Effects of Different Air Temperature and Light Quality / Intensity on Growth and Folate Biosynthesis in Leaf Lettuce

The paper aimed to explore the effects of different air temperature and light irradiation conditions on growth and folate biosynthesis in leaf lettuce using a plant growth cabinet with LEDs. Leaf lettuce was cultivated under combination conditions with 3 different air temperatures (20℃, 25℃ and 28℃) and 4 different light irradiations (photosynthetic photon flux density [PPFD] of 150 mol·m-2·s-1 [P150]/RB, P150/RGB, P200/RB and P200/RGB) for 21 days. At the end of the cultivation, growth endpoints including edible portion weight, and folate contents were examined. The experiment results demonstrated significant effects of air temperature and light irradiation conditions on growth and folate biosynthesis in leaf lettuce. We identified the optimal combination condition, 25℃ and P200/RGB, significantly promoting growth and folate biosynthesis in leaf lettuce. The edible portion weight and folate contents in leaf lettuce cultivated under our optimal combination were 15%-62% and 83%-137% greater, respectively, compared to any light irradiation conditions at 20℃, an optimal temperature for conventionally growing leaf lettuce. Addition of green LED to red and blue LEDs maximized leaf lettuce growth and folate biosynthesis. Plant factory with optimal temperature and light irradiation conditions utilizing RGB independent dimming type LED lights is a promising novel agriculture concept maximizing plant growth and critical nutrients such as folate.