植物生長調節劑對檸檬綠文心蘭開花之影響

文心蘭Oncidesa Gower Ramsey ‘Honey Angel’為臺灣最重要的切花作物。商業生產上有少數業者會使用細胞分裂素 (6-benzyladenine, 6-BA) 及赤黴酸 (gibberellic acid, GA3)，分別預期達到增加側芽數及增加花序長度之效果。但目前這兩種藥劑的施用效果並不明確，因此運用不廣泛。並且在側芽及花芽生長的不同階段，植株對6-BA及GA3的效果應有所差異，因此本研究以切片觀察‘Honey Angel’芽體發育情況，再測試植物生長調節劑於不同時機施用之效果。文心蘭會膨大形成假球莖，假球莖基部之節位為第0節，節位數第0節的芽體通常會發育為花芽，而更低節位之芽體則發育為營養芽。將不同長度當代莖之側芽取下以切片觀察，當代莖長10 cm時花芽尚未萌動。在當代莖生長初期，下方營養芽的長度及節位數均大於花芽，然而在後期當代莖長25 cm至30 cm時 (30 cm為當代莖假球莖出鞘期)，較近基部的營養芽的節位數及長度上升趨緩，而花芽的節位數及長度則快速上升至與營養芽相同，並且分化出花序側分枝的構造。綜合以上，當代莖長10 cm時，花芽尚未萌動，而當代莖25 cm至30 cm，假球莖出鞘期為花芽分化之關鍵時期。取當代莖長10 cm之植株噴施0、100、200、300、400、500或600 mg·L-1 6-BA，各處理間下一代芽數並無顯著差異。依據先前試驗，當代莖長10 cm時，營養芽長度約5 mm，推測是因為芽體成熟度不足，造成6-BA之效果不顯著。後續試驗於當代莖長度15 cm、20 cm或25 cm時施用300或600 mg·L-1 6-BA。結果顯示相較於對照組，25 cm當代莖施用300 mg·L-1 6-BA使營養芽數由1.1上升為1.6個。當代莖長25 cm為營養芽發育較成熟之階段，因此推測營養芽成熟度會影響6-BA促進側芽萌發之效果。取具40至60 cm之花梗之植株，全株噴施0、12.5、25、50或100 mg∙L-1 GA3。100 mg∙L-1 GA3使小花數與花苞數下降，50或100 mg∙L-1 GA3相較於對照組採收天數提前7至9天。12.5 mg∙L-1 GA3造成黃葉率上升，且黃葉率隨著濃度上升而增加。取具10至30 cm花梗之植株處理25至200 mg∙L-1 GA3，小花及花苞數施用GA3後略微下降，但無顯著差異。GA3使第一朵小花開放時間提前，50、150與200 mg∙L-1 GA3處理採收天數提前9天。但150及200 mg∙L-1 GA3會使小花唇瓣出現較嚴重的畸形。兩次試驗結果顯示，施用GA3無法使花序長度增加，但可使採收時間提前。總結以上結果，文心蘭花芽分化之關鍵期介於當代莖長25至30 cm，植株假球莖明顯膨大至出鞘的時期。於當代芽長25 cm時施用6-BA能夠增加營養芽萌發數目，顯示較成熟的文心蘭營養芽施用6-BA後有較高的機會抽出。文心蘭花序施用GA3可使花序採收提前7至9天，但會導致植株黃葉、小花數下降或花序畸形。

關鍵字

文心蘭；花芽及營養芽發育；細胞分裂素；赤黴酸

並列摘要

Oncidesa Gower Ramsey ‘Honey Angel’ is the most important cut flower for export in Taiwan. Some Oncidesa growers use 6-benzyladenine (6-BA) and gibberellic acid (GA3) to promote vegetative bud emergence and to increase the length of inflorescences, respectively. However, the effectiveness of 6-BA and GA3 is not comfirmed, so these plant growth regulators are not widely used yet. Growth responses of axillary buds to 6-BA and GA3 may be different when treated with 6-BA or GA3 at various development stages. Here, we report our studies on growth of vegetative and flower buds in ‘Honey Angel’, and evaluate the effects of 6-BA and GA3 on various growth stages. A part of Oncidesa stem enlarges to form a pseudobulb, the base of pseudobulb was referred to as 0th node. A flower stalk usually developes from the 0th node. Vegetative buds usually emerge from the lower nodes. Axillary buds on a developing shoot were detached from current shoots at various lengths for observating following sectioning. The observed flowering stem length and node number suggest that flower buds had not activated when current shoot was 10 cm. In the early stage of the current shoot growth, vegetative buds were bigger and had a greater number of nodes than flower buds. However, there was no further growth in number of nodes and length in vegetative buds on lower nodes when current length was 25 cm to 30 cm (a 30 cm shoot was at unsheathing stage). Meanwhile, number of nodes and length of flower buds became the same with the vegetative buds, and the branch prinordia started to dfferentiate. In summary, when current shoots were 10 cm, flower buds had not activated. Current shoots length 25 to 30 cm was the critical stage for flower bud differentiation. The primordia of branches on a flower stalk formed when the current shoot was 25 cm to 30 cm. Current shoots at 10 cm were used for 6-BA treatments, the results showed that treatment with 0, 100, 200, 300, 400, 500, or 600 mg·L-1 6-BA did not increase the number of emerged vegetative buds. According to previous experiment, vegetative buds were 5 mm when current shoot was 10 cm long. The failure of promoting vegetative bud emergence might be caused by immaturity of vegetative buds. In the following experiment, plants were sprayed with 300 or 600 mg·L-1 6-BA when current shoot was 15, 20, or 25 cm. Treatment of 300 mg·L-1 6-BA increased number of emerged vegetative buds on the 25 cm current shoots from 1.1 to 1.6. Current shoot at 25 cm was the stage when vegetative buds became more mature. Results showed that the maturity of vegetative buds influenced the effect of 6-BA treatments. Oncidesa plants with 40 to 60 cm inflorescences were treated with GA3 at concentrations of 0, 12.5, 25, 50, or 100 mg∙L-1. Treatment of 100 mg∙L-1 GA3 reduced the number of florets and buds. Plants treated with 50 and 100 mg∙L-1 GA3 reduced days to harvest by 7 to 9 days. Concentrations above 12.5 mg∙L-1 increased leaf yellowing. As the concentration raised, leaf chlorosis was more severe. In another experiment, plants with 10 to 30 cm inflorescences were used and GA3 was applied. GA3 slightly reduced the number of florets and buds, but without statistical difference. All GA3 treatments hastened the first floret anthesis, and 50, 150, or 200 mg∙L-1 GA3 reduced days to harvest by 9 days. Treatments of 150 mg∙L-1 and 200 mg∙L-1 GA3 caused serious floret malfunction on labellum. The results indicate that GA3 application did not elongate inflorescence, but shortened time for harvest. In conclusion, the differentiation of flower stalk occurred when current shoot length was 25 cm to 30 cm, when the pseudobulb started to swell and unsheathe. 6-BA promoted vegetative buds to emerge when applied on 25 cm long current shoots. These results suggested that larger and more mature vegetative buds were more likely to emerge when stimulated by 6-BA. Application of GA3 reduced days to harvest by 7 to 9 days. Nevertheless, GA3 increased rate of leaf chlorosis and malfunction inflorescences; furthermore, GA3 decreased floret number of Oncidesa.