The Research Of Method Of Promoting Bunge Hackbeery Seeds Germination

As one of the rare garden species, bunge hackbeery, a celtis plant of Ulmaceae, boasts of its high value both in application and economy and is deemed as one of the most promising tree species. However, the deep dormancy of bunge hackbeery seed has resulted in difficult sprouting and low germination rate, thus bringing considerable inconvenience to forestry production and making it difficult for bunge hackbeery to be promoted in various regions in Northeast China.In this thesis, different kinds of medicament were used to soak the bunge hackbeery seeds with different treatment of temperature and illumination time so as to observe the germination of bunge hackbeery seeds. Different storage methods were applied to preserve bunge hackbeery seeds. Both coated and conventional sowing methods were employed for comparison. Besides, the impact of factors, such as storage time and method, broken shell treatment, illumination treatment, water, and chemical treatment, on seed germination was studied to explore the characteristics of bunge hackbeery seed dormancy and germination. The major results findings of this thesis are given as follows:1. Bunge hackbeery seed dormancy is a result of the interaction between exogenous dormancy and endogenous dormancy. Concentrated sulfuric acid with a concentration of 98% was used to soak the seeds for 30 minutes, by which the mechanical and permeability barriers resulted from seed coat could be effectively eliminated. However, the use of concentrated sulfuric acid alone failed to break the dormancy of bunge hackbeery seeds since it didn’t germinate after treatment.2. Seed dormancy could be broken by soaking with GA3 based on concentrated sulfuric acid treatment. Bunge hackbeery seed’s germination rate turned out to be the highest when GA3 concentration reached 400 mg.L-1,the germination rate reached to 27.7%; while it appeared a decreasing trend once GA3 concentration approached 600 mg.L-1, which suggested that bunge hackbeery seed’s germination rate didn’t always rise in proportion to GA3 concentration. In addition, the use of naphthylacetic acid in bunge hackbeery seed soaking was also be able to break seed dormancy, with limited effect though. Impact of cytokinin soaking treatment on bunge hackbeery seed’s germination rate was extremely faint. That figure was only 1.7%.3. Having undergone seed soaking with concentrated sulfuric acid and GA3, the seeds received illumination treatment at different times. It was found that bunge hackbeery seed’s germination rate in darkness was higher than that exposed to light and germination rate declined as illumination time increased, seed emergence rate in 24h illumination was 21.4% lower than that in 0h illumination, which indicated that light played an inhibiting effect on bunge hackbeery seed’s germination, and that these seeds were light inhibited.4. Bunge hackbeery seeds did not readily to germinate at a constant temperature. Seed germination rate was improved with diurnal changed temperature (0℃ 12h+25℃ 12h), especially after the seeds were stored at a low temperature for a while. During the trial, seeds that were treated by diurnal changed temperature after undergoing 120-day cold storage showed highest emergence rate, which was 57.5%.5. Cold stratification was conducive to the germination rate of bunge hackbeery seed. Seeds sown after undergoing 120-day cold stratification showed favorable germination effect. Comprehensive stratification had better effect compared to natural stratification. In winter, sowing cost would be reduced if bunge hackbeery seeds were sown after being stratified for a period of time, which was a favorable choice for forestry production. The optimum germination temperature of bunge hackbeery seeds lay between 25℃ and 30℃.6. Bunge hackbeery seeds failed to germinate with dry storage, suggesting that it was improper to dry store bunge hackbeery seeds with high safety moisture content. Moreover, bunge hackbeery seeds didn’t germinate with wet storage in room temperature but germinated with wet storage in low temperature. Therefore, the optimum storage method for bunge hackbeery seeds was wet storage in low temperature.7. Coated sowing method was able to promote bunge hackbeery seeds to germinate with a higher rate compared to conventional sowing methods. Seed emergence time with this method was also ahead of that with conventional sowing methods. But in order to promote seed emergence, it’s better to treat the seeds with medicament soaking or comprehensive stratification before coating. Seed emergence rate was 63.3% when coated sowing methods was carried out after the seeds underwent 120-day comprehensive stratification. Within an identical time (120d), the emergence rate by this method was 63.3% higher than that by direct sowing method that was widely applied in current forestry production. This was also the highest emergence rate that was observed by the experimental study of this thesis.