【摘要】 喜树 (Camptotheca acuminata)为中国特有树种 ,因其次生代谢产物喜树碱具有抗癌作用而闻名。通过用黄色、红色、蓝色 3种滤光膜对温室栽培的喜树幼苗进行遮光处理 ,研究了不同光照环境下喜树幼苗叶片生物量、叶绿素含量、光合作用和喜树碱含量的差异。结果表明在 30 d的遮光过程中 ,红膜和蓝膜遮光明显导致幼苗叶片生物量降低 ,黄膜遮光下幼苗叶片生物量在处理后 2 5 d才表现明显降低。不同滤光膜下幼苗叶片叶绿素含量先降低然后升高 ,遮光幼苗的叶绿素 a/ b明显低于日光幼苗。幼苗日最大净光合速率的顺序是 :日光 >黄膜 >红膜 >蓝膜。处理后第 2 0天 ,不同滤光膜下幼苗的光饱和光合速率 (Amax)、光饱和点 (Is)、光补偿点 (Ic)、最大表观量子效率 (AQYmax)都不同程度的低于日光幼苗。处理后第 10天至第 30天 ,遮光幼苗叶片喜树碱含量均显著高于日光下幼苗 ,以蓝膜下幼苗的喜树碱含量最高。蓝膜和黄膜下幼苗的喜树碱产量在后期处理中显著高于日光下幼苗 ,蓝膜下幼苗喜树碱产量在第 30天最高 ,是日光下幼苗的 2 .4 9倍。红膜下幼苗的喜树碱产量在第 10天后与日光下幼苗差异不显著。通过滤光膜遮光促进喜树碱在幼苗叶片中的积累 ,提高了叶片喜树碱产量 ,对喜树碱的生产实践有一定的意义更多还原

【Abstract】 Camptotheca acuminata Decaisne （Nyssaceae） is a native Chinese tree that produces camptothecin （CPT）, a pentacyclic quinoline alkaloid, which is known for its remarkable inhibitory activity against tumour cells. To investigate the effects of shading on the biomass, chlorophyll content, photosynthesis and CPT content on leaves of C. acuminata, the seedlings of C. acuminata with 4 pairs of leaves were shaded by yellow, red, and blue film in plots in a greenhouse. The resulting relative light intensity were 60.69%, 51.76%, and 26.96% compared to the full sunlight respectively. The biomass of leaves, chlorophyll, photosynthesis and CPT content in leaves were measured on the 5^th, 10^th, 15^th, 20^th and 25^th day respectively. Light-response curves were measured on Day 20. The biomass accumulation of the leaves is significantly inhibited by the shade of yellow, red or blue film. The inhibition degree varies according to light quality and light intensity. The degree of inhibitions of the red film and blue film are gradually increased over 30 days of shade treatment; however the inhibition of yellow film does not approach significance until the 25^th day of treatment. The kinetics of chlorophyll contents in the leaves shows that total chlorophyll contents under various films are lower than those in full sunlight in the first five days. The contents increase gradually after ten days, and become higher than those in sunlight after fifteen days of the treatment. The ratio of chlorophyll a and chlorophyll b contents in the shaded leaves is consistently lower than that in sunlight over the study duration. The chlorophyll content in shaded leaves is quite different among these three films, and does not show regular characteristics. The maximum net photosynthesis rates of all shaded seedlings decrease over time and being to become lower than that in sunlight around Day 5 of the treatment and is much less after day 10. The order of the maximum net photosynthesis rates from the highest to the lowest is under the condition of sunlight, yellow film, red film and blue film （No obvious difference between the red film treatment and the blue film treatment is found）. After 20 days of treatment, the photosynthesis rate of light-saturated point (A_max), light-saturated point （I_s）, light-compensated point （I_c）, maximum apparent quantum yield (AQY_max) of shaded seedlings by various films are all lower than that in sunlight to different degrees. The A_max, I_s, I_c and AQY_max of seedlings under the yellow film treatment are 80.86%,61.01%,26.66% and 81.35% of those in sunlight respectively. The I_c of seedlings with the red film treatment is lower than that with the yellow film treatment, A_max, I_s and AQY_max however does not show obvious differences. The A_max, I_s and AQY_max of seedlings with the blue film treatment is lower than that with yellow and red film treatments, eventhough but I_c is higher. The CPT content in leaves of all shaded seedlings shows no significant difference in the first five days of treatment from that in sunlight, but is remarkably increased and become higher from the 10^th day to the 30^th day of treatment. The leaves treated with blue film for 30 days have the highest CPT content, whereas the leaves treated with red and yellow films have similar CPT content. The CPT yield in leaves treated with blue and yellow films increases significantly and become higher than that in sunlight after ten days of treatment. The CPT yield under the red film is higher than that of sunlight only around day ten of treatment. The highest CPT yield is obtained under the blue film around Day 30 of treatment, which is 2.49 times higher than that in sunlight. CPT yield under the red film treatment, however, is higher than that in sunlight only in Day 10, and no obvious difference is observed in other periods. The above results demonstrate that the shade treatment with films, especially blue film, accelerate the accumulation of CPT in the leaves of seedlings, which may have practical significance in更多还原