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Background: Because of the certain overlapping of the genus Bupleurum, the identification features are few and the delimitation among species is difficult, Bupleurum taxonomy is under frequent revisions. In this research, hierarchical cluster analysis based on morphology characters is done to establish a dendrogram and illustrate the taxonomic relationship among Bupleurum species (Apiaceae) from China. Materials and Methods: The fruit morphology of 17 Bupleurum taxa from China was investigated with a scanning electron microscope (SEM) and optical microscopy (OM). The hierarchical cluster analysis based on 41 morphological character states belonging to 9 characters was done to establish a dendrogram and illustrate the taxonomic relationship among the studied species of Bupleurum (Apiaceae) from China. Results: Based on fruit morphological characteristics, it is possible to separate the Bupleurum species into the following four groups. The research indicates that the classification of Bupleurum in China is closely related to geographical distribution, which is divided into Southwestern and Northeastern Bupleurum. Conclusion: The fruit morphological characteristics are variable enough to distinguish species between Bupleurum, such as fruit length, width, shape, colour, the curvature of the outer periclinal and so on in this article. Morphological characters could be probably the taxonomical standard of intraspecific and interspecific delamination, which is significant for understanding the classification of Bupleurum. [ABSTRACT FROM AUTHOR]

Phosphorus (P) deficiency affects plant yield and quality, yet at the same time, excessive phosphorus application does not necessarily promote the growth of plants. How to maintain a balance between biomass accumulation and phosphorus application is a problem. Therefore, the purpose of this research was to explore the relationship between yield and quality of Bupleurum and phosphorus fertilization, based on three phosphorus fertilization levels (20 kg∙ha−1; 10 kg∙ha−1; and 0 kg∙ha−1). We adopted gas chromatography-mass spectrometry to assess the response of primary metabolites of different plant tissues (flowers, main shoots, lateral shoots and roots) to phosphorus fertilization. At the same time, high-performance liquid chromatography was used to quantify saikosaponin A and saikosaponin D, the main active ingredients of Bupleurum. Our research showed that low phosphorus level application has a positive impact on the yield and quality of Bupleurum, especially the above-ground parts increasing the fresh weight of flowers and lateral shoots and the length of main shoots, and moreover, increasing the saikosaponins content in all above-ground parts while decreasing the content in roots which show no significance increase in fresh weight and length. However, high phosphorus level showed a negative impact as it decreases the saikosaponins content significantly in flowers and roots. Furthermore, phosphorus application changed the proportion of saikosaponins, promoting the content of saikosaponin A and inhibiting the content of saikosaponin D in most organs of Bupleurum. Therefore, we can say that high phosphorus application is not preferable to the yield and quality of Bupleurum. To identify the metabolic pathways and special key metabolites, a total of 73 metabolites were discovered, and four differential metabolites—ether, glycerol, chlorogenic and L-rhamnose—were considered to be the key metabolites of Bupleurum's response to phosphorus fertilization. Furthermore, Bupleurum's response to phosphorus fertilization was mainly related to metabolic pathways, such as starch and sucrose metabolism and galactose metabolism. Under the phosphorus level, the content of sugars, organic acids and their derivatives, polyols and their derivatives and alkyl were upregulated in flowers. Furthermore, the contents of compounds in the main shoot and lateral shoots showed the same upward trend, except glycosides and polyols and their derivatives. [ABSTRACT FROM AUTHOR]

Bupleurum (Apiaceae) is widely used in traditional Chinese medicine to treat inflammatory and infectious diseases. Although roots are the only used parts in China, other countries use the whole plant. The yield and quality of Bupleurum depend mainly on fertilizers, especially nitrogen. The current study aimed to assess the relationship between the nitrogen fertilization level and the quality and metabolomic response of different parts (flowers, main shoots, lateral shoots and roots) of Bupleurum to three nitrogen fertilization levels (control group: 0 kg·ha−1; low-nitrogen group: 55 kg·ha−1; high-nitrogen group: 110 kg·ha−1). The results showed that a high nitrogen level increases Bupleurum yield and quality parameters only in aerial parts, especially flowers, but has no significant effect on roots. The HPLC method was exploited for simultaneous quantification of three saikosaponins (A, C and D), which are the main bioactive components in the plant. It was found that the total content of saikosaponins decreased with high nitrogen fertilization in roots but significantly increased in flowers. Moreover, nitrogen fertilizer promoted the content of saikosaponin A but inhibited saikosaponins C and saikosaponins D in most parts of the plant. To study the response of primary metabolites, we adopted gas chromatography–mass spectrometry (GC−MS) analysis; 84 metabolites were identified that were mostly up-regulated with a high nitrogen level in flowers but down-regulated in roots. Four differential metabolites—D-fructose, lactose, ether and glycerol—were recognized as key metabolites in Bupleurum under nitrogen fertilization. Meanwhile, The Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment results explained that the impact of nitrogen fertilization on Bupleurum was attributed to the C-metabolism, N-metabolism, and lipids metabolism. This research put forward new insights into potential mechanisms and the relationship between the quality and yield of Bupleurum and nitrogen fertilization. [ABSTRACT FROM AUTHOR]