AIR AND ROOT-ZONE TEMPERATURE EFFECTS ON THE GROWTH AND YIELD OF AMERICAN GINSENG

American ginseng seedlings were grown in growth chambers at a continuous 10.degree., 15.degree., 20.degree. and 23.degree. C, and seedlings and 3-year-old roots in a greenhouse with mean air temperatures of 13.degree. C at night and 21.degree. C during the day, and root-zone temperatures of 13.degree., 18.degree. and 23.degree. C. Maximum shoot and root dry weights (economic yield) in the growth chambers were at 15.degree. C. Leaflet growth was not influenced by temperature, but stem growth was reduced linearly over the temperature range 10.degree. to 23.degree. C. Root growth was particularly slow at 10.degree. C. In the greenhouse the fastest initial growth rate of roots was at a root-zone temperature of 23.degree. C. However, maximum leaflet area, shoot and root dry weight of seedlings was at 18.degree. C.