Effect of different phosphorus concentrations on fennel plant growth, essential oil contents and components (Foeniculum vulgare Mill)

The effects of different phosphorus concentrations on the fennel plant growth, essential oil content and components were studied by using the method of solution culture and making Japanese garden formula's phosphorus content as 1P, and designing 1/8P, 1/4P, 1/2P, 1P and 2P treatments, to reveal the response characteristics and the internal correlation of plant growth and essential oil accumulation to phosphorus concentrations. The results show that the plant height, branch number, inflorescence number, number of nodes, shoot fresh weight (F. W), root fresh weight, and fresh and dry weight (D. W) of the whole plant are higher than other treatments in 1P treatment, and inflorescence number, shoot fresh weight, and fresh and dry weight of the whole plant are significantly higher than other treatments in 1P. With increasing phosphorus concentration, the root/shoot ratio and dry matter rate increase at first and then decrease, and their maximum values appear both at 1/4P. In the aspect of physiological indexes, with increasing phosphorus concentration, C/N ratio continuously decreases, and the order is as follows: 1/8P > 1/4P > 1/2P > 1P and 2P. Chlorophyll and carotenoid contents at low phosphorus concentration (1/8P and 1/4P) are significantly higher than those at high phosphorus concentration (1/2P, 1P and 2P) without linear relationship between other physiology indexes. The essential oil content and yield of essential oil per plant have a similar change, and the order for the essential oil content is 1/8P > 1P > 1/4P, 1/2P, and 2P, while that of the yield of the essential oil per plant is 1/8P and 1P > 1/4P, 1/2P, and 2P. Correlation analyses show that the total nitrogen content is significantly correlated to the protein nitrogen content, with the total carbon and soluble sugar contents significantly correlated to the C/N ratio, with the protein nitrogen contents, total carbon and soluble sugar contents significantly negative correlated to the C/N ratio, with the total nitrogen contents significantly negative correlated to the C/N ratio, with the essential oil content significantly correlated to the yield of the essential oil per plant, and with the essential oil content and the yield of the essential oil per plant significantly correlated to the total carbon and soluble sugar contents. A total of 23 kinds of components in the essential oil are identified, with no difference in the components of the essential oil among different P concentration treatments. However, except for Estragole, the contents of the other components are significantly different when p