Galactosyl-sucrose oligosaccharides and potential longevity of primed seeds

Correlative evidence indicates that sucrose and alpha -galactosyl-sucrose o ligosaccharides (raffinose family oligosaccharides; RFOs) may be involved i n seed longevity. Priming treatments (hydration in water or osmotic solutio ns followed by drying) can improve shortterm seed performance but often res ult in reduced seed longevity. As RFOs are metabolized quickly following se ed imbibition, loss of RFOs during priming could lead to more rapid deterio ration in dry storage. This hypothesis was tested by measuring sucrose and oligosaccharide contents and potential longevity of primed seeds. Raffinose contents of whole lettuce (Lactuca sativa L.) seeds declined during hydrat ion and priming and were correlated with decreased median potential viabili ty (ps,). However, this relationship was less significant when only the emb ryonic axes were analysed. In tomato (Lycopersicon esculentum Mill.) and im patiens (Impatiens balsamina L.) seeds, planteose was the major galactosyl- sucrose oligosaccharide and only small quantities of RFOs were present. Pla nteose contents declined during priming in seeds of both species, while suc rose contents increased or remained constant. Post-priming treatments that restored longevity in primed impatiens and tomato seeds were not accompanie d by consistent changes in RFO or planteose contents. Our data do not rule out a role for oligosaccharides in seed longevity, but they make it unlikel y that changes in oligosaccharide contents alone are responsible for the re duction in longevity due to priming or its restoration by post-priming trea tments.