Yamashita Naoko, Ishida Atsushi, Kushima Hiromichi, Tanaka Nobuyuki
Forestry and Forest Products Research Institute (FFPRI), P.O. Box 16, Tsukuba Norin Danchi, Ibaraki 305-8687, Japan, Japan.
Oecologia. 2000 Nov;125(3):412-419. doi: 10.1007/s004420000475. Epub 2000 Nov 1.
Bischofia javanica Blume, an exotic tree, dominates many forest areas of the Bonin Islands in the western Pacific of Japan. The aim of this study was to test the hypothesis that the success of B. javanica (a mid-successional plant species) is related to its high acclimation capacity to sudden light increase due to canopy gap formation. We compared its ecophysiological response to simulated canopy opening with those of native species of different successional status: Trema orientalis Blume, Schima mertensiana (Sieb, et Zucc.) Koidz, Elaeocarpus photiniaefolius Hook.Et Arn. and Ardisia sieboldii Miquel. In all species, transfer of leaves developed in shade (5.3% of full sun) to full sun resulted in a substantial initial reduction in the dark-adapted quantum yield of photosystem II (Fv/Fm). T. orientalis, a pioneer plant species, showed the least reduction (38%), whereas E. photiniaefolius and A. sieboldii, both late-successional plant species, demonstrated large reductions (about 80%). In all four native species, Fv/Fm in shade leaves gradually recovered following transfer, but B. javanica recovered more fully and rapidly than the other species. Unlike Fv/Fm, the chlorophyll content in all species did not recover following the initial decline. This indicates that the recovery of quantum yield (Fv/Fm) was independent of the reduction in chlorophyll. Among all the species, B. javanica showed the highest (1) increase in maximum photosynthetic rate of shade leaves after transfer, (2) production of newly formed sun leaves, and (3) increase in relative growth rate. Ecophysiological characters of B. javanica in simulated canopy openings indicated rapid photosynthetic acclimation in existing shade leaves by minimizing photoinhibition and a rapid deployment of new sun leaves with high photosynthetic capacity. Because its habitats on these Pacific Islands are prone to typhoon disturbance, the successful invasion of B. javanica may lie in the congruence of its acclimation potential and the frequent gap events.
人面子，一种外来树种，在日本西太平洋的小笠原群岛的许多林区占主导地位。本研究的目的是检验以下假设：人面子（一种演替中期的植物物种）的成功与其对林冠空隙形成导致的光照突然增加的高适应能力有关。我们将其人理生理反应与不同演替状态的本地物种进行了比较：山黄麻、日本石楠、肖蒲桃和虎舌红。在所有物种中，将在遮荫（全光照的5.3%）条件下生长的叶片转移到全光照下，导致光系统II的暗适应量子产量（Fv/Fm）在初始阶段大幅下降。先锋植物物种山黄麻的下降幅度最小（38%），而两个演替后期的植物物种肖蒲桃和虎舌红的下降幅度则很大（约80%）。在所有四个本地物种中，遮荫叶片转移后的Fv/Fm逐渐恢复，但人面子比其他物种恢复得更充分、更快。与Fv/Fm不同，所有物种的叶绿素含量在初始下降后并未恢复。这表明量子产量（Fv/Fm）的恢复与叶绿素的减少无关。在所有物种中，人面子在转移后（1）遮荫叶片的最大光合速率增加幅度最大，（2）新形成的阳生叶产量最高，（3）相对生长速率增加幅度最大。人面子在模拟林冠空隙中的生理生态特征表明，现有遮荫叶片通过最大限度地减少光抑制实现了快速光合适应，并迅速部署了具有高光合能力的新阳生叶。由于其在这些太平洋岛屿上的栖息地容易受到台风干扰，人面子的成功入侵可能在于其适应潜力与频繁的林冠空隙事件相契合。
