Effects of matriconditioning on onion seed germination, seedling emergence and associated physical and metabolic events

The effect of matriconditioning, the physiological presowing seed technique, using Micro-Cel E on Allium cepa L. cv. Czerniakowska seed quality was studied. Several ratios of seeds, carrier, water and time of priming were tested. The most effective treatment for improving onion seed germination at most tested temperatures was priming to a ratio of 2 g seed : 1 g Micro-Cel : 3 g water for 5 days in light at 15 degreesC. Matriconditioning greatly improved the germination and emergence percentage, seedling fresh and dry weight and reduced electrolyte leakage compared to that of untreated seeds; this beneficial effect was especially evident at suboptimal temperatures. Matriconditioning improved the germinability of aged seeds, the effect being more pronounced in the more aged seeds. No significant differences in ethylene production by primed and non-primed seeds were observed in the absence of its precursor, 1-aminocyclopropane-1-carboxylic acid (ACC), but its presence during imbibition caused an increase in ethylene production; an enhanced activity of in vivo ACC oxidase in Allium cepa matriconditioned seeds in comparison to untreated seeds, indicates that the endogenous level of ACC is a limiting factor of ethylene production. Likewise, the activity of ACC oxidase isolated from matriconditioned seeds was higher than that from untreated seeds. Higher endo-beta-mannanase and total dehydrogenase activities were observed in primed air-dried seeds in comparing to non-primed seeds.