Difference between Day and Night Temperature (DIF) and Light Intensity Affect Growth and Photosynthetic Characteristics of Panax ginseng Meyer Sprouts

Abstract

Panax ginseng sprouts (PGS) have the advantage of requiring short-term cultivation while maintaining higher ginsenoside contents than traditional ginseng seedlings. It is feasible to improve their yield capacity by manipulating physical factors such as temperature and light. This study therefore investigated the effects of the DIF (difference between day and night temperature) and LI (light intensity) on the growth and photosynthetic characteristics of PGS. To this end, four DIF treatments (18/22 °C, 20/20 °C, 22/22 °C, 22/18 °C), corresponding to two LI regimes (20 PPFD, 200 PPFD), were applied on one-year-old ginseng rootlets in closed-type plant production systems (CPPSs). The PGS had distinctly different responses to the eight treatments. In particular, we found that negative DIF considerably hampered the growth and development of roots, shoots, leaves, and photosynthesis, regardless of the LI considered. The PGS treated with 20/20 °C combined with 20 PPFD displayed the best root growth, shoot development, leaf area, as well as optimal photosynthetic ability. On the other hand, we further showed that the root growth rate was positively correlated with the stem diameter, leaf traits, and photosynthetic ability, whereas it was negatively correlated with the petiole length, stem length, and shoot length. Collectively, 20/20 °C combined with 20 PPFD was the optimal condition in the current study, and may be regarded as a successful strategy for large-scale productions of PGS.