Langenheim J H, Osmond C B, Brooks A, Ferrar P J
Department of Environmental Biology, Research School of Biological Sciences, Australian National University, P.O. Box 475, 2601, Canberra City, ACT, Australia.
Oecologia. 1984 Aug;63(2):215-224. doi: 10.1007/BF00379880.
Seedlings of the Caesalpinoids Hymenaea courbaril, H. parvifolia and Copaifera venezuelana, emergent trees of Amazonian rainforest canopies, and of the Araucarian conifers Agathis microstachya and A. robusta, important elements in tropical Australian rainforests, were grown at 6% (shade) and 100% full sunlight (sun) in glasshouses. All species produced more leaves in full sunlight than in shade and leaves of sun plants contained more nitrogen and less chlorophyll per unit leaf area, and had a higher specific leaf weight than leaves of shade plants. The photosynthetic response curves as a function of photon flux density for leaves of shade-grown seedlings showed lower compensation points, higher quantum yields and lower respiration rates per unit leaf area than those of sun-grown seedlings. However, except for A. robusta, photosynthetic acclimation between sun and shade was not observed; the light saturated rates of assimilation were not significantly different. Intercellular CO partial pressure was similar in leaves of sun and shade-grown plants, and assimilation was limited more by intrinsic mesophyll factors than by stomata. Comparison of assimilation as a function of intercellular CO partial pressure in sun- and shade-grown Agathis spp. showed a higher initial slope in leaves of sun plants, which was correlated with higher leaf nitrogen content. Assimilation was reduced at high transpiration rates and substantial photoinhibition was observed when seedlings were transferred from shade to sun. However, after transfer, newly formed leaves in A. robusta showed the same light responses as leaves of sun-grown seedlings. These observations on the limited potential for acclimation to high light in leaves of seedlings of rainforest trees are discussed in relation to regeneration following formation of gaps in the canopy.
豆科云实属的巴西苏木、小叶云实和委内瑞拉可乐豆的幼苗，它们是亚马孙雨林冠层中的突出树木；南洋杉科贝壳杉属的小叶贝壳杉和大叶贝壳杉的幼苗，它们是澳大利亚热带雨林中的重要组成部分。这些幼苗在温室中于6%（遮荫）和100%全日照（光照）条件下生长。所有物种在全日照下产生的叶片比在遮荫条件下更多，且光照条件下生长的植物叶片每单位叶面积含氮量更高、叶绿素含量更低，比遮荫植物的叶片具有更高的比叶重。遮荫生长的幼苗叶片的光合响应曲线作为光子通量密度的函数，与光照生长的幼苗相比，显示出更低的补偿点、更高的量子产率和更低的单位叶面积呼吸速率。然而，除了大叶贝壳杉外，未观察到光照和遮荫条件下的光合适应现象；光饱和同化率没有显著差异。光照和遮荫生长的植物叶片中的细胞间二氧化碳分压相似，同化作用更多地受到叶肉内在因素的限制而非气孔的限制。对光照和遮荫生长的贝壳杉属植物的同化作用作为细胞间二氧化碳分压的函数进行比较，结果表明光照条件下生长的植物叶片的初始斜率更高，这与更高的叶片含氮量相关。在高蒸腾速率下同化作用降低，当幼苗从遮荫转移到光照条件下时观察到大量光抑制现象。然而，转移后，大叶贝壳杉中新形成的叶片显示出与光照生长的幼苗叶片相同的光响应。结合冠层形成间隙后的更新情况，讨论了关于雨林树木幼苗叶片对高光适应潜力有限的这些观察结果。
