Oxygen interacts with priming, moisture content and temperature to affect the longevity of lettuce and onion seeds

Lettuce (Lactuca sativa L.) and onion (Allium cepa L.) seeds have relatively short longevity during storage and their germination is sensitive to environmental stress. Seed priming (controlled hydration followed by drying) can improve seed germination under stressful conditions, inducing faster and more uniform germination over broader temperature ranges, but it can also reduce seed longevity in storage. Controlled deterioration (CD) tests are often employed to study longevity by ageing seeds rapidly at elevated temperature and moisture content, and primed seeds are particularly sensitive to CD conditions. As reactive oxygen (O-2) species are thought to be involved in seed deterioration, we tested whether storage under reduced O-2 atmospheres (0 and 2% O-2) would extend the longevity of primed and non-primed seeds under low relative humidity (RH) (33% RH + 37 degrees C) and CD (75% RH + 50 degrees C) storage conditions. The longevity of both non-primed and primed lettuce seeds in low RH storage was extended by anaerobic environments, but the effect of O-2 was much less under CD conditions. In onion, only primed seeds exhibited a beneficial effect of low O-2 atmospheres under both types of ageing conditions. In both species, storage under anaerobic conditions was beneficial for extending the longevity of primed seeds, but was not able to ameliorate fully the negative effect of priming on storage life.