Lee D W, Oberbauer Steven F, Krishnapilay Baskaran, Mansor Marzalina, Mohamad Haris, Yap Son Kheong
Department of Biological Sciences, Florida International University, Miami, FL 33199, USA and Fairchild Tropical Garden, Miami, FL 33156, USA, , , , , , US.
Forest Research Institute of Malaysia, Kuala Lumpur 52109, Malaysia, , , , , , MY.
Oecologia. 1997 Mar;110(1):1-9. doi: 10.1007/s004420050126.
Seedling developmental responses to understory shade combine the effects of reductions in irradiance and changes in spectral quality. We studied the seedling development of two Southeast Asian dipterocarp trees in response to differences in irradiance (photosynthetic photon flux density, PPFD) and spectral quality (red to far-red ratio, R:FR). The two species, Hopea helferei and H. odorata, are taxonomically closely related but differ in their ecological requirements; H. helferei is more drought-tolerant and typically grows in more open habitats. Seedlings were grown in six different replicated shadehouse treatments varying in percentage of solar PPFD and R:FR. The two species differed in the influence of light variables on most seedling characters, particularly for final height, internode distance, branch/trunk internodes, stem length/mass, leaf area/stem length, petiole length, and growth/mol of photons received. Most of the characters in both taxa were primarily influenced by PPFD, but spectral quality also influenced some characters - more so for H. odorata. The latter species grew more rapidly, particularly in the low PPFD treatments, and its leaves were capable of higher photosynthesis rates. However, growth in H. helferei was not reduced in direct sunlight. The growth of this taxon may be constrained by adaptations, particularly in leaves, for drought tolerance.
幼苗对林下遮荫的发育反应综合了光照强度降低和光谱质量变化的影响。我们研究了两种东南亚龙脑香科树木的幼苗发育，以探究光照强度（光合光子通量密度，PPFD）和光谱质量（红/远红比率，R:FR）差异的影响。这两个物种，即赫氏坡垒（Hopea helferei）和香坡垒（H. odorata），在分类学上亲缘关系密切，但生态需求不同；赫氏坡垒更耐旱，通常生长在更开阔的栖息地。幼苗在六种不同的重复遮荫棚处理中生长，这些处理在太阳PPFD百分比和R:FR方面有所不同。这两个物种在光照变量对大多数幼苗性状的影响上存在差异，特别是在最终高度、节间距离、枝/干节间、茎长/质量、叶面积/茎长、叶柄长度以及每摩尔接收光子的生长量方面。两个分类群中的大多数性状主要受PPFD影响，但光谱质量也影响了一些性状——对香坡垒的影响更大。后一个物种生长得更快，特别是在低PPFD处理中，并且其叶片能够进行更高的光合速率。然而，赫氏坡垒在直射阳光下的生长并未受到抑制。该分类群的生长可能受到适应性的限制，特别是在叶片方面，以适应耐旱性。
