인공광 이용형 식물공장 내 고품질 결구 양상추 생산을 위한 적정 품종 및 광 환경 조건 구명 = Optimization of Cultivar and Light Environment for the Production of High Quality Head Lettuce in Closed-type Plant Factory System

다국어 초록 (Multilingual Abstract)

Cultivation in closed-type plant factory system of crisp head lettuce was tried to solve unstable production and low quality achievement which is mainly caused by prevalent physiological disorders and disease infection in hot summer season. Three separate experiments were conducted to select suitable cultivars and to optimize light and temperature environments in order to produce high quality crisp head lettuce under closed environment in this study. Five commercial crisp head lettuce cultivars (‘Adam’, ‘Early Impulse’, ‘Sensation’, ‘Arirang’, and ‘Manchu’) were grown on DFT beds in closed-type plant factory system under three different fluorescent light intensity conditions (150, 200, and 250 µmol∙m-2∙s-1) and six light quality combinations using red, blue (R:B=25:75, 45:55, 65:35, PPF ratio, while W is maintained to 100 µmol∙m-2∙s-1), and white (R:B:W=16:4:180, 40:10:150, 64:16:120, PPF ratio) LEDs for 60 days under the same environmental conditions (200 µmol∙m-2∙s-1, 50±10 % RH, 12 h day length, and 18/16ºC (0-30 DAT) →18/14ºC (30-60 DAT) air temperature). Separately, the effect of three different light intensity was reinvestigated under relative high air temperature condition of 22/18 ºC (0-30DAT) →18/16 ºC (30-60 DAT) to elucidate the temperature effect on head formation process. Key growth parameters including head formation rate and tip burn incidence were measured in all the separate experiments. All the cultivars exhibited statistically higher growth rates and head formation processes in 200 or 250 µmol·m-2·s-1 compared to 150 µmol·m-2·s-1 under high and low temperature condition, showing cultivar-specific differences in growth pattern to light intensity. The head formation was only observed in two cultivars of ‘Sensation’ and ‘Adam’ in high temperature while pre-screened three cultivars (‘Sensation’, ‘Adam’, and ‘Manchu’) all moved to head formation process in low temperature condition. The detailed head formation characteristics were dependent on cultivars and light intensity dependent head formation rate changes were also observed; Only two cultivars of ‘Sensation’ and ‘Adam’ showed normal head formation under the range of 200 and 250 µmol·m-2·s-1. Among the tested cultivars, ‘Adam’ showed middle size with highest density of heads and the head formation was more apparent in low air temperature than high temperature condition. Regarding the timing of head formation initiation, the leaf morphology began to fold at 8-10 true leaf stage around from 20 DAT, and then the apparent head formation was observed from 30 days after transplanting, followed by the increase of head density until harvest (60 DAT). In addition, active conversion of high red into high blue light ratio (30 DAT- 60 DAT) makes positive effect on growth and head formation of crisp head lettuce, while the white LED light does not promote leaf biomass and head formation. The tip burn symptoms were observed in all the cultivars, light intensity, and quality treatments. Through two serial cultivation trials with cultivar and light intensity factors under high and low temperature condition, ‘Sensation’ and ‘Adam’ could be selected as potentially applicable cultivars in terms of the stable head formation under closed-type plant factory system and superior head quality under 200 or 250 µmol∙m-2∙s-1 PPF conditions. These studies might supply valuable information on the production of crisp head lettuce in closed-type plant factory system, critically focusing on facilitating the sound head formation process under diverse ranges of light and temperature treatments.

목차 (Table of Contents)

• Abstract 1
• Introduction 4
• Literature Review 7
• Materials and Methods 13
• Results 22
• Discussion 53
• Conclusion 59
• Literature cited 61
• Abstract in Korean 70