去遮荫后东北红豆杉幼苗和幼树光合特性对比

Photosynthesis and Chlorophyll Fluorescence Characteristics of Seedlings and Saplings of Taxus cuspidata After Removing Shade

【目的】对比去遮荫后东北红豆杉幼苗和幼树叶片光合与荧光特性,揭示人工培养东北红豆杉幼苗在强光下发生光抑制的原因,为东北红豆杉人工栽培提供理论依据。【方法】以生长在遮荫条件下的东北红豆杉幼苗和幼树为试验材料(遮荫后光强为自然光强的40%),去除遮荫使幼苗和幼树暴露在自然强光条件下28天后,测定幼苗和幼树叶绿素含量、光合速率特性和叶绿素荧光特性。【结果】去遮荫后幼苗和幼树叶绿素含量无显著差异,幼树类胡萝卜素含量显著高于幼苗叶片,而幼树Chl/Cars低于幼苗叶片。幼苗叶片最大光合速率仅为幼树叶片的70%,幼苗具有较低的光补偿点和光饱和点,但表观量子效率(AQY)较高。幼苗叶片处于自然光照条件,叶片的羧化效率(CE)、CO2和光强均饱和下的最大光合速率(Amax)和Ru BP再生速率相对较低。强光诱导下,幼树叶片光合速率在25 min左右达到最大值,而幼苗叶片则需要为50 min,幼苗暗反应启动较慢。叶绿素荧光诱导曲线表明,在强光条件下,幼树叶片的实际光化学效率(ΦPSⅡ)和非光化学猝灭(NPQ)在较短时间内即可达到最大值,而幼苗叶片则需要相对较长的时间。荧光对不同光强相应曲线表明,幼苗叶片的ΦPSⅡ随光强增加而迅速降低,而幼树叶片则下降较慢。幼树叶片的NPQ随着光强增加而增加,而幼苗叶片的NPQ则在相对较低光强水平就达到最大值,幼苗叶片热耗散能力较低。【结论】幼苗叶片较低的光合速率产生相对较多的过剩能量,同时其叶片在高光强下的热耗散能力较低,这是幼苗与幼树相比不适应自然强光和产生光抑制的主要原因。

【Objective】In this study,Photosynthesis and chlorophyll fluorescence characteristics of seedling and sapling leaves of Taxus cuspidata were studied to explore the reasons for the photoinhibion of seedlings after removal of shading,which provide would theoretic basis for the development of Taxus cuspidata cultivation in Northeast China. 【Method】Seedlings and saplings of Taxus cuspidata grown under shade condition（ approximately 40% of the natural light intensity）were taken as the materials. They were moved to full sunlight for 28 days before the experiment was carried out. Then differences of pigment,photosynthesis and chlorophyll fluorescence characteristics of seedling leaves and sapling leaves were measured.【Result】 The result showed that there was no significant difference between seedling leaves and sapling leaves in chlorophlly content. Sapling leaves had a higher content of cartotenoid and a lower value of Chl/Cars significantly. The maximum photosynthetic rate of seedling leaves was only 70% of that of sapling leaves after 28-day full sunlight. Seedling leaves had a lower light compensation point and light saturation point,but apparent quantum yield of photosynthesis（ AQY） was higher. In this case,more excessive energy was produced in seedling leaves under full sunlight condition. Meanwhile,compared within sapling leaves,carboxylation efficiency（ CE）,regeneration rate of Ru BP and Amaxin seedling leaves were lower as well. Theses results indicated that the activity of Rubisco enzyme and the assimilationability of CO2 in seedling leaves were relatively lower. Seedling leaves and sapling leaves of T. cuspidata showed different photosynthetic responses to high light intensity in a short period. The sapling leaves reached the maximum photosynthetic rate in about 25 min under high light,while seedling leaves reached the maximum photosynthetic rate in about 50 min.From low light to high light,actual photochemical efficiency（ ΦPSⅡ） and non-photochemical quenching（ NPQ） of sapling leaves reached their maximum values in a shorter time as compared with those of seedling leaves. In addition,the ΦPSⅡof seedling leaves reduced with the increase of PFD,while that of sapling leaves decreased slightly. Moreover,NPQ of sapling leaves reached a relatively higher level with the increase of PFD,while seedling leaves attained their maximum value with a low light intensity.【Conclusion】 A lower photosynthetic rate of the seedlings resulted in relatively excessive light energy,which made seedling leaves susceptible to photoinhibition after changing to full sun light.