| The camphor tree (Cinnamomum camphora) is one of the most important landscape trees used for improving city environments. It is a evergreen arbor belonging to the family Lauraceae, with beautiful shape, large and dense crown, wide adaptability and resistance to environmental pollution. It also can absorb many kinds of noxious gases. However, the dropping of its fruit is seriously polluting the city environment and also cause inconvenience to pedestrians because of the huge amount of camphor tree fruit, thus limiting the application of camphor trees in the garden. To cultivate a sterile triploid is an effective way to solve this problem, which requires a tetraploid Camphor being induced first, then cross with a diploid camphor tree to get sterile camphor tree. The purpose of this study is for the breeding of tetraploid camphor tree.In this study, different in vivo and in vitro materials of camphor tree were treated with different colchicine concentrations for different time. Then identify the ploidy through the size of stomas and the number of chromosome. The tetraploid camphor tree is successfully induced for the first time. Finally, plants of diploid and tetraploid were observed and compared morphologically. The results are as follows:1. Different in vivo materials of camphor tree were treated with colchicine solution, which indicated that soaking seed is a better method. Tetraploid plants were successfully induced in 9 of all 10 treatments. In the treatment of 0.8%,48h and 1.0%,48h, the induction rate was 22.0% and 20.6%, and 11 and 7 tetraploid plants were obtained, respectively. The shoot tips of seedlings were treated with colchicine solutions of 0.2%-1.0% for 2h or 4h, but the survived plants have not been identified as tetraploid.2. In the induction experiments of in vitro materials, shoot tips of the line "L14" were treated with colchicine solutions, and then hardened and transplanted to the soil after rooting. The results showed that the most suitable transplanting medium were perlite, with the survival rate of 65%, while the survival rate in media with peat were zero. In the survived plants, only one individual from the treatment of 0.2%,2d has been successfully doubled. When treated with liquid medium containing colchicine, only the primary embryos of 0.5%,3d and 1.0%,3d and 0.5%,6d differentiated into 4 and land seedlings, respectively. This five seedlings, however, did not survive in the subculture. Shoot tips, callus and somatic embryos treated with colchicine in solid medium did not differentiate any seedlings. 3. Before identifying the ploidy through the stoma size of leaves, the impact of two sampling methods and leaf size on the stoma size was investigated. The results showed that there are significant differences between different sampling methods and leaf size. About 32 putative tetraploid plants were selected through measuring the stoma size of 707 colchicine-treated seedlings. The number of chromosome is observed further for these plants, which confirmed the successful doubling of chromosome.4. The methods of chromosome counting were explored, indicating that dissociation for 10 min followed by staining with the Carbol fuchsin D solution is better. The root tip is more suitable material for chromosome counting in contrast to shoot tip.5. The plants with diploid and tetraploid are observed morphologically. The results showed that the height of tetraploid plants was lower, along with less-lateral branches, shorter internode of main stem, deeper color and rougher surface of leaves, and rich of aroma. While the stem diameter, leaf length, width and thicknesses, and petiole length and thicknesses of tetraploids did not change significantly. |
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