Research On Dormancy Formation And Breaking Of Chinese Dwarf Cherry (C. Humilis Bge.) Seeds

The seed of Chinese dwarf cherry (Cerasus humilis(Bge)Sok) is small with thick shell and deep dormancy. So the seed is difficult to germinate and the germination rate is low, which reduce the efficiency of crossbreeding. By using Chinese dwarf cherry ’Nongda No.4’ as material in this study, the seeds dormancy mechanism was studied from two perspectives:dormancy formation and dormancy breaking, offering technical support to improve the germination and providing reference for the research on dormancy of seeds of fruit trees. The main results were as follows:1. Seeds of Chinese dwarf cherry could germinate in the early stage of its development by removing the seed shell and coat. The germination rate reached to88.33%and44.22%(77d and84d after blossom), but germination rate of the seeds with shell was0%. The rate of germination was gradually reducing in the later stage and the germination rate dropped to15%and0%(140d and145d after blossom). It was also found that the water and the air were hard to penetrate into seeds because of the seed shell, and there were inhibitory substances presented in different part of seeds. So the dormancy of the seed of Chinese dwarf cherry was comprehensive dormancy.2. Respiratory intensity, water content were decreasing during seed developing, while soluble sugars, starch, fat and protein contents were increasing. They all reached to a certain level except protein content.3. During stratification, shell permeability was the main factor that affects the germination of seeds while shell and moisture were less important. The germination rate could be increased by removing or cracking the seed shell, and seed shell removal could significantly shorten the time of stratification. Moisture was the main factor that affected the germination of seeds after removing shell and coat.4. Respiratory intensity was increasing during dormancy breaking, and the total content of water first increased, then remained stable, and then increased again. The content of free water and bound water was generally fluctuating uptrend. On the contrary, fat content was decreasing. Sugars and starch contents were fluctuating, protein content increased dramatically at first and then decreased rapidly after a period of fluctuating. They all participated in the metabolism of preparation for germination.5. By studying other dormancy breaking treatments we found that the germination rate of seeds that were removed seed coat completely was highest, reaching38.89%and31.11%respectively. Seed coat inhibited seed from going through stratification by the mechanical resistance, which was not obvious for seeds at chilling treatment.The germination rate was the highest which could reach to30%after the seeds were cold treated for60days then soaking into GA3at the concentration of150ppm and200ppm. And with the soaking time increasing, the germination rate was decreasing. The seed germination rate was only5%after soaked into150ppm GA3for7days. The best concentration of GA3for seeds without going through stratification was50ppm and the germination rate could reach to13.33%. In conclusion, the suitable concentration of GA3could improve the germination rate.The germination rate reached to36.67%after the seeds were cold treated and soaked into water for5days. The germination rate of seeds without going through stratification reached to3.33%after soaked into water for7days. So soaking seeds into water could increases germination rate.