Influence of air temperature on yield and phytochemical content of red chicory and garland chrysanthemum grown in plant factory

This study was conducted to improve the yield and quality of red chicory (Cichorium intybus L.) and garland chrysanthemum (Chrysanthemum coronarium L.) grown in a plant factory where fluorescent lamps were used as an artificial light source. Seeds of a chicory ‘Juck’ and garland chrysanthemum ‘Joongyupssuckgot’ were sown in a peat-lite germination mix. Twenty-day old seedlings with roots being washed off were anchored on a styrofoam board and were grown in hydroponics for 30 days. Plants were exposed to one of the three different air temperature regimes (20, 25, and 30°C during the day combined with 18°C during the night) which were being monitored with a sensor at 30 cm above the plant canopy. In all treatments, light intensity was maintained at 200 ± 20 μmol·m−2·s−1, day length was 12 hours, and relative humidity was 50–80%. Electrical conductivity (EC) and pH of the nutrient solution were 2.0 ± 0.2 dS·m−1 and 6.5–7.0, respectively, in all treatments. Increase in fresh weight was observed in chicory, but not in garland chrysanthemum, in both 25 and 30°C as compared to 20°C. Photosynthetic capacity and ascorbic acid content of chicory leaves were higher at 25°C than in other temperatures. In garland chrysanthemum, photosynthetic capacity was the greatest in both 20 and 25°C, while ascorbic acid content was the greatest in 25°C. Also plants grown at 25°C had the greatest contents of total phenol and flavonoid in both chicory and garland chrysanthemum. Hence, the optimum temperature appears to be 25°C for growing both chicory and garland chrysanthemum in the plant factory with fluorescent light as the sole souse of light.