| 摘要註: |
光照是影響蝴蝶蘭抽梗的重要環境因子之一，本論文將成熟的台灣阿嬤(Phalaenopsis aphrodite subsp. formosana)培養於生長箱，施予不同光照度處理六週，首先分別找出可以完全抑梗，及完全抽梗但不會造成光抑制的遮蔭與正常條件，然後比較在兩種條件下第二位葉的光合作用效率與生化代謝的差異；並將蘭苗移至催花生長箱，探討遮蔭對台灣阿嬤抽梗及開花品質，包括花梗數、花梗長、花朵數和第一朵花花徑的影響。論文第二部份則進一步比較於抽梗期間，即第二週至第四週，正常處理與遮蔭處理蘭株除了第二位葉的葉綠素a螢光效率、碳水化合物、有機酸及一些抗氧化相關的過氧化氫、維他命C、ascorbate peroxidase (EC 1.11.1.11)的差異外，並比較不同位葉在碳水化合物、有機酸、葉綠素與脂質相關代謝的差異，其中包括總脂質、脂質成份、脂質過氧化產物(malondialdehyde)及lipoxygenase (EC 1.13.11.12)活性，期望藉由上述差異的結果了解蝴蝶蘭苗的抽梗機制。實驗結果顯示，20 μmol m-2s-1以下，即每日的光積值在1.01 molm-2，可達100%抑梗(遮蔭處理)，而150 μmol m-2s-1可完全抽梗，並且無光抑制現象(正常處理)。遮蔭處理不僅降低蘭株的淨CO2吸收量與氧氣釋放量，亦減低phosphoenolpyruvate carboxylase﹙EC 4.1.1.31﹚、ribulose-1,5-bisphosphate carboxylase/oxygenase﹙EC 4.1.1.39﹚、NAD+- malic enzyme﹙EC 1.1.1.39﹚的活性及日韻律變化，造成葡萄糖、果糖、蔗糖與檸檬酸含量的減少，並且夜間蘋果酸累積量與白天澱粉堆積量亦受到影響。蝴蝶蘭葉片含有大量甘油，每克溼重將近有50毫克，此現象未曾被報導，而且甘油的含量不受遮蔭影響，其生理意義與代謝機制仍待進一步探討。遮蔭蘭株經過催花處理，雖然抽梗及開第一朵花的時間延遲約32至35天，但是開花品質並未受到影響。於抽梗過程，遮蔭與正常處理在葉綠素a螢光參數、總脂質、脂質成份、脂質過氧化產物及lipoxygenase活性的結果並未呈現顯著差異；相對的，在第二位葉的soluble ascorbate peroxidase活性、維他命C與葉綠素b含量，以及第一與第二位葉的蘋果酸、檸檬酸、澱粉及蔗糖含量，皆是正常處理顯著地高於遮蔭處理，其中尤其正常處理於第二週至第三週花梗萌出階段，蔗糖含量有明顯減少。因此，推測蔗糖含量的變化與蝴蝶蘭苗抽梗有密切關係。此外，第五位葉的葡萄糖與果糖含量遠高於第一與第二位葉，而且即使遮蔭處理仍維持相當量，暗示蝴蝶蘭不同位葉可能扮演不同的生理功能。 Light is one of the important environmental factors for spiking of Phalaenopsis. This thesis studied the mature Phalaenopsis aphrodite subsp. formosana plants cultured in growth chambers under different light conditions for six weeks. Firstly, to determine the light conditions that could completely inhibit spike emergence (shading condition) and induce spike emergence as well as no photoinhibition appearance (normal condition), separately. Then, the differences of the photosynthetic efficiency and biochemical metabolism of the second leaf between shading and normal conditions were compared. Finally, the plants of both treatments were transferred to the growth chamber for flowering, and the flowering qualities, such as flower stalk number, flower stalk length, floret number, and the diameter of the first floret were investigated. The second part of this thesis further studied the differences of chlorophyll a fluorescence, carbohydrates, organic acids, and some antioxidation-related analysis, such as H2O2, ascorbate and ascorbate peroxidase (EC 1.11.1.11) of the second leaf between shading and normal conditions during spike induction, namely, from the second to the fourth week. Moreover, the carbohydrates, organic acids, chlorophyll and lipid-related metabolisms, including total lipid, lipid composition, malondialdehyde (MDA) and lipoxygenase (EC 1.13.11.12) were compared between the various leaves. Results from the aforementioned analyses will conduce to understand the spiking mechanism of Phalaenopsis.The results clearly showed 20 μmolm-2s-1 irradiance, namely, 1.01 mole m-2 daily light integral and completely inhibited spike emergence (shading treatment), whereas 150 μmolm-2s-1 irradiance fully induced spiking and no photoinhibition exhibition (normal treatment). Shading not only decreased the rates of net CO2 uptake and O2 evolution, but also lowered the activities and diurnal rhythm of phosphoenolpyruvate carboxylase (EC 4.1.1.31), ribulose-1,5-bisphosphate carboxylase/oxygenase (EC 4.1.1.39), NAD+- malic enzyme (EC 1.1.1.39). Thus, the amounts of glucose, fructose, sucrose, and citrate were reduced. In addition, the amounts of nocturnal accumulated malate and daily deposited starch were also decreased. Unexpectedly, the leaf of Phalaenopsis was rich in glycerol, and reached to ca. 50 mg per g fresh weight. This phenomenon has never been reported, and its physiological significance and metabolic mechanism remain to be investigated. After the plants were transferred to the growth chamber for flowering, the flowering quality of the shaded plants was not affected, even though the spike induction day and flowering time of the first floret of the shaded plants was delayed ca. 32 to 35 days later than normal plants.During spike induction, the chlorophyll a fluorescence parameters, total lipid, lipid composition, MDA and lipoxygenase showed no significant differences between normal and shading treatments. By contrast, the soluble ascorbate peroxidase activity, ascorbate and chlorophyll b contents at the second leaf, and the malate, citrate, starch and sucrose levels at the first and the second leaves of normal treatment were consistently higher than those of shading treatment. In particular, the sucrose level at dawn was considerably decreased during spike emergence. Hence, it is speculated that there is a close relationship between a change of sucrose content and the spike emergence of Phalaenopsis. In addition, the glucose and fructose level at the fifth leaf was higher than that of the first and the second leaves, in spite of normal or shading treatment. This result strongly implies that the various leaves of Phalaenopsis perhaps play different physiological roles. |