Enhanced aldolase activity and glycolysis as short term effects of hydrogen cyanide for the release of dormancy in walnut kernels

Seed dormancy removal by cold stratification is accompanied by the development of gluconeogenic competence. Although hydrogen cyanide can stimulate the germination of many herbaceous dormant seeds and increase gluconeogenesis in long term, its short-term effects on sugar metabolism require further investigation. Accordingly, an experiment in the form of complete randomized design was carried out to compare the effects of cold stratification and hydrogen cyanide on walnut (Juglans regia L.) kernel dormancy release and sugar metabolism. Imbibed walnut kernels were either cold stratified or pre-treated with hydrogen cyanide and changes in lipids, total soluble sugars, non-reducing sugars, starch as well as the activity of aldolase were assessed at two and 10 days after imbibition and compared to those of warm (27 °C) incubated kernels at the corresponding days. Walnut kernels pre-treated with hydrogen cyanide showed germination of about 88%, whereas the figure for warm incubated kernels was 52%. The cyanide-treated seeds before 10 days had lower levels of soluble sugars and starch but on the 10th day, had the greatest starch and highest aldolase activity compared to the cold-stratified and warm-incubated kernels. Lipid mobilization occurred in both warm incubated and cyanide pre-treated seeds but it was undetectable in cold stratified kernels. It was assumed that cyanide stimulates sugar glycolysis in the short term as evidenced by greater aldolase activity and decreased carbohydrate levels and in the next step through the activation of lipid gluconeogenesis leads to starch biosynthesis and the greater germination potential of walnut kernels.