Sutter Doris Merino, Endress Peter K
Institute of Systematic Botany, University of Zurich, Zollikerstrasse 107, CH-8008, Switzerland.
Ann Bot. 2003 Sep;92(3):459-69. doi: 10.1093/aob/mcg158.
The Balanopaceae, whose flowers were poorly known, have, in the past, been variously allocated to the Fagales, Euphorbiaceae, Salicales or other hamamelids and rosids (these groups being in Fagales, Malpighiales and Saxifragales, according to the Angiosperm Phylogeny Group). This paper attempts a clarification based on flower morphology. Female flowers and cupules were studied in Balanops vieillardii, young fruits in B. australiana. The cupules are simple involucres of bracts which are spirally arranged (according to a Fibonacci pattern) on the floral axis preceding the flower. They contrast with the complicated cupules of Fagaceae which consist of a condensed cymose ramification system of axes of several orders around the flower. Flowers appear later than most of the cupular bracts, in contrast to Fagaceae. In addition to a terminal flower there may be several smaller lateral flowers in the axil of cupular bracts, each surrounded by its own small cupule. The female flowers do not have a perianth. They consist of two to three large carpels. At anthesis, the ovary is completely septate; the syncarpous part (ovary and lower style) is completely symplicate. The carpels are free for most of their length, with the free parts once, twice or three times bifurcate, in contrast to simple in Fagales. The stigmatic surface covers the ventral side of each stigmatic branch and at the margins also spreads to the dorsal side. The stigma is wet and secretion appears holocrine. The two ovules per carpel are collateral and axile in early development. However, at anthesis they appear one above the other, because in one ovule the funicle greatly elongates. As the ovary elongates only above the placenta, the ovules appear basal at anthesis. The ovules are (weakly) crassinucellar, bitegmic (not unitegmic), anatropous, and intermediate between apotropous and epitropous (not apotropous). The ovules are mature at anthesis, in contrast to Fagales. In mature ovules the upper part of the nucellus disintegrates, and a weakly differentiated endothelium is present in the inner integument. The morphological results of this study support a position of Balanopaceae in Malpighiales, and not Fagales or other orders, and are thus in accordance with recent molecular results based on chloroplast rbcL sequences data. However, within Malpighiales, as opposed to molecular results, Balanopaceae agree more with Euphorbiaceae s.l. than with Dichapetalaceae/Trigoniaceae and Chrysobalanaceae/Euphroniaceae.
过去，对山毛榉科（Balanopaceae）花朵的了解甚少，该科植物曾被不同地归类于壳斗目（Fagales）、大戟科（Euphorbiaceae）、杨柳目（Salicales）或其他金缕梅类和蔷薇类植物（根据被子植物系统发育组的分类，这些类群分别属于壳斗目、金虎尾目和虎耳草目）。本文试图基于花的形态进行澄清。对维氏山毛榉（Balanops vieillardii）的雌花和壳斗进行了研究，对澳洲山毛榉（B. australiana）的幼果进行了研究。壳斗是苞片的简单总苞，这些苞片在花前方的花轴上呈螺旋状排列（按照斐波那契模式）。它们与壳斗科复杂的壳斗形成对比，壳斗科的壳斗由围绕花的几个级次的轴的密集聚伞状分枝系统组成。与壳斗科不同，花比大多数壳斗苞片出现得晚。除了顶生花外，在壳斗苞片的腋部可能还有几朵较小的侧花，每朵花都被其自己的小壳斗包围。雌花没有花被。它们由两到三个大心皮组成。开花时，子房完全分隔；合生部分（子房和下部花柱）完全对折。心皮在其大部分长度上是分离的，分离部分一次、两次或三次二叉分枝，这与壳斗目的心皮简单不同。柱头表面覆盖每个柱头分支的腹侧，在边缘也延伸到背侧。柱头湿润，分泌物为全泌型。每个心皮的两个胚珠在早期发育时是并列且轴生的。然而，开花时它们看起来一个在另一个之上，因为其中一个胚珠的珠柄大大伸长。由于子房仅在胎座上方伸长，开花时胚珠看起来是基生的。胚珠是（弱）厚珠心、双珠被（而非单珠被）、倒生，且介于离生和弯生之间（非离生）。与壳斗目不同，胚珠在开花时成熟。在成熟胚珠中，珠心的上部解体，内珠被中存在弱分化的珠被绒毡层。本研究的形态学结果支持山毛榉科在金虎尾目中的地位，而非壳斗目或其他目，因此与基于叶绿体rbcL序列数据的最新分子结果一致。然而，在金虎尾目中，与分子结果相反，山毛榉科与广义大戟科的一致性比与毒鼠子科/三角果科以及可可李科/番金莲科的一致性更高。
