Harvard Forest, Harvard University, 324 North Main Street, Petersham, Massachusetts 01366 USA.
Am J Bot. 2009 Oct;96(10):1787-97. doi: 10.3732/ajb.0800385. Epub 2009 Sep 17.
We present a preliminary description of the morphology and anatomy of contrasted axes in the recently discovered conifer Wollemia nobilis, based on clonally propagated material. The novelty of this discovery and the tree's size and rarity has led to global interest and a comprehensive and successful conservation program. Our results should serve as a model on which future studies of this tree and other members of the Araucariaceae can be based. The specimens studied are mimics of the architecture of the mature tree, with precise distinction between orthotropic (= trunk) axes, which have radial symmetry (spiral phyllotaxy) and plagiotropic (= branch) axes with dorsiventral symmetry (as a modified decussate phyllotaxy). Trunk axes develop irregular pseudowhorls of branches that originate within the terminal bud by syllepsis, their extension coincident with that of the parent axis. The two kinds of axes show considerable anatomical differences, but are still based on the common feature of a single stelar-derived trace to each leaf that becomes subdivided in the cortex, a feature of the whole family. Trunk axes include extended cortical leaf and branch traces associated with abundant sclerenchyma, but branches have short cortical leaf traces, no branch traces, and limited sclerenchyma. Reiteration is limited and largely involves the formation of basal suckers on the trunk. Branches normally remain unbranched, but can do so most often when damaged. This study thus emphasizes the phenomenon of axis differentiation in conifers, which has been little investigated anatomically, but could be very important in the identification of fossils.
我们根据无性繁殖材料对最近发现的松柏类植物沃尔勒姆松的对比轴的形态和解剖结构进行了初步描述。这一发现的新颖性以及树木的大小和稀有性引起了全球的关注，并制定了全面而成功的保护计划。我们的研究结果应该为未来对这种树和其他南洋杉科成员的研究提供一个模型。研究的标本模仿了成熟树的结构，具有精确的正交轴（=树干）和偏轴（=树枝）之间的区别，正交轴具有径向对称性（螺旋叶序），偏轴具有背腹对称性（作为一种改良的对生叶序）。树干轴发育出不规则的假轮生分枝，它们通过侧生分枝起源于顶芽，其延伸与母轴的延伸一致。两种轴具有相当大的解剖学差异，但仍基于每个叶子由单个中柱衍生的痕迹的共同特征，在皮质中被细分，这是整个科的特征。树干轴包括与丰富的厚壁组织相关的扩展皮质叶和分支痕迹，但分支具有短皮质叶痕迹、没有分支痕迹和有限的厚壁组织。重复是有限的，主要涉及树干上形成的基生吸根。树枝通常保持不分枝，但在受到损伤时最常分枝。因此，这项研究强调了松柏类植物轴分化的现象，这种现象在解剖学上研究较少，但在化石鉴定中可能非常重要。
