Studies On Polyploid Induction Of Caragana. Intermedia By Colchicine

Caragana is a genus of about 100 species of machaka in the family Fabaceae,native to the arid and semi-arid lands of Europe and Asia. It provides important ecological functions, such as stabilization of sands and conservation of water and soil. Caragana species are oil tree plants and can be used as food plants, green manure and firewood etc. Besides, Caragana is ornamental plant, can widespread use at hedgerow and afforest,which are very importance at the northern part of our country. Polyploid plays a very important role at the evolution of higher plants, due to the accumulation effect of multiple chromosome set,the content of biochemical component rising and result in the characteristics of organic tremendous, such as big flowers, leaves and fruit, which can enhance their environmental adaptability and adversities. Polyploidy breeding has also become the main breeding method of enhancing garden and ornamental plant characteristics, for instance, plant size, leaf thickness, leaf aspect ratio and flower size etc. using the colchicine as mutagen of chromosome doubling has already succeed in various plants such as Citrus, Robinia and Alocasia. At present, there is a few reports about Caragana research and not report of research on polyploid breeding at domestic and overseas. This experiment uses colchicine as main inductive medicament, through soaking seeds, packaging seedlings and soaking invitro seedlings and soon the method to induce seeds, buds and seedlings of Caragana intermedia. The auther expected to find out a suitable inductive method to have the polyploid and to lay certain foundation for Caragana's polyploid breeding. The results of this experment as follows:1. In two different stages of the colchicine processing Caragana intermedia seeding:â‘ Soaking seeds derectly by colchicine, the optimum treatment was 0.3% colchicine solution for 48 h, and the rates of mutation plants and tetraploid plants were 53.3% and 20%, respectively;â‘¡Soaking after 12 h seeds germinating, the optimum treatment was 0.15% colchicine solution for 36 h, and the rates of mutation plants and tetraploid plants were 73.3% and 23.3%, respectively.2. Treating the apical portion of seedling with different dilute solution of colchicines, as the concentration of colchicine increasing, the treatment seedling's mortality rate increase accordingly and the trend of mutation rate increased at first then declined. The optimum treatment was 0.6% colchicine solution for 6d, and the rates of mortality and mutation plants were 50% and 16.7%, respectively. But we had not discovered the polyploid.3. In the colchicine processing invitro seedling, the optimum treatment was 0.1% colchicine solution for 36 h, and the rates of mutation plants and tetraploid plants were 20% and 6.7%, however, the rates of mortality was 63.3%.4. The method of soaking invitro seedlings are worse than soaking seeds, but better than treating the apical portion of seedling. Through the method of soaking seeds, we can induced more polyploidy than from soaking invitro seedlings, but, treating the apical portion of seedlings failed to obtain any polyploidy.5. Chromosome observation found that the chromosome number of mutated plants was 2n=4x=32(tetraploid),while that of the control plants(diploid) was 2n=2x=16. The aneuploid and Chimera was also found among treatment plants. The natural mutation rate of Caragana intermedia is low and chromosome observation of more than two thousand seedling plants found that there are two chromosomes were easy to be broke among chromosome flaking process, furthermore, a few plant cells have B chromosome.6. The polyploid mutation compares with its diploid had obvious differences, the concrete manifestation was that laminae thickens, the color of leaves for the changes depth, the difference of the stoma size and stoma density between the Caragana polyploid and the diploid is remarkable, as well as the chloroplast number.7. At the experiment of soaking seeds, we also obtained a triploid and the chromosome number was 2n=3x=24. This triploid seedling not only grew very slowly but also the blade was serious deformaty. Furthermore, the triploid comparing with its tetraploid and diploid showed that the characteristics of triploid is bigger stoma size, small stoma density and more chloroplast number.