| Platycodon grandiflorum is a traditional Chinese herb plant, its root has been used for centuries to treat diseases, and has extensive pharmacological effects. While quantity need for this herb increased and wild resource dropped off year after year, the planting area was added, but there existed severity farrago in cultivate regions. In this study, the hereditary diversity of eighteen germplasms from eleven provinces was analysised by agronomic characters, physiological traits, yield and quality method. These results can be used for breeding optimun varieties. Understanding the requirement characteristic of P.grandiflorum for nutrients and the effects of reproductive growth on the yield and quality, which is important for the cultivar of P.grandiflorum. The results are as follows:1. Establishing firstly screening criteria of excellent seeding and germplasms of P.grandiflorum. The screening criteria of excellent one-year seeding was as follows: steam diameter exceeds 3.0 mm, leaf thickness is within 360-370μm, leaf area per plant exceeds 210 cm2, and the excellent seeding come from Shandongzibo, Anhuibozhou, Shandongtaishan, Shandonglinyi, Beijing. According to function, two-year excellent germplasm of P. grandiflorum was divided into edible and medicinal use. Germplasm of P. grandiflorum coming from Neimengchifeng, Shandongzibo, Huhehaote contained the content of total saponin and saponin-D less than 6.0% and 2.0 mg.g-1 respectively, and the content of soluble protein and sugar higher than 3.0%, 50% respectively, they were suitable to edible exploitation. Germplasm of P. grandiflorum coming from Abhuibozhou, Shandonglinyi, Jilinlongjing contained the content of total saponin and saponin-D higher than 6.0% and 3.0 mg.g-1 ,respectively, they were suitable to edible exploitation.2. There existed significant or high significant positive correlation between one-year old plant and two-year old plant among leaf thickness, branches, leaf area per plant, root length, root branches and root fresh weight. Leaf area per plant of one-year old plant significant or high significant positively correlated with root diameter, root length, root fresh weight of two-year old plant; there existed significant or high significant positively correlated between leaf thickness of one-year old plant with root length of two-year old plant, and root fresh weight of one-year old plant with steam diameter, leaf length, root diameter, root length, root fresh weight of two-year old plant. There existed significant correlation of protein, total saponin between one-year and two-year old plant. The agronomic characters and quality of two-year old plant can be predicted by analyzing the agronomic characters and main components of one-year old plant. By using the relationship between main characters within one and two year plant of P. grandiflorum, we firstly set up new prediction method, which could short the period required for screening excellent germplasm of P. grandiflorum.3. Using clustering analysis we definituded the relationship between germplasm diversity of P.grandiflorum with environmental conditions and artificial selection. Clustering analysis showed that cultivated germplasms from Neimeng, Jilin, Liaoning. Beijing, Henan, Zhejiang took together for one class, indicating germplasm resources in different regions exchanged frequently. Geremplasms from Shandongzibo, Anhuibozhou, Shanxishangluo separated respectively, proclaiming P. grandiflorum existed significantly regional disparity. Germplasm resources from Shandonglinyi and Shandongtaishan gather to one class, showing the obvious effect of artificial selection on the germplasm differentiation.4. Clearing and definiting preliminary the rule of dry matter accumulation and absorption of NPK of the white and the purple. Dry matter accumulation of P. grandiflorum during the whole growth stage showed slow-fast-slow tendency. The dry matter accumulation in the puple was higher than the white, there was difference of the dry matter accumulation order in different organ, the white was stem > root >leaf >flower and fruit, the puple was stem > root >flower and fruit > leaf . Root dry matter accumulation ratio in white was greater than the puple, and was less than the puple in flower and fruit, which illustrated that there was variety in differentNPK uptake of the puple and white during the whole growth stage was N>K>P, NPK uptake ratio in the white was 1:0.51:0.95, and was 1:0.28:0.51 in the puple, PK uptake ratio was higher in the white than in the puple. NK accumulation ratio in root was higher in the white than in the puple, P accumulation ratio in the white was lower than in the puple during the early stage, and higher than the puple during the late stage, NPK accumulation in flower and fruit was lower in the white than in the puple during the experiment, which illustrating variety between different germplasm of P. grandiflourm.5. Ascertaining first the resource of carbohydrate needed by flowering through the studies on content changes of carbohydrate in different organs during flowering, and the effects on flowering on the yield and quantity of P. grandiflorum, which laid the theoretical foundation for the flowering regulation and increased the yield and quantity of P. grandiflorum. The starch and soluble sugar contents in root of the white and puple plant continued to decline, while they remained slowly rising trend in root of the deflowering plant from deflowering day. The root starch content in the white was higher than in the puple, and the soluble sugar content was lower in the white than in the puple. The trends of starch and soluble sugar content in stem were similar in the white and the puple, the differences of starch and soluble sugar content between flower and deflower plant were higher in the puple than in the white. During flowering, the starch content in leaves of flower and deflower plant of the white was higher than the puple, and the starch content in leaves of deflower plant was higher than the flower plant in both the white and the puple. The starch content in deflower plant of the puple was lower than the flower plant except the 5th day and 20th day. There was no significant differences in the white between the flower and deflower plant, while soluble sugar content in deflower leaves was significantly higher than in flower leaves in the puple plant, which clearing the need of carbohydrate in the puple plant was more than the white during flowering.6. Establishing control measures suitable to the cultivation of P. grandiflorum. The root appearance quality and main component contents of deflower treatment were better than defruit and CK treatments, deapexing was of no advantage to promote root yield and quality. The highest yield was deflowering, the second was defruiting. The yields treated by Ethephon was superior than treated by ethephon-cycocel. The optimum treatment in both the puple and the white was 0.07% ethephon.
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