Abstract: The diurnal variation of photosynthesis for the leaves of two different Houttuyniae chemotypes at different growth stages had been studied under the natural conditions, as well as their volatile chemical constituents were separated and identified by GC-MS. The results were as follows: The curve of diurnal variations of net photosynthetic rate (Pn) tended to be typical “single peak” type at seedling stage and “double peak” type at flowering stage. Tr diurnal variation curve of both stage s were “single peak” type. The numbers of chemical constituent were much more in Myrcene chemotype’s and at seedling stage than those in Decanal chemotype’s at flowering stage, respectively. However, the total contents of common and major chemical constituent were lower in Myrcene chemotype’s and at seedling stage than those in Decanal chemotype’s at flowering stage, respectively. Furthermore, there were extremely significant differences among some major chemical constituents in different accessions at different growth stages. In conclusion, different Houttuyniae chemotypes at different growth stages showed certain differences on photosynthesis and volatile chemical constituents. The result also indicated that there were no significant difference between Houttuynia emeiensis and Houttuynia cordata in both photosynthesis and their volatile chemical constituents.

Key words: Houttuyniae, chemotype, growth stage, net photosynthesis, volatile chemical constituents