於密閉型植物工場水耕栽培萵苣(Lactuca sativa L.)苗菜

植物工場為一可控制環境之栽培結構，於植物工場內可以水耕方式全年生產無農藥、低生菌數、低硝酸鹽含量及高產量之鮮食蔬菜。萵苣苗菜具有生長期短、可生食及輕加工利用等優點，適於植物工場經濟栽培。本研究以‘Gentilina White’、‘Island Cos’、‘Lollo White’及‘Red Salad Bowl Improved’萵苣苗菜為試驗材料，探討適合於植物工場水耕栽培萵苣苗菜之養液配方及環境條件。在日/夜溫25 ℃/20 ℃生長箱中，採用白光發光二極體(light-emitting diode, LED)，光量為200 μmol･m-2･s-1，每日照光16 h，以每穴單株疏植、栽培密度464 plant･m-2，測試Hoagland配方養液之最適電導度，在0.3、0.5、0.7、0.9、1.0、1.1與1.2 dS･m-1共七種電導度中，‘Gentilina White’及‘Island Cos’最適用1.0 dS･m-1，‘Lollo White’及‘Red Salad Bowl Improved’最適用1.1 dS･m-1。復於上述條件之生長箱中，使用Hoagland配方養液測試栽培密度，包括每穴單株疏植之栽培密度464 plant･m-2、每穴單株密植929 plant･m-2、每穴雙株疏植929 plant･m-2與每穴雙株密植1858 plant･m-2，結果以每穴單株疏植464 plant･m-2之單株鮮重最大，‘Gentilina White’、‘Island Cos’、‘Lollo White’及‘Red Salad Bowl Improved’分別為1.8、2.4、3.0及3.1 g･plant-1。繼於25℃密閉型植物工場，利用Hoagland養液，每穴單株疏植464 plant･m-2，以光量236、200與164 μmol･m-2･s-1之T5螢光燈每日照光16 h，其中於236 μmol･m-2･s-1栽培之單株鮮重最大，‘Gentilina White’、‘Island Cos’、‘Lollo White’及‘Red Salad Bowl Improved’分別為3.0、2.4、1.8及1.4 g･plant-1，葉數、葉長與葉綠素計讀值亦最大，且葉片硝酸鹽含量較低，分別為413、435、2157與2348 ppm。再於密閉型植物工場以236 μmol･m-2･s-1之T5燈每日照光16 h，在日夜溫25 ℃/20℃、25 ℃/15 ℃及20 ℃/20 ℃下栽培，20 ℃/20 ℃之單株鮮重最低，而‘Gentilina White’與‘Red Salad Bowl Improved’於25 ℃/15 ℃之葉片可溶性固形物比25 ℃/20 ℃者高。復於25 ℃/20 ℃密閉型植物工場，使用236 μmol･m-2･s-1之T5燈每日照光16 h，每穴單株疏植464 plant･m-2，分別以Hoagland養液配方、修改之Hoagland養液配方、山崎氏萵苣養液配方與修改之山崎氏萵苣養液配方栽培，結果Hoagland養液栽培之單株鮮重最佳、葉片硝酸鹽含量最低，‘Gentilina White’分別為4.5 g與215 mg･L-1，‘Island Cos’為2.5 g與25.8 mg･L-1，‘Lollo White’為3.1 g與2278 mg･L-1，‘Red Salad Bowl Improved’為2.7 g與890.7 mg･L-1；且修改之山崎氏萵苣配方顯著提高‘Red Salad Bowl Improved’葉片維生素C含量至111 mg･L-1；四品種中仍以‘Gentilina White’及‘Island Cos’之葉片硝酸鹽含量較低，而‘Island Cos’及‘Red Salad Bowl Improved’之葉片維生素C含量較高。接著於26 ℃密閉型LED室，以光量80 μmol･m-2･s-1之紅光LED (峰值660 nm)、80 μmol･m-2･s-1之藍光LED (峰值448 nm)、50 μmol･m-2･s-1之綠光LED (峰值520 nm)、80 μmol･m-2･s-1紅光LED加80 μmol･m-2･s-1藍光LED、80 μmol･m-2･s-1紅光LED加50 μmol･m-2･s-1綠光LED、80 μmol･m-2･s-1藍光LED加50 μmol･m-2･s-1綠光LED以及80 μmol･m-2･s-1紅光LED加80 μmol･m-2･s-1藍光LED加50 μmol･m-2･s-1綠光LED，每日照光16 h，其中紅藍綠光LED及T5燈栽培之苗菜外觀最佳，而於紅藍綠光LED下栽培三個綠葉品種，其葉片SPAD-502值高於T5燈栽培者。最後於25 ℃密閉型植物工場，以236 μmol･m-2･s-1之T5燈每日照光16 h，在Hoagland養液中添加15、30與45 μmol･L-1矽酸鈉(Na2SiO3)，結果以15 μmol･L-1栽培之‘Gentilina White’、‘Island Cos’、‘Lollo White’及‘Red Salad Bowl Improved’比對照組分別增加單株鮮重18%、14%、13%與13%，硝酸鹽含量亦皆低於2500 ppm。故於密閉型植物工廠栽培萵苣苗菜，建議日/夜溫25 ℃/15 ℃，使用210 μmol･m-2･s-1之80 μmol･m-2･s-1紅光LED加80 μmol･m-2･s-1藍光LED加50 μmol･m-2･s-1綠光LED、或236 μmol･m-2･s-1之T5燈，每日照光16 h，每穴單株疏植之密度464 plant•m-2，添加15 μmol･L-1矽酸鈉之Hoagland配方養液，‘Gentilina White’及‘Island Cos’適用電導度1.0 dS･m-1、‘Lollo White’及‘Red Salad Bowl Improved’適用1.1 dS･m-1。

關鍵字

植物工廠；萵苣苗菜

並列摘要

Plant factory is an environmentally controlled structure for growing crops. Pesticide-free, low bacteria counts and high-yielding fresh vegetables can be hydroponically produced year round in the plant factory. The advantages of commercially producing baby leaf lettuce include short growing period, ready to eat and minimal processing. Baby leaf lettuce ‘Gentilina White’, ‘Island Cos’, ‘Lollo White’ and ‘Red Salad Bowl Improved’ were used as the experimental materials in this research to study the optimal nutrient formula and environmental conditions. In the growth chamber with day/night temperature of 25 ℃/20 °C, white light emitting diodes (light-emitting diode, LED) of photosynthetically active radiation (PAR) 200 μmol•m-2•s-1 were daily illuminated for 16 h. Planting density of 464 plant•m-2 with 1 seedling per sponge block was applied to test the optimal concentration of Hoagland nutrient formula. Among 0.3, 0.5, 0.7, 0.9, 1.0, 1.1 and 1.2 dS･m-1 electrical conductivities, 1.0 dS･m-1 was suatible for ‘Gentilina White’ and ‘Island Cos’, and 1.1 dS･m-1 for ‘Lollo White’ and ‘Red Salad Bowl Improved’. Baby leaf lettuce was grown in Hoagland nutrient solution with planting densities of 929 and 1858 plant•m-2 with 2 seedlings per sponge block, and 464 and 929 plant•m-2 with 1 seedling per sponge block. Density of 464 plant•m-2 with 1 seedling per sponge block showed higher biomass of 1.8 g･plant-1 in ‘Gentilina White’, 2.4 g･plant-1 in ‘Island Cos’, 3.0 g･plant-1 in ‘Lollo White’ and 3.1 g･plant-1 in ‘Red Salad Bowl Improved’. In 25 ℃ plant factory, with Hoagland nutrient solution and 464 plant･m-2 density, T5 fluorescent lamps of 236, 200 and 164 μmol･m-2･s-1 PAR were daily illuminated for 16 h. ‘Gentilina White’, ‘Island Cos’, ‘Lollo White’ and ‘Red Salad Bowl Improved’ exhibited better biomass of 3.0, 2.4, 1.8 and 1.4 g･plant-1, respectively, under 236 μmol･m-2･s-1. Leaf number, length and SPAD-502 value were also the highest, and nitrate concentration the lowest with 413, 435, 2157 and 2348 ppm, respectively. Then in the plant factory with T5 fluorescent lamps of 236 μmol•m-2•s-1 illuminated for 16 h daily, 25 ℃/20 ℃, 25 ℃/15 ℃ and 20 ℃/20 ℃were treated. The fresh weight under 20 ℃/20 ℃ was the lowest. ‘Gentilina White’ and ‘Red Salad Bowl Improved’ showed higher oBrix under 25 ℃/15 ℃ than under 25 ℃/20 ℃. In the plant factory with T5 lamps of 236 μmol•m-2•s-1 illuminated for 16 h daily at 25 ℃/20 ℃, Hoagland solution, modified Hoagland solution, Yamazaki solution and modified Yamazaki solution were treated with density 464 plant･m-2 and 1 seedling per sponge block. The plant biomass from Hoaland solution was the highest and nitrate concentration the lowest, which were 4.5 g･plant-1 and 215 mg･L-1 in ‘Gentilina White’, 2.5 g･plant-1 and 25.8 mg･L-1 in ‘Island Cos’, 3.1 g･plant-1 and 2278 mg･L-1 in ‘Lollo White’, 2.7 g･plant-1 and 890.7 mg･L-1 in ‘Red Salad Bowl Improved’, respectively. ‘Red Salad Bowl Improved’ in modified Yamazaki solution exhibited higher vitamin C content (111 mg･L-1). The nitrate concentrations in ‘Gentilina White’ and ‘Island Cos’ were lower, and the Vitamin C contents in ‘Island Cos’ and ‘Red Salad Bowl Improved’ were higher. Plants were hydroponically cultured at 26 ℃ with 80 μmol･m-2･s-1 red (R) LED (peak wavelength 660 nm), 80 μmol･m-2･s-1 blue (B) LED (448 nm), 50 μmol･m-2･s-1 green (G) LED (520 nm), 80 μmol･m-2･s-1 R LED + 80 μmol･m-2･s-1 B LED, 80 μmol･m-2･s-1 R LED + 50 μmol･m-2･s-1 G LED, 80 μmol･m-2･s-1 B LED + 50 μmol･m-2･s-1 G LED, and 80 μmol･m-2･s-1 R LED + 50 μmol･m-2･s-1 G LED + 80 μmol･m-2･s-1 B LED. The appearance was the best under RGB LED and T5. But SPAD-502 value was higher in plants under RGB LED than in T5 fluorescent lamps among green-leaf cultivars. In plants factory with 25 ℃ and T5 fluorescent lamps of 236 μmol•m-2•s-1 illuminated for 16 h daily, Hoagland nutrient solution was added with 15, 30 and 45 μmol•L-1 Na2SiO3. Fifteen μmol•L-1 Na2SiO3 could significantly increased 18% of the biomass in ‘Gentilina White’, 14% in ‘Island Cos’, 13% in ‘Lollo White’ and 13% in ‘Red Salad Bowl Improved’. The nitrate concentrations were below 2500 ppm. In conclution, it is recommended that the optimal conditions for hydroponically producing baby leaf lettuce(Lactuca sativa L.) in the closed-type plant factory are 25 ℃/15 ℃, 80 μmol•m-2•s-1 red LED plus 80 μmol•m-2•s-1 blue LED plus 50 μmol•m-2•s-1 green LED or 236 μmol•m-2•s-1 T5 fluorescent lamps illuminated for 16 h daily, density of 464 g･plant-1 with 1 seedling in each sponge block, and Hoagland nutrient solution added with 15 μmol•L-1 Na2SiO3. EC 1.0 dS･m-1 is suatible for ‘Gentilina White’ and ‘Island Cos’, and 1.1 dS･m-1 for ‘Lollo White’ and ‘Red Salad Bowl Improved’.