Effects of Daylength Extension by Red Light in Strawberry Cultivation

BACKGROUND: Many strawberry growers are utilizing daylength extension by using incandescent bulb or fluorescent lamp to break dormancy of strawberry induced by low temperature and short day conditions. Conventional incandescent bulb and fluorescent lamp consume a lot of electricity and have short longevity. Red light known for most efficient wavelength for daylength extension light of short-day plant and long-day plant. This study was conducted to verify the effects of red light to enhance growth and to increase production of strawberry (Fragaria ${\times}$ ananassa Duch. cvs. "Seolhyang") METHODS AND RESULTS: Three red light (660nm) of 0.70, 0.87, and $1.05{\mu}mol/m^2/s$ (PAR) and conventional incandescent bulb of 40 Lux were treated respectively under the pot experiment. All treatment irradiated from 18:00 to 24:00 for 6 hours. Red light treatment tend to increase leaf stem number, flower stem number, weight of flower stem, crown weight, root weight, and leaf area of strawberry then incandescent bulb treatment. In field experiment, red light of $0.7{\mu}mol/m^2/s$ (PAR) and conventional incandescent bulb of 40 Lux were irradiated respectively. Field experiment showed that the leaf number, leaf weight, and crown weight of strawberry increased than those of incandescent bulb control with red LED of $0.7{\mu}mol/m^2/s$ (PAR). Red LED treatment increased the fruit number over 15g than incandescent bulb. Furthermore, red LED treatment decreased fruit number below 15g of strawberry than incandescent bulb treatment. Therefore, We believed that red LED treatment increased marketable fruit number by increment of weight of each fruit. Consequently, marketable fruit number, fruit weight, and fruit production of strawberry were increased than those of incandescent bulb by 5 %, 2.9 %, and 8.5 % respectively, but not showed significantly differences. CONCLUSION: These results presumably due to directly enhanced photosynthesis of strawberry leaves and activated action of Pfr phytochrome form by red light. In conclusion, red LED of 660nm could be used for daylength extension light source to enhance production of strawberry.

적색광에 의한 딸기재배의 일장연장 효과

본 연구는 적색광(660 nm)을 이용한 딸기(Fragaria ${\times}$ ananassa Duch. cvs. "Seolhyang")의 일장연장 처리효과를 구명하고자 수행하였다. 포트실험에서 관행의 백열등 40 Lux와 적색광 0.70, 0.87, $1.05{\mu}mol/m^2/s$ (PAR)에 의한 일장연장 처리는 백열등 처리 보다 적색광 강도가 증가할수록 딸기의 초장, 엽수, 과실무게가 증가하는 경향이었다. 재배포장실험에서 적색 LED $0.7{\mu}mol/m^2/s$ 강도의 일장연장처리는 관행의 백열등 40 Lux 처리 보다 딸기의 엽 생체중, 엽병 생체중, 크라운 생체중과 총 생체중을 유의하게 증가시켰다. 적색 LED 처리가 백열등 처리 보다 딸기의 과실수는 5%, 과실무게는 2.9%, 딸기 수확량은 8.5% 증가시키는 경향이었으나 통계적으로 유의한 차이는 나타내지 않았다. 적색 LED 처리는 백열등 처리보다 상품성 있는 15 g 이상의 딸기과실 수를 증가시키는 경향을 보였다. 따라서 딸기의 일장연장을 위한 광원으로 적색 LED도 이용될 수 있을 것으로 기대되며 향후 관련 연구가 계속 수행되어야 할 것으로 판단된다.