Effects Of Sowing Time, Water And Fertilization On Growth And Physiological Characteristics Of Platycodon Grandiflorum

The seedlings of Platycodon grandiflorum collected from the different sowing time were used as experiment materials. The plant height, basal diameter, crown width, leaf area, Pn, Cond, Ci, Tr, Fo, Fv/Fm, qP, qN, fresh weight, fPro, soluble sugar, MDA, soluble protein, ground growth, underground growth, economic yield and biomass yield of natural environment and fertilization were measured. And then, the growth and physiological characteristics were analyzed. The proper sowing time of P. grandiflorum was determined. The optimum fertilization scheme under different sowing time of P. grandiflorum was obtained. In addition, pot experiment was conducted to study effects of water stress on photosynthetic, fluorescence and physiological characteristics, to investigate the mechanism of drought resistance and to compare the drought resistance of P. grandiflorum sowing in different time. The main results were as follows:1. During natural growth period, the plant height, basal diameter, crown width and leaf area gradually increased and P. grandiflorum sowing in autumn was significantly higher than sowing in spring. In the whole day, Pn, Cond and qN dropped after the first rised; Ci and qP was on the contrary. During months, Pn, Cond and qP increased firstly and then decreased; Ci and qN was on the contrary. Photosynthetic and fluorescence parameters of P. grandiflorum sowing in autumn were greater than sowing in spring. Proline and soluble protein content had a downward trend after the first rised, the corresponding values of P. grandiflorum sowing in autumn was higher than sowing in spring. Ground growth, underground growth, economic yield and biological yield of P. grandiflorum sowing in autumn were significantly higher than sowing in spring. Sowing time had effects on the growth and physiological characteristics of P. grandiflorum, P. grandiflorum sowing in autumn had a better performance than sowing in spring.2. During water stress of P. grandiflorum, the trend of Pn was consistent with Ci, there was a significant positive correlation between Pn and Cond, Ci, the stomatal limit was the main reason which casused the decline of Pn. Water stress had a significant effect on the physiological indicators of P. grandiflorum, with water stress intensified, RWC declined, soluble sugar and MDA content increased, SOD and POD activity declined after the first increased. Drought tolerance in P. grandiflorum of different sowing time was evaluated by using subordinate function, the results showed that P. grandiflorum sowing in autumn had stronger drought tolerance.3. Fertilization had significant effects on plant height, basal diameter, crown width, leaf area, Pn, Cond, Ci, Tr, Fo, Fv/Fm, qP, qN, fresh weight, fPro, soluble sugar, MDA, soluble protein, ground growth, underground growth, economic yield and biomass yield. Fertilization increased the growth and yield, enhanced the photosynthetic capacity and physiological characteristics of resilience.4.8 g fertilization ratio of nitrogen, phosphorus and potassium was the optimum fertilization scheme for P. grandiflorum sowing in spring, while 4.8 g organic fertilizer was the optimum fertilization scheme for P. grandiflorum sowing in autumn.