Seeing the forest with the leaves - clues to canopy placement from leaf fossil size and venation characteristics
Seeing the forest with the leaves - clues to canopy placement from leaf fossil size and venation characteristics
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DOI：
10.1111/j.1472-4669.2008.00176.x
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发表时间：
2009-03-01
期刊：
影响因子：
3.7
通讯作者：
Boyce, C. K.
中科院分区：
文献类型：
--
作者：
Boyce, C. K.
虽然各种各样的叶特征出现在发展过程中的光环境诱导，在生活阔叶树的个体发育变化的分析表明，一些其他性状也集中到经典的“太阳”与“阴影”的形态区别，包括叶的大小，形状和静脉密度，而不是主要由当地的液压环境内的树冠控制。这些特征随树冠位置变化的规律性为解决一个经典的古植物学难题提供了一种方法：植物源植物的高度--从草本植物或灌木到树冠树--通常不为叶化石所知。银杏在这里的研究补充了以前的工作栎，表明整个冠的叶子是相同的大小和脉序在萌芽的时候，并在很大程度上发生的形态适应当地微环境的扩张阶段后，确定的血管结构是完整的。因此，静脉密度的变化并不反映差异静脉生产，那么多的变形，类似的静脉网络在不同的最终表面积驱动的变化，在当地的液压供应在扩张过程中。与被子植物栎属的扩散生长的叶不同，银杏的边缘生长的叶确实显示出一些差异脉产生的潜力，但扩张效应仍然占主导地位。这里建议的方法可能被证明是有用的评估的可能性，两个不同的化石形态种实际上代表同一植物的叶子，并收集有关冠层结构的信息，从脱节的叶子。
Although a variety of leaf characteristics appear to be induced by light environment during development, analysis of ontogenetic changes in living broad leaved trees has suggested that a number of other traits also lumped into the classic 'sun' versus 'shade' morphological distinctions, including leaf size, shape, and vein density, are instead controlled largely by local hydraulic environment within the tree canopy. The regularity in how these traits vary with canopy placement suggests a method for addressing a classic paleobotanical quandary: the stature of the source plant - from herb or shrub to canopy tree - is typically unknown for leaf fossils. The study of Ginkgo here complements previous work on Quercus that indicated that leaves throughout the crown are identical in size and venation at the time of bud break and that morphological adaptation to the local microenvironment takes place largely during the expansion phase after the determination of the vascular architecture is complete. Hence, variation in vein density does not reflect differential vein production so much as the distortion of similar vein networks over different final surface areas driven by variation in local hydraulic supply during expansion. Unlike the diffusely growing leaves of the angiosperm, Quercus, the marginally growing leaves of Ginkgo do show some potential for differential vein production, but expansion effects still dominate. The approach suggested here may prove useful for assessing the likelihood that two distinct fossil morphospecies actually represent leaves of the same plant and to gather information concerning canopy structure from disarticulated leaves.