碩士 / 國立中興大學 / 生命科學系所 / 106 / Natural foliar variegated plants are occasionally found in forest understoreys. Pigmental type (chemical color) and structural type (physical color) are two main mechanisms of foliar variegation, have been reported. Some plants keep variegation throughout their life history, some only show this feature at the juvenile stage, and still others display this feature before flowering time. Anti-herbivory and photoprotection are two main hypotheses of the ecological meaning of foliar variegation. Begonia formosana (Begoniaceae), a shade herb native to Taiwan, has variegated and green form in nature. The aims of this study are to: 1) describe morphological differences between green and variegated leaves; 2) elucidate the reproductive differences between variegated and green forms with a view to understanding fitness differences between the two forms; 3) clarify the interaction between variegation and visual herbivores. In this study, adult female grasshopper, Atractomorpha sinensis, is chosen to represent the visual herbivore for understanding the herbivore preference.
The leaf morphological study shows the number of multiseriate unbranched hair, and there is no difference between the two forms. The polygonal-shaped adaxial epidermal cells significantly vary in size. The green area of a variegated leaf has the largest polygonal-shaped adaxial epidermal cells, and the following is the green leaf. The white area of a variegated leaf has the smallest one. There is no size difference between guard cells of different leaf areas, but the green area of a variegated leaf has the smallest subsidiary cells, and the white area of a variegated leaf has the lowest stomatal density. Few druse-form oxalate crystals were found only in the adaxial epidermal cells of the white area of a variegated leaf.
The variegated form of Begonia formosana accounts for around 9% of total population in Qingshan Waterfall Trail area, but the herbivore damage in the variegated leaves is significantly fewer than in the green leaves. This observation support the anti-herbivory hypothesis. In the aspect of the reproductive organs, there is no significant difference in the number of male flowers, female flowers, fruits and seeds between variegated and green form. More detail characteristics, including the size of flower petals, 2D projected stigmata, fruits and the number of anthers also show the same pattern. However, the variegated form has significantly wider pollen grains and bigger seeds than the green form. This reproductive difference may reflect higher photosynthetic reserves in the variegated form potentially due to lower herbivory on the variegated plant, allowing it to produce larger pollen grains and seeds.
The genome size between the variegated and green form showed no difference. The variegated form showed the leaf plasticity in the high and low light environment. Some variegated form individuals grew green leaves in the high and low light environment. The variegated and green form are different for the visual herbivores. The grasshoppers stayed significantly longer and caused larger damage area on the green form leaf than the variegated form. They showed the same preference at the beginning and the end of the experiment.
These results strongly indicate the little fitness difference between the variegated and green form. Although the variegated form grow green leaves in the different light environment, they are not for photoprotection. The ecological meaning of foliar variegation in Begonia formosana should be anti-herbivory, providing the prevention of visual herbivores to whole population.
| Identifer | oai:union.ndltd.org:TW/106NCHU5105067 |
| Date | January 2018 |
| Creators | Yi-Sian Lin, 林宜憲 |
| Contributors | 許秋容 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 62 |
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