Submitted to: Journal of Experimental Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 5, 2010
Publication Date: September 5, 2010
Citation: Mira, S., Gonzalez-Benito, E., Hill, L.M., Walters, C.T. 2010. Characterization of volatile production during storage of lettuce (Lactuca sativa) seed. Journal of Experimental Botany. 61:3915-3924. Interpretive Summary: Problem: The early stages of seed deterioration are asymptomatic and then seeds suddenly and rapidly die. The objective of this work was to develop assays that detect and quantify change during the asymptomatic stage of seed deterioration and to relate the kinetics of this change to the duration that seeds stay viable in storage. Accomplishment: We quantitatively sampled the airspace above stored lettuce seeds, identified over 30 compounds by gas chromatography and gas chromatography-mass spectroscopy, and measured the kinetics of emission. Volatiles were categorized as originating from glycolytic, peroxidation or flavor related reactions, and proportions of the various reactions varied with the storage moisture content. Rate of production of glycolytic byproducts was strongly related to the duration of the asymptomatic phase of seed deterioration. Impact: We have developed an assay that non-invasively detects reactions in seeds before losses in viability are detected and correlates with the initial rate of seed aging. The assay involves sampling the airspace within a seed storage package and is completely non-invasive.
Technical Abstract: The duration that seeds stay vigorous during storage is difficult to predict but critical to seed industry and conservation communities. Production of volatile compounds from lettuce seeds during storage was investigated as a non-invasive and early detection method of seed aging rates. Over thirty volatile compounds were detected from lettuce seeds during storage at 35ºC at water contents ranging from 0.03 to 0.09 g H2O g-1 dw. Both qualitative and quantitative differences in volatile composition were noted as a function of water content, and these differences were apparent before signs of deterioration were apparent. Seeds stored at high water content (> 0.06 g H2O g-1 dw) emitted molecular species reminiscent of glycolysis (methanol + ethanol), and evidence of peroxidation was apparent subsequent to viability loss. Seeds containing less water (0.03-0.05 g H2O g-1 dw) produced volatiles reminiscent of peroxidation and survived longer compared to seeds stored under more humid conditions. Production of glycolysis-related byproducts correlated strongly with deterioration rate when measured as a function of water content. This correlation may provide a valuable means to non-invasively predict the duration of the early, asymptomatic stage of seed deterioration.