| Summary: | 碩士 === 國立成功大學 === 生命科學系碩博士班 === 97 === Cyperaceae is the large flowering plant family in the world. There are many species growing in wetland and aquatic areas, and their photosynthesis include C3 and C4 pathways, and even have C3-C4 intermediates. It is worth to explore the diversity of the photosynthetic mechanisms of Cyperaceae in plant anatomy, ecology, physiology and evolution of their relation and significance. In this study, photosynthetic pathways of Cyperoideae in Taiwan were recognized by leaves or culms anatomy and stable carbon isotope ratios. Applying ArcGIS and Excel softwares, simple correlation and linear regression analysis were used to investigate the correlations of climatic data and latitude with species percentages, species numbers of different photosynthetic pathways and 3 tribes. All these correlations are displayed by the theme maps. In addition, we also investigated the habitats of Cyperoideae.
The results showed that 49 species, 5 subspecies and 9 varieties displayed C4 pathway, and 22 species, 4 subspecies and 2 varieties belonged to C3 pathway. The C4 percentage was 35.2% of Cyperaceae in Taiwan. It was higher when compared with other regional studies of photosynthetic pathways of Cyperaceae in the world, because Taiwan is located in the subtropical and tropical climate districts. The results of correlation and regression showed that the correlations of the C4 percentage with temperature factors are higher than rainfall factors. It was positively correlated with temperature factors, but not with the rainfall factors. The C4 percentage was not correlated with altitude, due to the small number of independent variable. However, the numbers of C3 and C4 were strongly and negatively correlated with altitude, showing that no matter what types of photosynthesis, Cyperoideae possess tropical and subtropical affinities. The analysis of tribe percentage, Abildgaardieae showed no correlated with any environmental factors, Cypereae was positively correlated with temperature factors, but Scirpeace was negatively correlated. Their coefficients of regression were smaller than that of C4 percentage. Therefore, the climatic factors are much to do with photosynthetic pathways than taxa. And Cypereace is negatively correlated with altitude in line with previous studies.
Most species in Cyperoideae were found in wet and aquatic areas (68.5%). The percentage of C4 plants was lower in wet and aquatic areas (59.7%), but there was 21.9% in mesic areas, compared with the C4 grasses and dicots that tended to be more abundance in arid areas. It appears that water use efficiency is not the key point of C4 evolution in Cyperaceae. On the other hand, C3 pathway adapted to wet and aquatic areas (88.9%). It may explain that the water availability is crucial and suggests C4 plants evolved from C3 pathway in wet and aquatic areas, then gradually have been adapting to different habitats, and differentiation of species.
This research recognizes photosynthetic pathways of Cyperoideae, and preliminary investigates the correlations between Cyperoideae and the environmental factors in Taiwan. More information still need further survey especially the Caricoideae species, and the application of Geographic Information System to establish ecological environmental databases and mathematical models for understanding the effects of environmental factors on the distribution of C3 and C4 pathways.
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