Volatile Emission from Lettuce Seeds Stored for 25 Years.

Losses of seed viability during storage are currently measured, retrospectively, using germination assays. We are using headspace analysis of volatile organic compounds (VOC) to predict when seeds will lose viability as well as to non-invasively monitor changes in seed quality.   The presented experiments test whether the signature of VOCs change as a function of seed age and relative humidity after storage.  ‘Black-Seeded Simpson’ lettuce seeds were purchased every other year since 1991 and stored at 50% RH and 5C. Small samples of the seeds from each harvest were sealed into gas chromatography (GC) vials. Headspace in vials was sampled at 3 weeks, 3 months and 6 months and characterized using GC and an Agilent DB624 capillary column. Compounds were identified by retention time and verified by GC-mass spectrometry.  While a few major compounds were always detected in the headspace (e.g., pentane and methanol), there were also many molecular compounds present at barely detectable levels.  We found that the compounds and concentration varied with seed age.   The work contributes to a model of seed aging that arises from non-specific molecular degradation.  In this model, the kinetics of deterioration is dependent on the molecular mobility within dried seed matrices.