参棚透光率对西洋参叶片光合作用的影响

研究了参棚透光率与西洋参叶片净光合速率之间的关系．结果表明，西洋参叶片光饱和点、净光合速率及其日变型均随参棚透光率的不同，存在一定的差异．4年生西洋参叶片在12％、30％、42％3种透光率下(气温29．0℃左右)，光饱和点分别为171．0、323．0和429．0μmol·m^-2·s^-1，净光合速率最大值为6．54mg·dm^-2·h^-1(CO2)，出现在透光率为30％的参棚下；3年生西洋参在透光率不超过25．8％的参棚下，叶片净光合速率日变化呈单峰型，透光率大于25．8％时，呈双峰型，参叶“光合午休”现象明显．单相关分析表明，光量子通量密度是影响西洋参净光合速率的主要因子；回归分析结果表明，各影响因子对参叶净光合速率的综合影响显著．

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.