不同光照强度对西洋参光合特性,营养成分和产量的影响

在２１．６％自然光强下生长的西洋参叶片，光合作用的光饱和点和光补偿点皆比１１％自然光强下的高．在恒定条件下，光合作用最适温度为２８℃．２１．６％自然光强下的光合产物，较多地分配到根部，１１％自然光强下则分配到果实中的高．光合速率在一定范围内随透光强度的增加而提高，以透光３０％的叶片为最高．其日变化呈双峰曲线．叶绿素含量在一定范围内随光强的增加而降低，叶绿素ｂ含量的变化亦为同样趋势．叶片结构以弱光和强光相比，在上表皮角质层花纹、下表皮气孔数、叶肉细胞形状、叶绿体数及其基粒片层结构都有明显差别．参的产量随光强的增加而显著增加，但以透光３０％时增长幅度最大，４０％时增长变小．根中总皂苷和氨基酸含量在一定范围内随光强而增加，至透光４０％时又下降．

Effect of light intensity on photosynthetic characteristics, nutritive components and yield of American ginseng

The photosynthetic saturation and compensation points of American ginseng at 21. 6K of natural light intensity(NLI)are higher than those at 11% of NLI,28C is"the optimum temperature for photosynthesis of American ginseng..its photosynthetic products are mainly distributed in roots at ZI,6% of NLI and in fruits at 11% of NLI. The photosynthetic rate increases with increasing light intensity,reaches the maximum at 30N of NLI,and appeares to be a double peak curves during a day.The chlorophyll content of leaf reduces with increasing light intensity when NLI is higher than 20%,and the same for chlorophyll b content. In addition I the stoma number on lower surface of leaf,cuticle figure on upper surface of leaf,chloroplasts number and thylakoid structure are significantly different under higher and lower light intensities.The contents of saponin and amino acid in root of American ginseng and its yield are increased with increasing light intensity,being the highest at 30% of NLI and decreases at 40% of.NLI.