부산대학교 도서관

This study investigated the eff ects of constant light and alternating relatively high-intensity (500 μmol m −2 s −1 ) and lowintensity(150 μmol m −2 s −1 ) red–blue LEDs (4R:1B) on the biomass production and quality of hydroponic purple-leaf lettuce( Lactuca sativa L. cv. ‘Zishan’) in an environmentally controlled plant factory. Four treatments were set up to separate1 h of high light into four diff erent alternating frequencies in a 24-h light−dark cycle (16/8 h): one time (A1), three times(A3), six times (A6), and twelve times (A12). In addition, one constant light treatment with the same daily light integral(DLI, 9.8 mol m −2 per day) as other treatments was set as the control (CK, 170 μmol m −2 s −1 ). The results indicated thatA6 signifi cantly reduced shoot fresh weight and increased the root–shoot ratio of lettuce compared with CK, but there wasno signifi cant diff erence among other treatments. Alternating light treatments did not promote the accumulation of solublesugar, soluble protein, and phenolic substances compared with CK. Meanwhile, A12 signifi cantly promoted the accumulationof total ascorbate (TA) in lettuce leaves compared with other treatments but decreased ascorbate/TA ratio. Above all, underthe same DLI condition, alternating high and low light did not have obvious positive eff ects on biomass production and theaccumulation of nutrient substance in lettuce under constant light was better than that under alternating light. Therefore,compared with the fl uctuating radiation with the same DLI, constant radiation is a better choice for lettuce production.