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|Title:||光照、溫度與風吹對人工光型植物工場水耕結球萵苣(Lactuca sativa L. var. capitata L.)產量與品質之影響|
Effects of Light, Temperature, and Venting on the Yield and Quality of Hydroponic Iceberg Lettuce (Lactuca sativa L. var. capitata L.) in Artificial Lighting Plant Factory
crisphead lettuce,tipburn,light intensity,photoperiod,air day/night temperature,root temperature,wind blowing,
|Publication Year :||2016|
|Abstract:||結球萵苣(Lactuca sativa L. var. capitata L.)為世界重要的生菜作物，為了在臺灣周年量產結球萵苣，本研究探討於人工光型植物工場水耕結球萵苣‘常利6號’之最適光積值、日夜氣溫、養液溫度及風吹條件。
結球萵苣‘常利6號’自播種後第2 日，以密度661 plant∙m-2育苗；設定光強度200 μmol∙m-2∙s-1且光週期16 h/8 h，於日夜氣溫24 ℃/20 ℃育苗之株形比26 ℃/22℃者緊密，生長比22 ℃/18 ℃者快速，可縮短育苗期3日。而於日夜氣溫24 ℃/20 ℃，當明期延長至20 h且光強度提升為300 μmol∙m-2∙s-1，具四片本葉之15日齡苗最大葉片之SPAD-502 讀值高，並進一步縮短育苗時間3日，於播種後15日即可定植，且葉球形態及產量皆與育苗舊法無顯著差異。
結球萵苣‘常利6 號’以水耕定植於臺灣大學完全密閉型植物工場，栽培密度為14 plant∙m-2，光源為14W 晝白光6500K 螢光燈管；在氣溫21~25 ℃時，光週期16 h/8 h且光強度200 μmol∙m-2∙s-1、以及光週期11 h/13 h且光強度300 μmol∙m-2∙s-1，亦即光積值分別為11.52與1.88 mol∙m-2∙d-1時，於定植42日葉球皆達230 g以上，緊實度皆為16~17 N。在日夜氣溫22.7~25.6 ℃/20.8~21.5 ℃、相對濕度51.9%~64.9%、光積值11.62 ± 0.04 mol∙m-2∙d-1且明期8 h~20 h，於定植42日所有葉球鮮重皆達235 g以上、緊實度18~22 N、密度0.30~0.42 g∙cm-3；而明期14 h~20h下，內葉頂燒症嚴重度超過3 且無市售價值；明期10 h~12 h則約為2；僅有以明期8 h栽培之葉球完全無頂燒症發生。
結球萵苣‘常利6號’在光強度225 μmol∙m-2∙s-1 之28W 晝白光6500K 螢光燈下，以六種日夜溫栽培，包括19 ℃/17 ℃、20 ℃/15 ℃、21 ℃/19 ℃、22 ℃/17 ℃、23 ℃/21 ℃及24 ℃/19 ℃。當日夜溫差為5 ℃時，葉球鮮重與體積皆比日夜溫差2 ℃者大，維生素C與硝酸鹽含量亦皆較高；其中20 ℃/15 ℃組之葉球414 g最重，且內葉頂燒症最輕微，中心柱長5.3 cm，中心柱與葉球高度之比值為0.42；而24 ℃/19 ℃與22 ℃/17 ℃組之內葉頂燒症嚴重度皆大於3。另設定日夜氣溫24 ℃/20 ℃、板面光強度225 ± 25 μmol∙m-2∙s-1且光週期16 h/ 8 h，分別將結球萵苣定植於養液溫度21.7 ℃與19.5 ℃之湛水式迴水系統中，內葉頂燒症嚴重度皆為小於1。‘常利6號’定植於養液溫度21.7 ℃，於定植42日葉球鮮重較19.5 ℃者大，硝酸鹽含量低於700 μg∙g-1 FW，且比養液溫度19.5 ℃與21~24 ℃者皆低。
結球萵苣在氣溫21~26 ℃、光強度220 μmol∙m-2∙s-1 且光週期16 h/8 h環境下栽培，自頂部以1、2 及3 m∙s-1 或自側面以1 m∙s-1全日吹風，葉球鮮重僅約200 g，且皆無法抑制內葉頂燒症發生。
‘常利6 號’於植物工場以降低養液溫度系統(FL14-RT22 處理)或於25 ℃/20 ℃人工氣候室(Sun10-T25 處理)水耕，定植42 日之葉球鮮重分別為293.6 g與335.5 g，雖然皆較土耕組低，但內葉頂燒症嚴重度分別為0.8與3.2，且FL14-RT22組與土耕對照組無顯著差異。水耕組之葉球維生素C、總酚與總可溶性固形物含量皆顯著高於土耕組，而控制養液溫度處理FL14-RT22組之葉球維生素C、總可溶性固形物與硝酸鹽含量皆為最高，分別是265.2 μg∙g-1 FW、2.8 °Brix與1545.8 μg∙g-1 FW。
以厚度0.025 mm之低密度聚乙烯(low-density polyethylene, LDPE)包裝葉球，置於5~6.5 ℃下儲藏7~21日。土耕組葉球儲藏14日及21日，表面皆變黃腐爛，中肋變紅、SPAD讀值顯著降低，總酚含量顯著上升，維生素C無顯著變化；但FL14-RT22 葉球儲藏7~21日，葉球表面與中肋無明顯變色，但儲藏14日葉球之維生素C含量顯著降低，而儲藏21 日總酚含量才顯著提升。
綜之，水耕結球萵苣‘常利6 號’育苗15~18日後，定植於人工光型植物工場光週期9 h/15 h、光強度400 μmol∙m-2∙s-1，且具有湛水式養液溫度22 ℃系統，於氣溫21~26 ℃經42日育成期即可採收，葉球鮮重約300 g。相較於土耕者，其球表較翠綠、不易腐爛，中肋較淺綠、不易褐變，而且內葉頂燒症嚴重度低，葉球維生素C及總酚含量皆較高，且採後置於5~6.5 ℃儲藏14~21日仍具市售價值，有助於量產水耕葉球供應國內鮮食市場，取代臺灣夏季自國外進口之結球萵苣。
Iceberg lettuce (Lactuca sativa L. var. capitata L.) is an important salad vegetable in the world. This research aim at the appropriate daily light integral (DLI), air day/night temperature, root temperature (RT), and venting for producing hydroponic iceberg lettuce in artificial lighting plant factory.
Iceberg lettuce ‘Chang-Li No. 6’ was cultured with density of 661 plant∙m-2 under light intensity 200 μmol∙m-2∙s-1 and photoperiod 16 h/8 h from 2 days after seeding (DAS). Seedlings cultivated at day/night air temperature 24 ℃/20 ℃ were more compact than those at 26 ℃/22 ℃, and grew more rapidly than at 22 ℃/18 ℃ with 3 days shorten to transpalnt. Under light period 20 h and light intensity 300 μmol∙m-2∙s-1, 15 DAS seedlings with 4 true leaves were grown at air temperature 24 ℃/20 ℃, showed higher SPAD-502 value in maximal leaf. Three more days of seedling period was shortened and only 15 days for transplanting. No difference between revised and original seedling raising methods existed on the yield and head appearance.
Iceberg lettuces ‘Chang-Li No. 6’ were transplanted with density 14 plant∙m-2, and grown hydroponically in artificial lighting plant factory in National Taiwan University. Artificial light 6500K cool white fluorescent lamps (FL) of 14W were used. Leafy feads was 230 g of weight and 16-17 N of firmness on 42 days after transplanting (DAT) at air temperature 21-25 ℃, photoperiod 16 h/8 h and light intensity 200 μmol∙m-2∙s-1 or 11 h/13 h and 300 μmol∙m-2∙s-1, with DLI 11.52 and 11.88 mol∙m-2∙d-1, respectively. Under air temperature 22.7-25.6 ℃/20.8-21.5 ℃, relative umidity 51.9%-64.9%, DLI 11.62 ± 0.04 mol∙m-2∙d-1 and light period 8 to 20 h, all heads were higher than 235 g, with firmness 18-22 N, and density 0.30-0.42 g∙cm-3 on 42 DAT. Tipburn severity (TB) of heads were higher than 3 under light period 14-20 h, about TB 2 under 10-12 h, and no tipburn only under 8 h.
Among 6 air day/night temperatures 19 ℃/17 ℃, 20 ℃/15 ℃, 21 ℃/19 ℃, 22 ℃/17 ℃, 23 ℃/21 ℃, and 24 ℃/19 ℃ with 225 μmol∙m-2∙s-1 of 6500K FL 28 W after transplanting, fresh weight and volume of head in 5 ℃ difference of day/night temperatures (DIF) treatments were higher than these in DIF 2℃ treatment. The contents of vitamin C and nitrate were higher in DIF 5℃. At 20 ℃/15 ℃, the head weight 414 g was the highest, TB the least, with core height 5.3 cm and core height/head height ratio of 0.42. TB higher than 3 was scored at air day/night temperature 24 ℃/19 ℃ and 22 ℃/17 ℃. Iceberg lettuces were transplanted in recycled deep flow system (DFT) with nutrient RT 21.7 ℃ and 19.5 ℃ by root cooling system. Under air day/night temperature 24 ℃/20 ℃, light intensity 225 ± 25 μmol∙m-2∙s-1 and photoperiod 16 h/ 8 h, TB was scored less than 1. On 42 DAT, the yield at RT 21.7 ℃ was higher than that at RT 19.5 ℃. Nitrate content at 21.7 ℃ (< 700 μg∙g-1 FW) was less than that at RT 21-24 ℃. Grown under air temperatures 21-26 ℃, light intensity 220 μmol∙m-2∙s-1 and photoperiod 16 h/8 h, head fresh weight was about 200 g, but TB could not be prevented by all-day venting with top wind of 1, 2, and 3 m∙s-1 or side wind 1 m∙s-1.
Iceberg lettuces ‘Chang-Li No. 6’were hydroponically cultivated in artificial lighting plant factory with root cooling system (FL14-RT22 treatment) or in phytotron with air temperature 25 ℃/20 ℃ (Sun10-T25 treatment). On 42 DAT, head fresh weights were 293.6 g and 335.5 g, respectively, lower than that grown in the open field. TB of inner leaves was 0.8 and 3.2, respectively in FL14-RT22 and Sun10-T25. No difference in TB was shown between field-grown and FL14-RT22 lettuce. All iceberg lettuces grown by hydroponics exhibited higher contents of vitamin C, total phenolics, and total soluble solids than field-grown lettuce. FL14-RT22 had the highest contents of vitamin C (265.2 μg∙g-1 FW), total phenolics (2.8 °Brix), and total soluble solids (1545.8 μg∙g-1 FW).
Heads wrapped with 0.025 mm low-density polyethylene were stored at 5-6.5 ℃ for 21 days after harvest (DAH). Head surface of field-grown lettuce became yellowgreen, midrib reddish, SPAD values lower on 14 or 21 DAH. Contents of total penolics increased but vitamin C decreased in heads. However, heads of FL14-RT22 treatment stored for 7 to 21 DAH, head surface and midrib did not change color significantly; vitamin C content decreased on 14 DAH, and total phenolics increased on 21 DAH.
In conclusion, seedling period of iceberg lettuce ‘Chang-Li No. 6’ was 15 to 18 days, and cultivating period about 42 days in artificial lighting plant factory. During the cultivating period, seedlings were grown at light intensity 400 μmol∙m-2∙s-1, photoperiod 9 h/15 h, air temperature 21 to 26 ℃ with deep flow technique (DFT) hydroponics system in the constant nutrient temperature 22 ℃.. Head fresh weight for harvest was about to 300 g. Head surface was green and not easily perishable, and midrib was light green and not easily discolored comparing to field-grown heads. In inner leaves, without any severe TB symptom, and heads were rich in vitamin C and total phenolics. Heads grown by DFT hydroponics were still marketable on 14 to 21 days storage at 5 to 6.5 ℃ after harvest. Hydroponic iceberg lettuce could be hopefully replaced those imported from abroad to Taiwan in summer to supply fresh-cut lettuce in local market.
|Appears in Collections:||園藝暨景觀學系|
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