药材的道地性是指中药的基源来自于一些特殊的居群，所含的化学成分含量较高或各种成分比例合理而导致药效较好，也即植物种内发生了化学分化，产生了不同的化学宗。化学宗的形成可能是中药道地性形成的基础，对药用植物化学宗的研究有利于阐明中药道地性形成的原因。化学宗的形成是次生代谢产物代谢途径中关键酶基因和环境因素共同作用的结果。大黄是重要的常用大宗药材，其原植物（药用大黄、掌叶大黄和唐古特大黄）是研究药材道地性形成的理想材料。我们前期的研究结果表明这三个种应被归并为同一个种，种内分化并非形态学上的而是化学上的，即已经形成了化学宗，蒽醌类含量高的化学宗与道地产区相吻合。因此，本项目拟以大黄原植物的居群为研究单元，从其主要药效成分入手，结合主要药效成分代谢途径的关键酶基因和环境因子，综合探讨大黄道地性形成的原因。本项目的完成不仅能够解释中药大黄道地性形成的机制，也为同类型药材及化学分化的研究提供借鉴。

Geoherbalism of medicinal materials refers to the medicinal efficacy of Chinese medicine from some special populations (i.e. the source of Chinese medicine) is higher than that from other populations. Higher efficacy of geoherb attributes to the higher content of chemical components or a certain ratio of different components. Geoherbalism also means the chemical differentiation between populations within a source plant species, and forms the different chemical races. The formation of chemical race may be the foundation of the geoherbalism formation of Chinese medicine. Study on the chemical race of medicinal plant can facilitate to clarify the cause of geoherbalism formation of Chinese medicine. The formation of chemical race is the result of the interaction of key enzyme genes in the pathway of the secondary metabolites and environmental factors. Rhubarb is an important bulk medicinal material, and its source plants (Rheum officinale, R. palmatum and R. tanguticum) are ideal candidates for studying geoherbalism formation. Our previous studies indicated that these three 'species' should be merged into one species. Species differentiation is not morphological but chemical, which means rhubarb have formed different chemical races. The chemical race with high content of anthraquinones accords with the geo-authentic producing area of rhubarb. In this project, based on the sampling at population level, the major medicinal components, the key enzyme genes in the biosynthetic pathway of the major medicinal components and environmental factors from the distribution of the source plants of rhubarb will be analyzed. We attempt to explore the causes of the geoherbalism formation of rhubarb. The findings of the present subject would not only explain the mechanism of the geoherbalism formation of rhubarb, but also provide valuable references for studying chemical differentiation and the similar Chinese medicinal materials.