碳氮對春石斛及蝴蝶蘭開花之影響

Abstract

蝴蝶蘭為臺灣重要之外銷花卉作物，而花形、色彩繽紛之春石斛被視為未來國際市場的新興花卉。植體碳氮比 (C/N ratio) 為植體中碳濃度和氮濃度的比例，高碳氮比被認為能促進生殖生長，低碳氮比被認為能促進營養生長甚至抑制開花，然植體碳氮比對於蘭花開花之影響研究鮮少。故本研究以春石斛 ( Dendrobium spp. ) 和蝴蝶蘭( Phalaenopsis spp. ) 為試驗材料，探討不同生育階段之碳氮養分變化，以及碳氮比對於蝴蝶蘭及春石斛開花之影響。 雜交春石斛 (Dendrobium Lai’s Yukisakura) 在生殖生長階段之植體碳濃度在花苞可見期有最小值46.2%，其他階段則無明顯變化 (47.1%-47.7%)。植體氮濃度在催花期間由1.03%下降至0.88%，在花苞可見期回升至1.13%。而春石斛植體碳氮比受氮濃度之影響，在催花期間由47.2上升至54.6，在花苞可見期下降至41.6。低溫催花期間，春石斛植體累積較多蔗糖和澱粉以供後續花序發育所需。 將春石斛易開花品種 (Den. Snow Princess × Den. Lucky Angel) 和不易開花品種 (Den. Oriental Smile × Den. Stardust ‘FireBird’) 依植株高度由高至低分為四個等級，並分析其葉片之碳氮濃度。易開花品種之葉片碳氮比較不易開花品種高，而不易開花品種之葉片碳氮比隨等級逐漸降低而有下降之趨勢。易開花品種之春石斛葉片碳氮比與腋芽可見日數之間沒有相關，然而在不易開花品種之春石斛葉片碳氮比與腋芽可見日數呈負相關 (r = - 0.64**)。兩品種葉片碳氮比與腋芽數和花朵數之關係皆呈正相關，葉片碳氮比越高，春石斛植體腋芽數和花朵數越多。試驗結果顯示春石斛葉片碳氮比可做為後續腋芽萌發數和花朵數之指標，低碳氮比導致其開花品質下降。 低溫催花前給予春石斛2個月的短期氮肥處理，氮肥濃度分別為0 ppm 、10 ppm、100 ppm和200 ppm。在施肥後到花朵開放期間，春石斛植體氮濃度隨施用氮肥濃度增加而上升。而植體碳氮比受氮濃度影響，隨施用氮肥濃度增加而下降。在200 ppm氮肥處理下，當代假球莖上萌發3.1個腋芽，為所有處理中最少 ，但腋芽乾重亦為所有處理中最重，為0.04 g。腋芽在後續可能會發育成為花苞或是高芽。在200 ppm氮肥處理下，春石斛有最少的花朵數但有最多的高芽數，分別為2.4朵和2.1個。在10 ppm氮肥處理下，春石斛開花節位比例最高，有3.1-3.4節，且花朵數有7.6朵，為各處理間最多。此外，相對於其他處理有較早開花之趨勢，顯示在低溫催花前給予春石斛2個月10 ppm的氮肥處理，能使其在後續花序發育有較佳的開花品質。 出瓶後2個月至7個月之紫色小花蝴蝶蘭 (Phalaenopsis Sogo Lotte ‘F2510’) 於人工氣候室經25/20℃涼溫催花後，出瓶後2個月之小苗抽梗率僅42%，顯示在此階段之小苗尚未完全脫離幼年性。在碳氮分析方面，出瓶後2個月之小苗第二片葉氮濃度為1.94%，且碳氮比為21.7，與出瓶後3個月至5個月之小苗相比，出瓶後2個月之小苗第二片葉氮濃度較高，且碳氮比較低。在開花方面，出瓶後2個月之小苗經低溫催花50 .2天後抽梗，抽梗天數在所有苗齡中最長；而出瓶後2個月之小苗花朵數僅4.6朵，為所有苗齡中最少。 白色大花蝴蝶蘭 (Phalaenopsis Sogo Yukidian ‘V3’) 植體碳氮比與抽梗日數、第一朵花苞可見日數、第一朵花開日數和90%花開日數沒有關係，然植體碳氮比和花序長度 (r = 0.40**)、花梗直徑(r = 0.36*)、第一朵花徑 (r = 0.45*) 和花朵數 (r = 0.41**) 呈正相關，顯示蝴蝶蘭植體碳氮比有做為開花品質指標之潛力。

Phalaenopsis is the major flower crop for export in Taiwan. Nobile-type dendrobium, which has various flower shapes and colors, is regarded as a potential flower crop for the international market. The ratio of C and N concentration in plant tissue is called C/N ratio. High C/N ratio is considered to promote reproductive growth and low C/N may boost vegetative growth or even inhibit flowering. However, literatures on how C/N ratio affects the flowering of orchids are limited. In this research, nobile-type dendrobium (Dendrobium spp.) and phalaenopsis (Phalaenopsis spp.) were used to investigate the changes in carbon (C) and nitrogen (N) of tissues during various development stages. The effect of carbon and nitrogen ratio (C/N) on flowering of nobile-type dendrobium and phalaenopsis was also studied. The hybrid dendrobium (Den. Lai’s Yukisakura) had the minimum C concentration of 46.2% at flower bud visible stage, but there was no significant difference of C concentration among other stages (47.1%-47.7%). The N concentration decreased from 1.03% to 0.88% during forcing then went up to 1.13% at flower bud visible stage. The C/N ratio, which was affected by the N concentration, increased from 47.2 to 54.6 during forcing and went down to 41.6 at flower bud visible stage. Nobile-type dendrobium mainly accumulated sucrose and starch during forcing for subsequent inflorescence development. The second experiment was to analysis leaf C and N concentrations of easy-flowering nobile-type dendrobium cultivars (Den. Snow Princess × Den. Lucky Angel) and not-easy-to-flower nobile-type dendrobium cultivars (Den. Oriental Smile × Den. Stardust ‘FireBird’). Based on the length of plant height, plants of each two nobile-type dendrobium cultivars was divided into four grades. Leaf C/N ratio of easy-flowering nobile-type dendrobium cultivars is higher than not-easy-to-flower nobile-type dendrobium cultivar. Leaf C/N ratio of not-easy-to-flower nobile-type dendrobium cultivar decreased as the grade decreased. No correlation between the leaf C/N ratio and days to axillary buds visible in easy-flowering nobile-type dendrobium cultivar was found. However, there was a negative correlation between the leaf C/N ratio and days to axillary buds visible (r = - 0.64**) in not-easy-to -flower nobile-type dendrobium cultivar. In addition, there was a positive correlation of the C/N ratio with number of axillary buds and number of flowers in both cultivars. The higher leaf C/N ratio, the greater number of axillary buds and flowers existed in the plant. These results indicate that the leaf C/N ratio can be used as an indicator for the number of axillary buds and the number of flowers in nobile-type dendrobium, and low leaf C/N ratio may lead to the decrease in flower quality. The third experiment was giving nobile-type dendrobium two months of short-term nitrogen fertilizer treatment before forcing, with nitrogen fertilizer concentration of 0, 10, 100, or 200 ppm. From the start of fertilization to the time of flower opening, N concentration of plants increased as nitrogen fertilizer concentration increased. The C/N ratio, which was affected by the N concentration, decreased as nitrogen fertilizer concentration increased. The dendrobium which were treated with 200 ppm nitrogen fertilizer had the lowest number but the heaviest dry weight of axillary buds, which were 3.1 and 0.04 g, respectively. Axillary buds may later develop into flower buds or keikis. Besides, nobile-type dendrobium had the least number of flowers (2.4) but the most number of keikis (2.1) after treated with 200 ppm nitrogen fertilizer. Nobile-type dendrobium under 10 ppm nitrogen treatment had the most number of node bearing inflorescence (3.1-3.4) and flowers (7.6), and flowered earlier than other treatments. To sum up, giving nobile-type dendrobium two months of 10 ppm nitrogen fertilizer treatment before forcing can make better flowering quality of nobile-type dendrobium. Small, purple-flowerd phalaenopsis (Phal. Sogo Lotte ‘F2510’) with different plant maturity were placed in phytotron at controlled day/night temperature of 25/20℃ for cool-temperature forcing. The flower-stalk emergence rate of 2 months after deflasking plants was only 42%, which indicates that the plants were not completely out of the juvenile phase. Two months after deflasking, plants had higher N concentration (1.94%), lower C/N ratio (21.7), the longest days to spiking (50.2), and minimum number of flowers (4.6) compared with plants deflasked for 3 to 5 months. No correlation of the C/N ratio with days to spiking, days to first visible bud, days to first flower open and days to 90% flower open in large, white-flowered phalaenopsis (Phal. Sogo Yukidian ‘V3’) was discovered. However, there was a positive correlation between the C/N ratio and inflorescence length (r = 0.40**), flower-stalk diameter (r = 0.36*), first flower diameter (r = 0.45*) and number of flowers (r = 0.41**). Thus, the C/N ratio has the potential for becoming flowering quality index in phalaenopsis.