[Effects of phosphorus fertilizer on the root system and its relationship with the aboveground part of flue-cured tobacco].

Using 'Yuyan 10' as the material, the effects of different phosphorus fertilizer application on root characteristics of tobacco, such as root dry mass and the difference of dry matter distribution and mineral nutrient accumulation between its above and underground parts were investigated. The results showed that the growth of flue-cured tobacco root system and the distribution of dry matter to the aboveground part were significantly promoted by phosphorus fertilizer application. The application of 30 kg P2O5 · hm(-2) led to the maximums of root dry mass, root volume, root activity and the minimum of root to shoot ratio. The maximum nutrient accumulation rates of root and leaf appeared 57-66 days after transplanting and 44-55 days after transplanting, respectively. Phosphorus could not only promote the mineral nutrition absorption of tobacco and the earlier appearance of maximum nutrient accumulation, but significantly promote the nutrient accumulation of the aboveground part. But, the positive effects described above would be weakened when the amount of phosphorus fertilizer was more than 30 kg P2O5 · hm(-2). Therefore, it's necessary to control the amount of phosphorus application to improve the quality of tobacco leaves.

[Analysis of RAPD on medicinal plants of Codonopsis pilosula].

OBJECTIVE: To study genetic diversity and genetic relationship among 9 cultivated and 4 nature populations of Codonopsis pilosula and C. pilosula var. modesta form Gansu Province at DNA level. METHODS: DNA of 217 individuals was amplified by 14 decamer primers from 200 radom primers. The polymorphic bands of RAPD were counted. And the results were analyzed by clustering analysis NTSYS-PC software. RESULTS: A total of 125 loci were detected by 14 arbitrary primers, among which 109 and 106 loci were polymorphic in C. pilosula and C. pilosula var. modesta respectively, and the percentage of polymorphic bands (PPB) were 87.20% and 84. 80%. The cluster analysis showed that 13 populations were divided into 2 groups. The one included 8 cultivated populations of C. pilosula, the other group consisted of a cultivated population and 4 nature populations of C. pilosula var. modesta. CONCLUSION: The RAPD results indicated that there was abundant genetic diversity in cultivated populations of C. pilosula and C. pilosula var. modesta. The genetic differentiation among 8 cultivated populations of C. pilosula was very small and related to their geographical distance. Only the cultivation in Wen County originated from C. pilosula var. modesta, while the other populations cultivated in Gansu Province belongs to C. pilosula.