A contribution to the ultrastructural knowledge of the pollen exine in subtribe Inulinae (Inuleae, Asteraceae)

Abstract

Abstract. To better understand the relationships within the Asteroideae and Inuleae, the structure of the pollen exine was investigated in seven genera and nine species of the subtribe Inulinae using LM, TEM and SEM. All taxa have a senecioid pattern of exine. The tectal complex consists of three main layers that differ in thickness and morphology: a tectum, a columellar layer, and a layer consisting of the basal region of the columellae. The absence or the vestigial condition of the foramina is considered as a plesiomorphy within the Asteroideae. All taxa have a complex apertural system that consists of an ecto-, a meso-, and an endoaperture. These apertures intersect respectively the tectal complex, the foot layer and the upper part of the endexine, and the inner layer of the endexine. A continuous transition among the different species of Inulinae was found for all the quantitative characters examined. This relative homogeneity of the pollen morphological characters enhances the naturality of the subtribe Inulinae.

A contribution to the knowledge of exine ultrastructure in subtribeAnisopappinae(Athroismeae, Asteraceae)

“…In fact, as it happened with other taxonomic groups of Asteraceae (e.g. Pereira Coutinho & Paiva 2003;Pereira Coutinho & Dinis 2007, 2009Pereira Coutinho & al. 2011), the existence of a mesoaperture intersecting the foot layer and the upper part of the endexine was well established.…”

“…1998), since the ultrastructural pattern of the exine of this last tribe is, always, Senecioid (Skvarla & al. 1977;Pereira Coutinho & Dinis 2007). The sub-Gnaphalioid pattern described by Skvarla & al.…”

A contribution to the knowledge of the exine, with special reference to the ultrastructure, in subtribe Ecliptinae (Heliantheae, Asteraceae)

“…It is our conviction that the morphology and the dimensions of the internal foramina represent two potentially useful taxonomic characters, if not in an absolute way, at least as well defined trends. In fact, the observation of the figures published in our previous works reveals that the Gaillardiinae, Galinsoginae, Gnaphaliinae and Anisopappinae exines, respectively, and consistently present elliptic (with low eccentricity) to circular (Pereira Coutinho 2002), circular or sub-circular (Pereira Coutinho and Paiva 2003), very elongated (Pereira Coutinho and Dinis 2009) and elongated (Pereira Coutinho et al 2014) internal foramina. In this work, a measurement taking of these structures was, for the first time, tried.…”

“…Skvarla and Turner (1966) and Skvarla et al (1977) considered mainly the potential taxonomic interest of the ratio endexine/foot layer, but, in our opinion, this last exine layer is relevant by itself, mostly considering its upper surface morphology. A few examples will illustrate this: the Ambrosiinae and Inulinae foot layer is quite smooth (Pereira Coutinho 2002;Pereira Coutinho andDinis 2007, Pereira Coutinho et al 2011), but the same layer assumes a much more rough morphology in the Gnaphaliinae (Pereira Coutinho and Dinis 2009). In the Ecliptinae, the upper surface of this layer varies between the smooth and the slightly rough conditions.…”

Pollen morphology in tribe Dicomeae Panero and Funk (Asteraceae)

“…Pollen grains of Erythrocephalum longifolium and Pleiotaxis rugosa were fixed in osmium tetroxide and embedded in Spurr's resin as described elsewhere (Pereira Coutinho and Dinis 2007). Thin sections were cut with an LKB Ultrotome Nova ultramicrotome equipped with a diamond knife, conventionally stained with uranyl acetate and lead citrate, and observed with a Jeol JEM-100 SX at 80 kV.…”