不同簇生敏感度及開花時間洋桔梗品種之相關研究

洋桔梗[Eustoma exaltatum subsp. russellianum (Hook.)]因花型、花色多樣、且瓶插壽命長，為世界重要之切花，亦為臺灣產量及種植面積排名前十的切花作物；然而臺灣於夏季生產洋桔梗種苗易因高溫導致簇生化發生，使穴盤苗品質降低，而簇生化相關之形態生理研究較少，故本研究利用數種耐熱指標探討不同簇生敏感度洋桔梗於高溫下的形態、生理及光合作用表現。而高溫長日下常使洋桔梗未達切花標準，故於夏季生產時常使用晚生品種，但早中晚生洋桔梗特性會受溫度影響，可能與其影響葉片分化及細胞膜通透性有關。故本研究探討早中晚生洋桔梗於不同溫度下之開花時間與細胞膜穩定性之關係。使用子葉展開之不同簇生敏感度洋桔梗品種，於日/夜溫25/20及30/25°C處理至第三對葉完全展開時，調查其形態及生理差異，並於後續調查其簇生百分比。結果顯示30/25°C處理參試品種依簇生敏感度由低至高依序為‘Mazurka White’ (6.1%)、‘Mazurka Blue Picotee B’ (7.6%)、‘Tainan No. 3’ (21.3%)、‘Tainan No. 4’ (23.3%)、‘Soiree Pink Picotee’ (60.2%)、‘Diamond Peach’ (98.6%)。簇生敏感度高如‘Soiree Pink Picotee’及‘Diamond Peach’於30/25°C下有較厚、寬的葉片、SPAD-502讀值較高且其保衛細胞較大，具有低的葉片相對傷害值(relative injury; RI)及較大的乾重。然而葉綠素螢光及根部活性與簇生敏感度無相關性。‘Soiree Pink Picotee’及‘Diamond Peach’於30/25°C下之簇生株較25/20°C抽苔株有較高的氣孔導度、蒸散速率及淨光合作用；‘Mazurka White’、‘Mazurka Blue Picotee B’、‘Tainan No. 3’、‘Tainan No. 4’ 於30/25°C下之抽苔株較25/20°C抽苔株有較低的氣孔導度、蒸散速率及淨光合作用。將不同簇生敏感度洋桔梗品種於形成可見花芽時移至15/13、20/15、25/20、30/25及35/30°C處理，開花時取花粉以二乙酸螢光素酯(fluorescein diacetate; FDA)染色評估活性，簇生敏感度低的‘Mazurka White’、‘Mazurka Blue Picotee B’、‘Tainan No. 3’、‘Tainan No. 4’於25/20至35/30°C有較高的花粉活力；而簇生敏感度高的‘Soiree Pink Picotee’、‘Diamond Peach’其花粉活力於25/20°C即開始下降。在25/20及35/30°C下，所有品種花粉皆可於雌蕊中萌發並於3天內完成受精。將不同簇生敏感度洋桔梗品種種子播種於8.3-38.3°C，調查其每日發芽率，並計算三基點溫度及溫度積值。結果顯示所有參試品種的發芽三基點溫度皆相似，無法作為簇生敏感度之指標。基礎溫度(minimum temperature; Tmin)為9.6-9.8°C；最適溫度(optimum temperature; Topt)為30.2-31.5°C；最高溫度(maximum temperature; Tmax)為38.0-38.6°C。而發芽至50%所需溫度積值(thermal time; θ50)介於76.4-110.3°Cd，雖然品種間有差異，但與其簇生敏感度無相關性。將帶有2對本葉之不同早中晚生洋桔梗於15/13、25/20及35/30°C下生長，調查苗期RI值、開花時間及株高等性狀。結果顯示早生(‘Soiree Pink Picotee’及‘Soiree Pink Blush’)及中生(‘Tainan No. 3’及‘Tainan No. 4’)品種於各溫度處理1-5週的RI值皆無明顯變化；晚生品種(‘Rosita IV Purple’及‘Arena IV Rose’)於25/20及35/30°C處理下1-5週亦無明顯變化，但於15/13°C處理下，兩品種的葉片RI值增加。早中晚生品種於35/30°C下花下節位數、達可見花芽及花藥開裂天數、株高差異較小；但隨著溫度降低至25/20及15/13°C，品種間的差異增加，以晚生品種有較大的花下節位數、到花天數及株高。早中晚生洋桔梗品種於15/13°C處理5週之葉片RI值與達可見花芽延遲天數呈現二次曲線正相關。將早中晚生洋桔梗品種種子播種於8.9-38.0°C。結果顯示品種之間的發芽三基點溫度皆相似，無法作為區別早中晚生之指標。Tmin為8.7-9.4°C；Topt為28.4-28.7°C；Tmax為37.4-38.3°C。而θ50介於88.2-102.7°Cd，品種間差異小，亦無法作為區別早中晚生之指標。

關鍵字

電解質滲漏；光合作用；花粉活力；種子發芽

並列摘要

Lisianthus [Eustoma exaltatum subsp. russellianum (Hook.)] is an important cut flower in the world due to its diverse flower patterns, colors, and long vase life. Lisianthus ranks the top ten cut flower crops in Taiwan in terms of yield and planting area. However, plug production of Eustoma in Taiwan is prone to rosette due to high temperature in summer. Morphological and physiological studies to Eustoma cultivars with different rosette sensitivity at presently limited. In addition, Eustoma plants often fail to produce standard and long cut flowers under high temperature and long-day conditions. Therefore, late-flowering cultivars are often used during summer production in Taiwan. However, flowering time in Eustoma cultivars may differ according to cultivation temperature, which may affect leaf initiation via cell membrane stability. Therefore, this study investigated the relationship between temperature and flowering time and cell membrane thermostability of Eustoma cultivars with different flowering time. Seed of six of Eustoma cultivars with different rosette sensitivity were sown and seedlings were grown at 25/20 and 30/25°C. Morphological and physiological measurements were taken when seedlings had the three unfolded leaf pairs, and subsequent rosette percentage was investigated. Cultivars were ranked according to rosette sensitivity at 30/25°C treatment from low to high as: ‘Mazurka White’ (6.1%), ‘Mazurka Blue Picotee B’ (7.6%), ‘Tainan No. 3’ (21.3%), ‘Tainan No. 4’ (23.3%), ‘Soiree Pink Picotee’ (60.2%), and ‘Diamond Peach’ (98.6%). Cultivars with higher rosette sensitivity such as ‘Soiree Pink Picotee’ and ‘Diamond Peach’ had thicker, wider leaves, higher SPAD-502 value, and larger guard cell irrespective of temperature, and had lower leaf relative injury (RI) and higher dry weights at 30/25°C. Chlorophyll fluorescence and root activity were not correlated with rosette sensitivity. The rosette plants of ‘Soiree Pink Picotee’ and ‘Diamond Peach’ at 30/25°C had higher stomatal conductance, transpiration rate and net photosynthesis than bolting plants at 25/20°C. ‘Mazurka White’, ‘Mazurka Blue Picotee B’, ‘Tainan No. 3’, ‘Tainan No. 4’ had lower stomatal conductance, transpiration rate and net photosynthesis at 30/25°C than at 25/20°C. Eustoma cultivars with different rosette sensitivity were transferred at visible bud stage to 15/13, 20/15, 25/20, 30/25, and 35/30°C to test pollen viability and in vivo pollen germination. Result show that ‘Mazurka White’, ‘Mazurka Blue Picotee B’, ‘Tainan No. 3’, and ‘Tainan No. 4’ with lower rosette sensitivity had higher pollen viability at 25/20°C to 35/30°C, while ‘Soiree Pink Picotee’, and ‘Diamond Peach’, with higher rosette sensitivity, pollen viability were reduce at 25/20°C. In vivo observation showed that pollen of all cultivars germinated and fertilization took place within 72 h at both 25/20 and 35/30°C. Seeds of Eustoma cultivars with different rosette sensitivity were sown at 8.3-38.3°C to measure their daily germination. Results showed that cardinal temperatures of germination was similar among cultivars, and did not correlate to rosette sensitivity. Minimum (Tmin), optimum (Topt), and maximum (Tmax) temperature for germination in Eustoma is estimated to be 9.6-9.8, 30.2-31.5, and 38.0-38.6°C, respectively. Thermal time required to reach 50% germination (θ50) is between 76.4-110.3°Cd. Although θ50 were different among cultivars, there was no correlation with their rosette sensitivity. Seedlings of Eustoma, with different flowering time, were grown at 15/13, 25/20 and 35/30°C. The leaf RI value of early-flowering (‘Soiree Pink Picotee’ and ‘Soiree Pink Blush’) and middle- flowering (‘Tainan No. 3’ and ‘Tainan No. 4’) did not change significantly during 5 weeks of temperature treatments. The leaf RI value of late-flowering cultivars (‘Rosita IV Purple’ and ‘Arena IV Rose’) did not change significantly at 25/20 and 35/30°C, but increased at 15/13°C. Node number below flower, days to flowering, and plant height of Eustoma cultivars with different flowering time were only slightly different at 35/30°C, the differences between cultivars increased when the temperature decreased to 25/20 and 15/13°C. The late-flowering cultivars had larger number of nodes, days to flowering and plant height. The leaf RI value of Eustoma cultivars with different flowering time at 5 weeks after 15/13°C treatment showed a quadratic positive correlation, with the delay in time to visible flower buds at 15/13°C when compared to 25/20 or 35/30°C. Seeds of Eustoma cultivars with different flowering time were sown at 8.9-38.0°C and daily germination was recorded. Results showed that the cardinal temperatures of germination were similar among the cultivars, and did not correlate with flowering time habits. Tmin, Topt and Tmax were 8.7-9.4, 28.4-28.7, and 37.4-38.3°C, respectively. θ50 was not significantly different between cultivars and ranged between 88.2-102.7°Cd, and did not correlate with flowering time habits.