馬尾樹花粉外壁構造的研究

Structure of the Pollen Exine of Rhoiptelea chiliantha

本文主要描述馬尾樹（Rhoiptelea chiliantha）成熟花粉粒的外壁構造。成熟花粉粒大小約23-27μm、三溝孔、具短溝、寬約1-2μm、長約10-12μm。馬尾樹花粉粒上的小刺（spinules）形狀與大小和一些龍膽目（Gentianales）植物的花粉粒很相似，小刺是由寬約70 nm的棒狀物所組成。這些棒狀物明顯地分佈在蓋頂層（tectum）及柱狀層（columellae）各處。柱狀層中有兩種大小不同的柱狀體，較小的寬約70 nm連接蓋頂層和較大的柱狀體，而較大的柱狀體是由多個寬70 nm的棒狀物所組成的，它們會和基層（foot layer）末端相連，而基層頂端表面有著明顯分佈的白線（white line）特徵，就好像是它與外壁內層（endexine）的接合面（junction plane）。外壁內層有兩種組成，鄰近基層的實心組成為endexine-1，另一則為片狀endexine-2，它會與外層連接進而成為其endexine-1的一部份。沒有觀察到明顯的arcus存在。在保存良好的花粉粒上可觀察到花粉孔被孔蓋或似孔蓋物所覆蓋。而水合後的花粉粒會在萌芽孔下方、內壁上方隆起許多複雜的脊狀物（oncus）。烏氏體（Ubisch bodies）上廣泛分佈著類似花粉外壁上的小刺狀裝飾物。

The exine of mature pollen grains of Rhoiptelea chiliantha was studied. The size of the pollen grains is about 23 by 27 μm. They are tricolporate with short colpi that are 1-2 μm wide and 10-12 long. The spinules of Rhoiptelea are similar in form and size to those of Gentianales. The spinules consist of rods of ca 70 nm in width. These rods are evident throughout the tectum and columellae. The columellae are of two distinct sizes. The smaller ones are ca 70 nm wide and join the tectum and the larger columellae. These larger ones appear to be composed of several 70 nm in width rods. They join the distal surface of the foot layer. The proximal surface of the foot layer is marked by a white line (referred to as a junction plane) where it joins the endexine. The endexine consists of a solid-appearing component adjacent to the foot layer (referred to as endexine-1) and laminar components (endexine-2) that are attached to and apparently become a part of endexine-1. There is no indication of an arcus. In well preserved grains the aperture is covered by an operculum or operculum-like component. In well-rehydrated pollen grains there is an oncus of considerable complexity under the aperture and over the intine. The Ubisch bodies have an exine ornamented with widely-spaced spinules like the spinules on the pollen exine.