NV Tcitcin Main Botanical Garden RAS, Moscow, 127276, Russia.
Ann Bot. 2011 Dec;108(8):1489-502. doi: 10.1093/aob/mcr148. Epub 2011 Aug 10.
The Borasseae form a highly supported monophyletic clade in the Arecaceae-Coryphoideae. The fruits of Coryphoideae are small, drupaceous with specialized anatomical structure of the pericarp and berries. The large fruits of borassoid palms contain massive pyrenes, which develop from the middle zone of the mesocarp. The pericarp structure and mode of its development in Borasseae are similar to those of Eugeissona and Nypa. A developmental carpological study of borassoid palms will allow us to describe the process of pericarp development and reveal the diagnostic fruit features of borassoid palms, determine the morphogenetic fruit type in Borasseae genera, and describe similarities in fruit structure and pericarp development with other groups of palms.
The pericarp anatomy was studied during development with light microscopy based on the anatomical sections of fruits of all eight Borasseae genera.
The following general features of pericarp structure in Borasseae were revealed: (1) differentiation of the pericarp starts at early developmental stages; (2) the exocarp is represented by a specialized epidermis; (3) the mesocarp is extremely multilayered and is differentiated into several topographical zones - a peripheral parenchymatous zone(s) with scattered sclerenchymatous elements and vascular bundles, a middle zone (the stony pyrene comprising networks of elongated sclereids and vascular bundles) and an inner parenchymatous zone(s); (4) differentiation and growth of the pyrene tissue starts at early developmental stages and ends long before maturation of the seed; (5) the inner parenchymatous zone(s) of the mesocarp is dramatically compressed by the mature seed; (6) the endocarp (unspecialized epidermis) is not involved in pyrene formation; and (7) the spermoderm is multilayered in Hyphaeninae and obliterated in Lataniinae.
The fruits of Borasseae are pyrenaria of Latania-type. This type of pericarp differentiation is also found only in Eugeissona and Nypa. The fruits of other Coryphoideae dramatically differ from Borasseae by the pericarp anatomical structure and the mode of its development.
波那萨草族在棕榈科-鱼尾葵族中形成了一个高度支持的单系群。鱼尾葵族的果实很小，为核果状，具有特殊的果皮解剖结构和浆果。波那萨草族大型果实的种皮中含有大量的大孢子叶，这些大孢子叶从中果皮的中部区域发育而来。波那萨草族的果皮结构及其发育方式与 Eugeissona 和 Nypa 相似。对波那萨草族的果实进行发育性孢粉学研究，可以描述果皮发育的过程，并揭示波那萨草族果实的特征，确定波那萨草族属的形态发生果实类型，并描述与其他棕榈科组果实结构和果皮发育的相似之处。
利用基于波那萨草族所有 8 个属果实解剖切片的光学显微镜，研究果皮的解剖结构在发育过程中的变化。
揭示了波那萨草族果皮结构的以下一般特征：（1）果皮的分化始于早期发育阶段；（2）外果皮由特殊的表皮组成；（3）中果皮非常多层，分化为几个拓扑区域——一个周边的薄壁组织区（含有分散的厚壁组织和维管束）、一个中间区（石质大孢子叶包含由伸长的石细胞和维管束组成的网络）和一个内薄壁组织区（s）；（4）大孢子叶组织的分化和生长在早期发育阶段开始，并在种子成熟之前很久就结束；（5）中果皮的内薄壁组织区（s）被成熟的种子显著压缩；（6）内果皮（无特殊表皮）不参与大孢子叶的形成；（7）精子层在 Hyphaeninae 中是多层的，而在 Lataniinae 中则是消失的。
波那萨草族的果实为 Latania 型的大孢子叶球。这种果皮分化类型也仅存在于 Eugeissona 和 Nypa 中。其他鱼尾葵族的果实与波那萨草族的果实显著不同，表现在果皮的解剖结构和发育方式上。
