Lee D W, Oberbauer S F, Johnson P, Krishnapilay B, Mansor M, Mohamad H, Yap S K
Department of Biological Sciences, Florida International University, Miami, Florida 33199 USA Fairchild Tropical Garden, Miami, Florida 33156 USA;
Am J Bot. 2000 Apr;87(4):447-55.
We studied the development of leaf characters in two Southeast Asian dipterocarp forest trees under different photosynthetic photon flux densities (PFD) and spectral qualities (red to far-red, R:FR). The two species, Hopea helferi and H. odorata, are taxonomically closely related but differ in their ecological requirements; H. helferi is more drought tolerant and H. odorata more shade tolerant. Seedlings were grown in replicated shadehouse treatments of differing PFD and R:FR. We measured or calculated (1) leaf and tissue thicknesses; (2) mesophyll parenchyma, air space, and lignified tissue volumes; (3) mesophyll air volumes (V(mes)/A(surf)) and surfaces (A(mes)/A(surf)); (4) palisade cell length and width; (5) chlorophyll/cm and a/b; (6) leaf absorption; and (7) attenuance/absorbance at 652 and 550 nm. These characters varied in response to light conditions in both taxa. Characters were predominantly affected by PFD, and R:FR slightly influenced many characters. Leaf characters of H. odorata were more plastic in response to treatment conditions. Characters were correlated with each other in a complex fashion. Variation in leaf anatomy is most likely a consequence of increasing leaf thickness in both taxa, which may increase mechanical strength and defense against herbivory in more exposed environments. Variation in leaf optical properties was most likely affected by pigment photo-bleaching in treatments of more intense PFD and was not correlated with A(max). The greater plasticity of leaf responses in H. odorata helps explain the acclimation over the range of light conditions encountered by this shade-tolerant taxon. The dense layer of scales on the leaf undersurface and other anatomical characters in H. helferi reduced gas exchange and growth in this drought-tolerant tree.
我们研究了两种东南亚龙脑香科森林树木在不同光合光子通量密度（PFD）和光谱质量（红光与远红光之比，R:FR）下叶片特征的发育情况。这两个物种，即菲律宾坡垒（Hopea helferi）和香坡垒（H. odorata），在分类学上关系密切，但生态需求不同；菲律宾坡垒更耐旱，香坡垒更耐荫。幼苗在不同PFD和R:FR的重复遮荫棚处理中生长。我们测量或计算了：（1）叶片和组织厚度；（2）叶肉薄壁组织、气腔和木质化组织体积；（3）叶肉气腔体积（V(mes)/A(surf)）和表面积（A(mes)/A(surf)）；（4）栅栏细胞长度和宽度；（5）叶绿素含量/cm以及叶绿素a/b比值；（6）叶片吸收率；以及（7）652和550nm处的衰减率/吸光度。在这两个分类群中，这些特征均随光照条件而变化。特征主要受PFD影响，R:FR对许多特征有轻微影响。香坡垒的叶片特征对处理条件的可塑性更强。各特征之间以复杂的方式相互关联。叶片解剖结构的变化很可能是由于两个分类群中叶片厚度增加所致，这可能会在更开阔的环境中增强机械强度并抵御食草动物。叶片光学特性的变化很可能受到更高PFD处理中色素光漂白的影响，且与最大光合速率（A(max)）无关。香坡垒叶片反应的更大可塑性有助于解释这个耐荫分类群在其所遇到的光照条件范围内的适应性。菲律宾坡垒叶片下表面的致密鳞片层和其他解剖特征降低了这种耐旱树木的气体交换和生长。
