INSTYTUT DENDROLOGII

Study of breaking seed dormancy of some species from the genus Crataegus

Seeds of numerous trees and shrubs require specific environmental conditions to initiate germination. The cardinal ones include appropriate temperature, air access and humidity. As far as Crataegus is concerned, its deep dormant seeds, are often observed to remain dormant in the ground for 2 or even 3 years. A series of temperature stratifications and acid scarification treatments were evaluated for breaking seed dormancy in 4 Crataegus species: Crataegus monogyna, C. laevigata, C. pedicellata, C. submollis The most advantageous time for collecting fruits of the Crataegus species falls on October, when they are fully ripe. The stones extracted from the fruits must be dried at room temperature to the moisture content of about 10%. Seeds were, in three replications of 50 seeds each, subjected to the following treatments: cold stratification at 3°C in the stratification medium (sand and peat, volume ratio 1:1), warm-followed by-cold stratification first at 15°, 20°, 25°, 30°C, with the warm phase lasting of 8-24 weeks followed by the cold phase at 3°C until first seedlings appear, warm-followed by-cold stratification with the warm phase at cyclically alternating temperature 15°~20°C and 20°~30°C (16/8h , 24/24h) for 8-24 weeks. After stratification, the seeds were subject to germination tests in the same medium as was used for stratification at 3~10°C, 3~15°C, 3~20°C and 3~25°C (16+8 h) and emergency tests at 3~15°C, 3~20°C. Stones were subjected to scarification in the concentrated sulphuric acid for 1,2,3 hours. The seeds were dried to the moisture content of 10%. The dormancy of the Crataegus seeds can be overcome by their stratification in thermal regimes 20°~30°/ 3°C (16 weeks at 20°~30°C (16/8h or 24/24h) followed by 15-18 weeks at 3°C, i.e. to the time when first seedlings start to appear). Having been stratified, the seeds germinate vigorously (in 3-5 weeks) and at a high percentage at temperatures of 3~20°C (16+8 h) and the seedlings emerge at 3~20°C (16+8 h) in 3-6 weeks. Storage for one year at -3°C in the case of the seeds dried after harvest to the moisture content of 10% does not reduce their germination capacity. Stones scarification for 2 hours followed by short stratification at 20°~30°C (4 weeks) and stratification at 3°C has an not adverse affect on germination seeds at the temperature 3~20°C (16+8 h). It is recommended that stratified seeds should be sown into the still cool soil at the end of March or the beginning of April, as the increased temperature induces the secondary dormancy in seeds.