文心蘭‘檸檬綠’碳水化合物與開花能力之相關性

Abstract

本研究探討文心蘭植體碳水化合物與其開花之相關性。首先調查文心蘭在不同的生育階段中碳水化合物之代謝及利用。包含花序發育過程對假球莖中碳水化合物之利用、營養芽發育時對前代假球莖中碳水化合物之使用、營養芽間養分之競爭，以及花序採收後切花內碳水化合物之分配。接著探討碳水化合物與開花能力之相關性，以不同株齡之文心蘭比較碳水化合物變化，以及分析正常栽培下未開花與開花之成熟株間碳水化合物之差異。 文心蘭發育過程碳水化合物的代謝與利用方面，第一個試驗調查花序發育過程當代假球莖與花序內碳水化合物之消長。以花序發育至10、35、65公分、側分枝發育完成、50%花朵開放，五個階段進行取樣分析。當代假球莖在花序發育初期含有大量的葡萄糖及果糖，隨著花序發育將其利用而下降。花序內則逐漸累積可溶性醣、澱粉以及甘露聚醣。在花苞開放時，花苞內蔗糖、甘露聚醣之濃度下降，葡萄糖及果糖則快速累積，推測是以單醣調節水勢促進花朵展開之機制。第二個試驗調查當代莖發育過程中，對於前代假球莖內碳水化合物之利用。將文心蘭栽培兩個生長週期，並定期取樣進行碳水化合物分析。且由於多個當代莖同時發育可能會彼此競爭碳水化合物，故此試驗中使用具有一個或兩個新芽之植株進行比較。具有一個新芽之植株在發育時會消耗前一代莖內的澱粉，而具兩新芽之植株會同時消耗前一代及前二代莖內之澱粉。具有兩個新芽的植株，在兩個生長週期中發育之假球莖體積皆小於僅具有一個新芽之植株，並且累積較少的可溶性醣，可能會降低後續花序之品質。 在碳水化合物與開花能力相關性的部分，調查出瓶0.0、0.5、1.0、1.5及2.0年之文心蘭植株，試驗植株在出瓶1.5年以前不具開花能力，而2.0年之植株則已開過花。文心蘭的第一個假球莖於出瓶後0.5年形成，假球莖成熟後植株沒有開花，並由基部萌發下一個世代之營養芽，隨著株齡增加前代莖的數量也隨之增加。當代假球莖中單醣濃度從0.5至1.5年逐漸上升，直到出瓶2.0年，植株開花後濃度下降。推測隨著單醣濃度提高，文心蘭才能提供足夠花序發育之碳水化合物。前代莖中則以澱粉為碳水化合物儲存之形式，其濃度亦隨著株齡上升，儲存澱粉的總量也由於前代假球莖數量增加有顯著的上升，推測澱粉與文心蘭的熟度與開花能力相關，也推測當代假球莖中單醣濃度之上升是因為在發育過程中有更多的澱粉由前代假球莖供給。另一方面在一般栽培環境下的未開花的文心蘭成熟株中，前一代假球莖的澱粉含量遠低於正常開花株，也印證了前代假球莖中是否有充足的澱粉供應對文心蘭的開花能力有顯著的影響。 文心蘭的前代假球莖儲存大量之澱粉，其澱粉隨著植株成熟度增加，並且影響植株的開花能力。當代假球莖發育時累積大量的單醣，並在當代假球莖成熟後隨著花序發育逐漸下降。新芽數量增加會消耗更多前代假球莖中儲存之澱粉，亦會造成當代假球莖體積下降以及其中的可溶性醣含量下降。本研究顯示當代莖是提供花序發育養分的重要部位。但是除了當代莖以外，前代莖為文心蘭重要之養分儲存器官，並影響文心蘭的發育與開花。在文心蘭的栽培管理上，使前代莖能持續地累積碳水化合物對植株整體之生長品質十分重要。

This study explored the relationship between carbohydrate and flowering in Oncidesa. First, carbohydrate metabolism and utilization during various growth stages were examined, including the use of carbohydrates in the current pseudobulb during inflorescence development, the use of carbohydrates stored in back pseudobulbs by vegetative shoot growth, the competition of carbohydrates between vegetative shoots, and the carbohydrate partitioning in the inflorescence after harvest. Furthermore, the relationship between carbohydrate and flowering ability was investigated. We used Oncidesa plants of various ages to analyze the carbohydrate changes along the maturity increase. The carbohydrates in the non-flowering mature plants grown under regular cultivated conditions were also analyzed. First, the metabolism and utilization of carbohydrates during Oncidesa growth were examined. In experiment I, The plants were sampled at five stages, with the inflorescence developed to 10 cm, 35 cm, 65 cm, branches well developed, and 50% florets opened, to investigate the carbohydrate changes during inflorescence development. The current pseudobulb initially contained a large amount of glucose and fructose, and then the sugars decreased for the inflorescence development. The soluble sugars, starch, and mannan accumulated in the developing inflorescence. When the floret bud opened, the concentrations of sucrose and mannan decreased, and the glucose and fructose rapidly rose in the floret bud, which might be the bud opening mechanism controlled by sugar-regulated water potential. In experiment II, the utilization of carbohydrates stored in the back pseudobulbs during current shoot growth was investigated. The Oncidesa plants were grown for two growth cycles and sampled regularly. The plants with one or two new shoots were used because multiple current shoots might compete for the starch stored in the back pseudobulbs. The plants with one new shoot consumed the starch in the first back pseudobulb as it developed, while the plants with two new shoots consumed starch in the first and second back pseudobulbs simultaneously. The pseudobulbs formed by plants with two new shoots during the two growth cycles were smaller than those with only one new shoot. Furthermore, the soluble sugar content in the current pseudobulb was lower, which might reduce the quality of cut flowers. The Oncidesa at 0.0, 0.5, 1.0, 1.5, and 2.0 years after deflasking were used to investigate the relationship between flowering ability and carbohydrate. The plants younger than 1.5 years after deflasking did not possess the flowering ability, and the plants at 2.0 years had already flowered. The first pseudobulb of the Oncidesa developed at 0.5 year. The inflorescence did not develop, and the next vegetative shoot emerged from the base of the shoot after the first pseudobulb matured. The number of the back shoots increased as plant age increased. The monosaccharide concentrations in the current pseudobulb increased from 0.5 to 1.5 years and decreased after flowering at 2.0 years. As the monosaccharide concentration elevated, the Oncidesa might have enough carbohydrate for inflorescence development. In the back pseudobulbs, the major carbohydrate reserve form was starch. The starch concentration increased along with the time after deflasking, and the total amount of starch increased significantly with the increasing number of back pseudobulbs, which suggests that starch correlates the plant maturity and flowering ability in Oncidesa. The increasing monosaccharides in the current pseudobulb might be contributed by the significantly increasing starch amount in the back pseudobulbs. On the other hand, the starch in the back pseudobulb of the non-flowering mature plants grown under a regular cultivation environment was significantly less than that in flowering plants which showed that the starch in the back pseudobulb had a significant influence on flowering ability. The back pseudobulbs of Oncidesa store a large amount of starch. The starch increases as the maturity of the Oncidesa plant increases, which affects the flowering of plants. The current pseudobulb accumulates monosaccharides during development. After the current pseudobulb matures, the monosaccharide content gradually decreases with the development of inflorescences. The increase in the number of new shoots consumes more starch accumulated in the back pseudobulbs, which causes a smaller current pseudobulb and less soluble sugar in the current pseudobulb. This study shows that the current shoot is an important part of providing carbohydrates for inflorescence development. However, in addition to the current shoot, the back shoots are also important nutrient storage organs and affect the development and flowering of Oncdiesa. In the cultivation and management of Oncidesa, sufficient photosynthesis and carbohydrate accumulation in the back shoots is important for the overall growth quality of the Oncidesa.