceride behavior in vivo, seed storage behavior and sensitivity to imbibitional damage is previously unreported and may apply to other species with physiologies which make them difficult to store.