Effect of Light Conditions on Photoinhibition of Ginseng and Tobacco

Photoinhibition studies were conducted with ginseng (Panax ginseng) grown under shade and tobacco (N. tobaccum cv. Bulgaria) grown under full sunlight. The plants were exposed to light intensity of 580, 1280, 1770, 2580 E/㎡/sec in normal air for 3.6 9 hours. Light saturation of ginseng was observed at 550 E/㎡/sec and that of tobacco was at 1600 E/㎡/sec. Tobacco exposed to high light intensity and long duration of light irradiation didn't show entire reduction in photosynthetic capacity. But in ginseng, 20.3% of photosynthesis was reduced in light intensity of 2,580 E/㎡/sec during 9 hours. Light response in photosynthesis differed considerably between tobacco and ginseng, and ginseng exposed to high light intensity showed remarkable reduction in photosynthesis. The extent of photoinhibition of ginseng was dependent on the length of exposure to the high light intensity. Stomatal resistance of ginseng seemed not to be changed by photoinhibition but mesophyll resistance was increased.