春石斛光合作用、 開花調節及貯運技術之研究

Abstract

近年來，臺灣春石斛(Dendrobium spp.)產量持續上升，是很有潛力之盆花作物。然目前商業栽培之技術，尚待更進一步改善及提升。為提高盆花品質，首先要瞭解各種環境因子對春石斛的生理之影響。本研究主要分為三個主題，包括探討春石斛的光合作用型式和季節性變化、開花調節、及長時間黑暗貯運對春石斛之影響。 為瞭解春石斛之光合作用型式，本研究使用春石斛D. Lan Tarn Beauty, D. Lucky Girl 及 D. Second Love 'Tokimeki'為材料，測定其根部、假球莖及葉片之δ13C。結果顯示，三品系各器官的δ13C值介於-23.9‰ 到 -26.0‰間。另外，測定植株光合作用日變化，結果顯示三品系之日間淨光合作用速率(Pn)為正值，而夜間則趨近於零。綜合上述，春石斛屬C3植物。另外，測量春石斛之光反應曲線，結果指出三品系春石斛在2010年9月9日和11月21日之光飽和點為245至275 μmol•m-2•s-1 photosynthetic photon flux density (PPFD)。更進一步探討四季變化對春石斛光合作用之影響，結果顯示植株在春、秋兩季有較高的Pn，而在冬天光合作用會受到抑制。夏天時，當葉溫達36.4 oC，植株之光合作用到受抑制。因此在春石斛栽培時，若溫度在18-30 oC內，建議將光度維持在500-600 μmol•m-2•s-1 PPFD，而當溫度超過此範圍，則將光度調降至300-400 μmol•m-2•s-1 PPFD。 為瞭解溫度對春石斛開花之影響，本研究在春化作用時及春化作用後給予不同溫度處理。結果顯示D. Lucky Girl則需每日16小時15/13 oC的低溫處理4週才能滿足其低溫需求。若於為期4週之春化處理期間 (15/13 oC)，以25/20 oC在第 2或第3週進行熱中斷處理，在第3週進行熱中斷能延遲D. Lan Tarn Beauty和D. Lucky Girl的開花而不影響植株之櫥架壽命。在春石斛花苞發育期給予不同溫度處理，結果顯示20/15 oC之處理花色較深；而置於30/25 oC之植株最早開花，D. Lan Tarn Beauty與D. Lucky Girl的到花天數分別為28和32天；相較於30/25 oC，置於25/20 oC者之到花時間延後6-7天，然花徑較大。而在35/30 oC下，植株雖可開花但會產生畸形花。 在採後處理方面，本研究探討貯運溫度（10、15、20及 25 oC）和時間（7、14及21天）對D. Lan Tarn Beauty與D. Lucky Girl貯後光合作用與後續開花品質之影響。經黑暗貯運後，兩品系植株之Pn皆接近零，然隨貯後時間增加可逐漸恢復。貯運溫度和時間增加會導致貯後光合作用的恢復期延長。D. Lan Tarn Beauty經10 oC 黑暗貯運貯運21天後，Pn需要4天恢復。當貯運溫度從15 oC提高至25 oC會使Pn之恢復期由8天增加至12天；另外，當貯運時間由 7天延長至21天 (貯運溫度15 oC)，會導致植株之Pn恢復期由1天延長至12天。貯後植株經催花後，貯運於10 oC者較其他組別提早開花。而貯運於20 oC 或 25 oC會導致植株觀賞期縮短。綜合上述，可得春石斛長時間黑暗貯運之適貯溫度為10 到 15 oC之間。

With the increasing popularity, nobile Dendrobium is a promising potted flower commodity in the near future. Physiological studies of nobile Dendrobium is required to understand the conditions that can yield the best potted flower product. This study was characterized to three major topics, including patterns and seasonal changes of photosynthesis, methods of flowering regulation, and effects of long-term dark shipping effect on nobile Dendrobium. Dendrobium Lan Tarn Beauty, D. Lucky Girl, and D. Second Love 'Tokimeki' were used for determining their photosynthesis pattern. The result of the δ13C values in the plant organs (roots, pseudobulb, and leaves) ranged from -23.9‰ to -26.0‰ among three cultivars. In addition, net CO2 uptake rates (Pn) in the three cultivars were positive during daytime and were nearly zero at night based on diurnal observations. Combination of both results suggested strongly that nobile Dendrobium is a C3 plant. Light response curve of all three cultivars showed the light saturation points (measured in 9 Sept. and 21 Nov. 2010) ranged from 245 to 275 μmol•m-2•s-1 photosynthetic photon flux density (PPFD). Under high-light environment, autumn and spring were the seasons where nobile Dendrobium showed highest photosynthesis capacity, and photosynthetic limitation occurred during winter. In the summer, photosynthetic depression occurred when the leaf temperature elevated to 36.4 oC. Therefore, a light intensity up to 600 μmol•m-2•s-1 PPFD is recommended for nobile Dendrobium production at 18 to 30 oC, but for D. Lucky Girl and D. Second Love 'Tokimeki', the light should be reduced to 400 - 500 μmol•m-2•s-1 PPFD when the temperature is not controlled. Temperature controls during or after vernalization were used to manipulate the flowering of D. Lan Tarn Beauty and D. Lucky Girl. Vernalization chilling requirement of D. Lucky Girl required at least 16 h daily chilling (15/13 oC) for 4 weeks. In the effort of delaying flowering time, heat interruption at 25/20 oC applied on the third week under a scheme four weeks could delay flowering of D. Lan Tarn Beauty and D. Lucky Girl for 14 and 16 days, respectively, without reducing the shelf-life. During flower bud development, plants kept at 20/15 oC had stronger flower coloration; those kept at 30/25 oC developed the quickest to flower in both cultivars. Plants in temperature regimen of to 25/20 oC resulted in 6 to 7 days late to flower but with larger flower diameter comparing with those of 30/25 oC. Plants could flower at 35/30 oC but with malformations. Various temperatures (10, 15, 20 and 25 oC) and durations (7, 14, 21 days) of simulated dark shipping (SDS) were applied for D. Lan Tarn Beauty and D. Lucky Girl. After SDS, Pn of both cultivars decreased to nearly zero but could gradually recover thereafter. Recovery time was delayed with increasing temperature and duration of SDS. Dendrobium Lan Tarn Beauty stored at 10 oC for 21 days had the shortest time (4 days) to recover to normal photosynthetic status and the recovery time prolonged to 8 to 12 days with increasing the SDS temperatures from 15 oC to 25 oC. In addition, photosynthetic recovery time prolonged from 1 to 12 d with increasing storage duration from 7 to 21 d when stored in 15 oC. After flower forcing, plants stored at 10 oC flowered earlier than other treatments. Shorter shelf-lifes were found in D. Lan Tarn Beauty stored at 20 and 25 oC than unshipped plants. As a result, nobile Dendrobium could be stored at 10 to 15 oC for prolonged SDS to 21 d.