Growth control of Platycodon grandiflorum seedling using difference between day and night temperatures

Abstract

Platycodon grandiflorum has been used as herbal medicine in Asia that is effective in anti-inflammatory, anti-cancer, anti-oxidant, and anti-obesity. In the Republic of Korea, the consumption of P. grandiflorum is increasing as not only herbal medicine but also an ingredient in cooking. As the consumption of P. grandiflorum increases, the need for plug seedling technology to mass produce uniform-sized seedlings has increased. Since plug seedlings are grown in a dense environment, plant growth regulators (PGRs) are used to inhibit overgrowth. Nevertheless, it has been reported that the difference between day and night temperatures (DIF) can also effectively control overgrowth without causing environmental contamination or phytotoxicity issues associated with PGRs. This study was conducted to investigate the effect of DIF on the morphogenesis of P. grandiflorum plug seedlings. Seeds were disinfected with hydrogen peroxide and sown in the commercial growing medium. After sowing, the photoperiod and light intensity of the plant growth chamber were set at 12/12 h (day/night) and 250 µmol m-2 s-1, respectively. DIF was set at 30/20°C (+10 DIF), 25/25°C (0 DIF, control), and 20/30°C (-10 DIF). At 55 days after sowing, plant height and internode length of the +10 DIF were significantly longer than those of the other. The fresh weight and leaf area of the 0 DIF were significantly higher than others. On the other hand, the -10 DIF led to a shortened plant height and internode length, but it also showed leaf chlorosis and the lowest shoot and root growth compared to the others. The results of this study can be used as primary research data for the growth control of P. grandiflorum in plug seedling. © 2024 International Society for Horticultural Science. All rights reserved.