Submitted to: Seeds International Workshop Proceedings
Publication Type: Abstract only
Publication Acceptance Date: 5/11/2002
Publication Date: 5/11/2002
Citation: Bailly, C., B. Poli, F. Corbineau, and C. Walters. 2002. Storability of primed sunflower seeds as related to water status. 7th International Workshop on Seed Biology, May 11-19, 2002, Salamanca, Spain. Interpretive Summary: This work studies changes in the water status of sunflower seeds during aging and priming in an attempt to understand the why primed seeds tend to age faster when redried. The subtle changes in water sturcture in primed and aged seeds suggests a decreasing viscosity in the aqueous matrix which might make cellular constiuents more prone to aging reactions.
Technical Abstract: Osmopriming of sunflower seeds with a polyethylene glycol-8000 solution (-2 MPa) at 15 degrees Celsius for 7 days increased their subsequent germination rate at 15 degrees Celsius and their deterioration during accelerated ageing (45 degrees Celsius, 100 % RH). In order to determine whether the rapid germination and poor storability of primed seeds was related to changes in water status, water sorption isotherms and differential scanning calorimetry (DSC) analysis were used to measure thermodynamic properties of water in seeds. Isotherms were fit to a D'Arcy/Watt model or subjected to Van't Hoff analyses to determine enthalpy of water associations on seed constituents at different water contents. Though, major differences in seed water status were not observed after priming, primed seeds tended to have slightly higher water contents at a given relative humidity, but lower binding enthalpies, than their unprimed counterparts. DSC analyses showed evidence of glass-type transitions in primed and unprimed sunflower seeds, with transition temperatures (Tg) being slightly lower for dry primed seeds. State/phase diagrams and isopleths were constructed from water content, relative humidity, and water property data to gain insights about the physiological processes associated with priming and with the poor storability of primed seeds. We speculate that priming results in weakened water-substrate associations, which lead to a decrease in the viscosity of the aqueous matrix. The greater fluidity could lead to accelerated germination at high water potentials and precocious ageing at intermediate water potentials.