The objective of this study is to analyze the effects on the growth and on the proportion of components of Bupleurum kaoi Liu. (B. kaoi) under the fertilizations of six different concentration rates of nitrogen. B. kaoi is a perennial herb native to Taiwan, and its roots are used for herbal medicines. The fertilizer of Hoagland solution was applied to B. kaoi plants only one time per week. Six different Hoagland solutions contained different amounts of NH4NO3: 0, 2, 4, 10, 16 and 22 mM. Also, the dry mass production and the proportion of components in the roots were recorded. The analysis of components of B. kaoi was conducted by using five types of Saikosaponins (SS): a, b1, b2, c and d. Turning to the growth and the property of dry mass production, the result demonstrated that the growth and the property tended to increase at the value above 10 mM in terms of the length of the plant, the numbers of leaf, and SPAD. Similarly, the dry mass of the plant both above and underground increased at the value over 10 mM. During the late growth stage, the growth underground continued at the value above 10 mM. By contrast, in the area in which the overall value was above 10 mM, there was no significant differences between growth and dry mass production. Also, the growth and the property of dry mass production were substantially high at the value above 16 mM in the analysis using the main types of Saikosaponins: SSa, and SSd, whereas the rate of components and the total amount of Saikosaponins elevated at the value above 10 mM with Sb1, SSb2, and SSc. From these results, the concentration rate over 10 mM of nitrogen in fertilizer, the proportion of components in the roots of B. kaoi attained its saturation point; therefore, the value of 10 mM could be the optimal nitrogen concentration for fertilizer.
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