Three Ligularia species (L. tongolensis, L. cymbulifera, and L. atroviolacea) were examined with respect to the chemical composition and nucleotide sequence. Furanoeremophilanes were found to be produced in the root of all samples of the three species collected in northwest Yunnan and southwest Sichuan. Eight furanoeremophilanes were identified, two of which were new. Most of the identified furanoeremophilanes were oxygenated at 3, 6, and 15-positions. The nucleotide sequence of the atpB-rbcL intergenic region was found to be essentially the same in the three species. These similarities imply that the three Ligularia species, all belonging to the section Corymbosae, are close to one another. The intra-specific diversity in the two widely distributed species in the Hengduan Mountains area, L. tongolensis and L. cymbulifera, were in contrast. Four out of 19 L. tongolensis samples contained a strongly Ehrlich-positive compound besides a number of positive compounds, and five variants of the atpB-rbcL sequence were found in these samples. In contrast, no variation was observed in 13 L. cymbulifera samples with respect to the furanoeremophilane composition or the atpB-rbcL sequence. The lack of diversity in L. cymbulifera probably resulted from the uniformity of its habitat.
Himalayan snowball plants, which are considered to be an extreme form of downy plants, have very dense trichomes on well-developed bracts that surround the inflorescences. It has been postulated that the downy inflorescences of these plants might serve to keep the interior of inflorescences warmer than the outside and, thus, to protect reproductive cells from low temperatures in their Himalayan habitat. In the present study, we examined the downy inflorescences of Saussurea medusaMaxim. in native habitats in the high alpine zone of the Henduan Mountains in Yunnan, China, and we analyzed the temperature within inflorescences after absorbance of light energy. S. medusais pollinated by bumblebees and we found that its inflorescences accumulated heat not on the inside, but, rather, on the upper surfaces. The thick hollow stems and the overlapping bracts with obvious epinasty might serve not only to retain heat, but also as an insulator to protect the inside against overheating, with apparent local warming of flowers that are located at the tops of plants, which are cone-shaped. We made a model that mimicked the warming of inflorescences, providing support for the hypothesis that the downy bracts of S. medusahave two functions: thermal insulation to protect the inside of flowers and the accumulation of heat on the upper surfaces of the inflorescence. Such a system might be effective in attracting pollinators and also in protecting tissues from extreme variations in temperature.
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