INSTYTUT DENDROLOGII

Abstract: Effects of several stratification variants on seed dormancy breaking were compared in Crataegus submollis Sarg. (hairy cockspur-thorn or Quebec hawthorn). Ripe seeds were collected (in October), cleaned, and dried to a moisture content of 7–12%. Seed dormancy in this species was broken most effectively by warm-cold stratification of nutlets, in a substrate or without any substrate, at 15~25°/3°C or 20~30°/3°C, i.e. with a cyclically alternating warm stage (16+8 hrs or 24+24 hrs/cycle) lasting 16–20 weeks, followed the cold stage lasting ca. 20 weeks, i.e. till the appearance of the first germinating seeds. After stratification, emergence rate is equally high (ca 50%) at cyclically alternating temperatures of 3~15°C and 3~20°C (16+8 hrs). Chemical scarification of nutlets in 96% sulphuric acid for 3 hrs, followed by warm-cold stratification at 20~30°/3°C, with a short, 4-week warm stage, also ensures a high emergence rate (58%). Seed desiccation (in nutlets) slowly to a moisture content of 10–12%, after stratification in a substrate or without any substrate as well as after scarification, results in a reduced emergence rate, especially if seeds are dried to the lower moisture content. Seed storage (in nutlets after drying to a moisture content of 10%) for 10 years at –3°C, does not decrease the emergence rate (93%) after stratification at 20~30°/3°C in a substrate, with a cyclically alternating warm stage (24+24 h) lasting 16 weeks.

Additional key words: stratification, scarification, germination, seedling emergence, desiccation, storage