PHOTOSYNTHETIC RESPONSES TO PPF, TEMPERATURE AND HUMIDITY IN PANAX GINSENG PLANTS
Panax ginseng is one of the most popular herbs in the Chinese pharmacopoeia, originated in thick forests of cold mountainous areas from north China, the Korean peninsula and Russian Siberia. Ginseng likes cold, dark and wet weather and may be killed under high temperature, strong light or drought conditions. It is well known that the optimum conditions for ginseng cultivation include a temperature of 10°C yearly average and 20°C during the summer, precipitation of 700-2,000 mm yearly and diffused lighting at 8% of the intensity of natural outside light. However, in plant physiology, it is not clear enough how the leaf photosynthesis (PN) responds to light, temperature and air humidity. Therefore, in the present study, we analyzed responses of PN in Panax ginseng to changing photosynthetic photon flux (PPF), temperature and ambient humidity. The PN response to changing PPF was modeled by PN=PC(1+e-Ki)-RD, where PC is photosynthetic capacity, i is PPF, RD is respiration rate, and K is a constant with KPC as the maximum quantum use efficiency (YQ). It was found that the maximum of PN reached only 6 µmol m-2 s-1. The light saturation point for PN in ginseng leaves was as low as 200 µmol m-2 s-1, which was consistent with the K value in the model equation. The optimum temperature and humidity for PN in ginseng leaves were between 15 and 20°C and 2 kPa, respectively. In addition, organic fertilization was compared with the conventional chemical fertilization for ginseng cultivation. It was found that organic fertilization resulted in higher photosynthetic activities and higher root yield although the shoot dry mass was not so different compared with the chemical fertilization. It is suggested that conditions for ginseng cultivation must meet its original environment, cold, dark and moist with nutrients supplied from organic materials.
Qin, F.F., Du, F.L., Yue, S.S., Xu, H.L., Zhao, A.H., Xu, Q.C. and Tian, C.M. (2011). PHOTOSYNTHETIC RESPONSES TO PPF, TEMPERATURE AND HUMIDITY IN PANAX GINSENG PLANTS. Acta Hortic. 907, 349-354
depression, hysteresis, inhibition, light, modeling, photosynthesis, organic fertilizer