[Effects of different light transmission rate on American ginseng's photosynthesis]

From 1997 to 1998, series of experiments were carried out to study American ginseng's photosynthesis related to light transmission rate of plastic cover. The results showed that American ginseng's light saturation point for photosynthesis was different under the different light transmission rate (LTR) because of shading. At about 29.0 degrees C and under 12%, 30%, 42% LTR, 4-year-old American ginseng's light saturation point were 171.0, 323.0, and 429.0 mumol.m-2.s-1, respectively. The maximum net photosynthesis rate (Pn) was 6.54 mg CO2.dm-2.h-1, which appeared under the shading of 30% LTR. The daily course of 3-year-old American ginseng's Pn changed with LTR. When LTR was less than 25.8%, the daily curves of Pn had a single peak, and when LTR was higher than 25.8%, it had two peaks and the leaf's photosynthesis noon break phenomenon was remarkable. The results of single correlative analysis showed that the dominant factor that influenced Pn was photon flux density (PFD), and the results of plural regression analysis showed that the synthetic effect of all the influencing factors together on Pn was significant.