Effects of low temperatures on changes in oligosaccharides, phenolics and peroxidase in inner bud of onion Allium cepa L. during break of dormancy

The effects of low temperatures on the break of dormancy of onion bulbs and changes in oligosaccharides, phenolics and peroxidase activity were examined. Cold treatment at 9 degrees C was more affective on break of dormancy than at 0 degrees C, but in both cases cold temperatures caused a rapid break of dormancy. Changes in oligosaccharides and glucose were linked to sprouting stages, with higher concentrations at the onset of sprouting for cold treatments of 9 degrees C for 3 weeks and 0 degrees C for 3 weeks, for the other treatments (9 degrees C for 2 weeks and 0 degrees C for 3 weeks) the high concentrations were reached after sprouting. There was an inverse relation between sprouting on the one hand, and phenolics and peroxidase activity on the other hand. These results emphasized a positive effect of low temperature on breaking dormancy of onion bulbs and the negative role of phenolics and peroxidase on inner bud development.