Sugar metabolism as related to the cyanide-mediated elimination of dormancy in apple embryos

Embryos isolated from dormant seeds of apple (Malus domestica Borb., cv. Antonowka) were treated by gaseous HCN (1 mM) for 6 h and then cultured in the light for 9 d in parallel to control non-treated embryos. Soluble sugars were quantified, and oligosaccharide hydrolysing enzyme activities were determined in axes and in cotyledons of such embryos during culture. HCN pre-treatment stimulated germination and hydrolysis of oligosaccharides in embryonic axes. Hydrolysis of sucrose in the lower cotyledon (in contact with wet medium and therefore growing and greening faster) was affected by HCN to a small extent. On the other hand, growth, greening and sucrose hydrolysis in the upper cotyledon were stimulated by HCN pre-treatment to the levels observed in lower cotyledon. It is postulated that endogenous HCN in apple seeds controls the removal of embryonic dormancy in parallel to the earlier described control by light and gibberellin. Gibberellin was demonstrated to act on the hydrolysis and further transformations of storage lipids, including gluconeogenesis, but not β-oxidation of fatty acids. It appears that hydrolysis of oligosaccharides and their catabolism is the target for cyanide.