Objective To testify the screening function of stachyose on soil bacteria by investigating the bacterial culture in ammonium stachyose medium. Methods The turbidimetry was used to determine the absorbance of microbial suspension at 600 nm per 2 h under the same initial concentration of the microbial suspension and to draw their growth curves. Results Most of soil bacteria utilized stachyose ineffectively, while only a few of them grown well in ammonium stachyose medium. Conclusion Since the major soil bacteria can not take stachyose fully as their energy resources, the species and quantity of rhizobacteria may decrease largely and only a few that utilized stachyose better can develop vigorously. Those rhizobateria with better utilization of stachyose may multiply so rapidly as potential ones in the rhizosphere of Rehmannia glutinosa that the disequilibrium of soil microorganism appears.

OBJECTIVETo study the dynamic changes of dry material accumulation and platycodin D content in Platycodon grandiflorum in different planting densities.

METHODFive different planting densities M1 (4 cm x 25 cm), M2 (6 cm x 25 cm), M3 (8 cm x 25 cm), M4 (10 cm x 25 cm) and M5 (12 cm x 25 cm) were designed in the plot experiment. The individual and colony biomass accumulation, dry material distribution, root yield and platycodin D content were measured in different stage.

RESULTIn a certain density range the individual biomass in P. grandiflorum obviously declined with increasing density with the exception of biomass M2 > biomass M3. On the contrary, the colony biomass increased with the increasing density. Dry material accumulation in each organ in P. grandiflorum in different planting densities showed significance (P<0.05). The dry material distribution in organs in the different planting densities showed significance (P<0.05), and the dry material distribution in flower and fruit reached the minimal level in M2, in the same planting density the distribution in root reached the maximal; The dry material in stem, flower and fruit obviously declined with the increasing density, while the dry material in leaf increased. The individual root output increased with the increasing density, and it reached the highest in M2. The colony root yield increased with the increasing density. The platycodin D content in P. grandiflorum reached the highest in M2.

CONCLUSIONThe result showed that a suitable planting density is very important to P. grandiflorum dry material accumulation and distribution, root yield, platycodin D content and colony yield.

Plant Structures ; growth & development ; metabolism ; Platycodon ; growth & development ; metabolism ; Saponins ; metabolism ; Seasons ; Triterpenes ; metabolism