The Response Mechanisms Of Root Growth To Phosphorus Stress And Auxin Treatment In Tobacco

Three tobacco varieties (K326, xiangyan4, yunyan87) were used in this study, to select the best phosphorus (P) application level and treatment time for the root growth in tobacco; and to inspect the best auxin application level and treatment time for the root growth in tobacco; and these technology will be used to the tobacco field production, achieved a P stress and auxin treatment technology for the tobacco root growth and supplied the scientific theory for the other crops.1. Results of phosphorus treatment showed that,0.02 mmol/L of P concentrations in plant culture solution is better for tobacco root growth at earlier seedling stage; but 0.1 mmol/L of P concentrations in plant culture solution is better for tobacco root growth at later seedling stage. These results suggested that tobacco root growth can be accelerated by the P stress and auxin treatment in plant culture solution.2. The root development and shoot growth in tobacco plant tissues can be accelerated by the P stress condition in plant culture solution at the later seedling stage or harvesting stage (80-100 days after transplanting, harvesting stage). The lateral root number, total root length, root activity, root shoot ratio and root biomass were increased under the P stress condition, but main root length was decreased.3. The effects of different P stress on nutrients uptake activity in root showed that, the nutrients uptake activity in root can be significantly increased by P stress, and then higher amount of nutrients were uptake, and benefit for tobacco root development, this is the nutrients basis for initial root development in tobacco under the P stress conditions.4. The lateral root growth can be affected by auxin treatment, but the main root development cannot be influenced by the auxin treatment, the effect of auxin treatment (120 μmol/L) time on the lateral root growth are different. The lateral root number, total root length, root activity, root shoot ratio and root biomass were increased under the auxin treatment, the better efficiency with auxin treatment 5,12, 24 h. Auxin treatment (120 μmol/L) with 12 h is best for the root development in tobacco.5. RSI-1 gene in tobacco plays an important role for root development, the relative expression of RSI-1 gene is the highest under the auxin treatment (120 μmol/L) with 5 h, and then the expression was down-regulated by the auxin treatment with the longer treatment time. These results suggested that the response of gene expression is faster than what was found in lateral root response.6. The root development and shoot growth of tobacco can be significantly accelerated by the P stress and auxin treatment.0.1 mmol/L P stress treatment with 2 days is best for the lateral root development in tobacco, and 120μmol/L auxin treatment with 12 h is best benefit for the root development, and following treatment will be 5 and 24 h treatment.