不同光强下焕镛木和观光木的光合参数变化

 生长在全日光强下的焕镛木(Woonyoungia septentrionalis)和观光木(Tsoongiodendron lotungensis)幼树叶片的最大光合速率、表观量子产率和光能转换效率均较生长在40%和20%日光强的高。当生长光强从全日光强降低至40%日光强时，焕镛木的表观量子产率和光能转换效率分别降低13.1%和6.3%，而观光木则相应分别降低23.8%和33.4%。生长光强降低至40%日光强时，焕镛木的Rubisco最大羧化速率(Vcmax)未见变化；而最大电子传递速率（Jmax）则降低14.1%，表明Jmax对光强降低的响应较Vcmax敏感。当生长光强从全日光强降低到40%和20%日光强时，观光木的Vcmax分别降低7.7%和31.7%，而Jmax则分别降低9.7%和42%。光强从全日光强降低至40%日光强，焕镛木叶氮在Rubisco和捕光叶绿素蛋白复合体中的分配系数没有明显改变，而叶氮在生物力能学组分中的分配系数降低则较为明显（20.4%），表明生长光强降低对叶氮在光合电子传递链组分分配的影响较在Rubisco的大。结果表明，焕镛木表现阳生树种特性，在迁地保育中宜选择向阳小生境种植，而观光木较耐荫，可种植在较遮荫的环境。

CHANGES OF LEAF PHOTOSYNTHETIC PARAMETERS IN LEAVES OF WOONYOUNGIA SEPTENTRIONALIS AND TSOONGIODENDRON LOTUNGENSIS UNDER DIFFERENT GROWTH-IRRADIATION

Higher maximum photosynthetic rate, apparent photosynthetic quantum yield and the efficiency of light energy conversion were observed in leaves of saplings of W. septentrionalis and T. lotungensis at full as comparison with that at 40% or 20% daylight. As light intensity decreased from full to 40%, apparent photosynthetic quantum yield and the efficiency of light energy conversion declined by 13.1% and 6.3% for W. septentrionalis, respectively and by 23.8% and 33.4% for T. lotungensis, respectively. Similar maximum carboxylation rates of Rubisco (V cmax ) were found in leaves of W. septentrionalis grown at full and 40%. However, maximum rate of photosynthetic electron transport decreased by 14.1% in decreasing light level from full to 40%. Decreasing ratio between J max and V cmax was also observed. It means that response of J max to decreasing light intensity was more sensitive than that of V cmax . The relative values were 7.7% and 31.7% for V cmax respectively, and 9.7% and 42% for J max respectively, in T. lotungensis, as light intensity decreased from full to 40% and 20%. The partitioning coefficient for leaf nitrogen in Rubisco (P R) and the fraction of leaf nitrogen in thylakoid light harvesting components (P L) were almost the same in W. septentrionalis with decreasing from full to 40%. And the partitioning coefficient for leaf nitrogen in bioenergetics (P B) decreased by 20.4% with decreasing light intensity. Whereas, in T. lotungensis, P R and P B were declined significantly. With decreasing light intensity. The results may suggest that W. septentrionalis would be a sun plant for which an open site would be considered the most optimizing environment for trans plantation and the shade-tolerant plant of T. lotungensis which adapts to a more shade environment.