Scholes J D, Press M C, Zipperlen S W
Department of Animal and Plant Sciences, University of Sheffield, Sheffield, S10 2UQ, UK, , , , , , GB.
Oecologia. 1996 Dec;109(1):41-48. doi: 10.1007/s004420050056.
The light environment within tropical rain forests varies considerably both spatially and temporally, and photon flux density (PFD) is considered to be an important factor determining the growth and survival of rain forest tree seedlings. In this paper we examine the ability of four ecologically contrasting dipterocarps (Dryobalanops lanceolata, Shorea leprosula, Hopea nervosa and Vatica oblongifolia) to utilise and dissipate light energy when grown in different light environments in lowland dipterocarp rain forest in the Danum Valley Conservation Area, Sabah, East Malaysia. Specifically we report (i) photosynthetic light response curves and associated fluorescence characteristics, including quantum yield (ΦPSII) and non-photochemical quenching (qN) and (ii) the extent to which photoinhibition occurs when plants grown in either high or low light are exposed to short bursts of high PFD. When grown in low light (artificial or forest shade) all four species had low light saturated rates of photosynthesis which were achieved at low PFDs. In addition, values of ΦPSII and qN were similar over a range of measurement PFDs. D. lanceolata and S. leprosula were also grown at high PFD and showed marked differences in their responses. S. leprosula demonstrated an ability to increase its rate of photosynthesis and there was a small increase in capacity to dissipate excess light energy non-photochemically at high PFDs. Partitioning of this qN into its fast, photo-protective (qE) and slow, photoinhibitory (qI) components indicated that there was an increase in qE quenching. In contrast, although D. lanceolata survived in the high light environment, greater rates of photosynthesis were not observed and the plants showed a greater capacity to dissipate energy non-photochemically. Partitioning of qN revealed that the majority of this increase was attributable to the slower relaxing phases.
热带雨林中的光照环境在空间和时间上都有很大差异，光合光子通量密度（PFD）被认为是决定雨林树苗生长和存活的一个重要因素。在本文中，我们研究了四种生态特征不同的龙脑香科植物（披针叶龙脑香、白柳桉、多脉坡垒和长圆叶青梅）在东马来西亚沙巴州丹浓谷保护区低地龙脑香雨林不同光照环境下生长时利用和耗散光能的能力。具体来说，我们报告了（i）光合光响应曲线及相关荧光特征，包括量子产额（ΦPSII）和非光化学猝灭（qN），以及（ii）当在高光或低光下生长的植物暴露于短时间高PFD时发生光抑制的程度。当在低光（人工或森林荫蔽）条件下生长时，所有四个物种的光合光饱和速率都很低，且在低PFD时就可达到。此外，在一系列测量的PFD范围内，ΦPSII和qN的值相似。披针叶龙脑香和白柳桉也在高PFD下生长，且它们的反应存在显著差异。白柳桉表现出提高光合作用速率的能力，并且在高PFD下非光化学耗散过剩光能的能力略有增加。将该qN分为其快速的光保护（qE）和缓慢的光抑制（qI）成分表明，qE猝灭有所增加。相比之下，尽管披针叶龙脑香在高光环境中存活下来，但未观察到更高的光合作用速率，并且这些植物表现出更强的非光化学能量耗散能力。qN的划分显示，这种增加的大部分归因于较慢的弛豫阶段。
