A histological study of microsporogenesis inTarenna gracilipes(Rubiaceae)

Abstract

We studied the microsporogenesis in Tarenna gracilipes (Hayata) Ohwi, with special attention to the mode of exine deposition and tapetum development. We based this research on light (LM), scanning electron (SEM) and transmission electron microscopic (TEM) observations of developing anthers of T. gracilipes, from the microspore mother cell stage towards anther dehiscence. Evidence is supplied that the microsporogenesis in T. gracilipes can be considered as simultaneous. Columellae, foot layer and tectum develop in a fibrillar matrix. Similar with earlier studies in Rubiaceae species, a single white line formed near the plasmalemma in the extra-apertural region. The developing endexine dilated into several white line centered lamellae at the apertures. An annulus is formed around the inner surface of each pore. In the mature intine two strata can be distinguished. At the apertures thick onci are formed protruding through the apertures thereby forming papillae, a common feature in Rubiaceae. In Rubiaceae species amoeboid as well as secretory tapeta are reported. In T. gracilipes it is shown that the tapetum cells possess in all developmental stages characteristics of the secretory type. During microsporogenesis the tapetum cytoplasm undergoes considerable changes which may indicate cycles of hyperactivity. Sporopollenin deposition on the pre-orbicules is mediated by white lines showing correlations with endexine, annulus and columellae ontogeny. These findings corroborate the idea that orbicule wall development can represent a model to study sporopollenin deposition. At anther dehiscence Ca-oxalate crystals are released out of the ruptured septum cells into the locule, providing a possible visual signal for pollinators.

Ultrastructure of microsporogenesis and microgametogenesis in Brachypodium distachyon

“…In Poaceae (Marquez et al 1997a, b) and Euphorbiaceae (Suarez-Cervera et al 2001), three layers of intine have been reported. However, in some species, such as Nelumbo lutea (Kreunen and Osborn 1999), Hypecoum imberbe (Romero et al 2003) and Tarenna gracilipes (Vinckier and Smets 2005), two strata have been reported. Furthermore, a single homogenous stratum has been described in Olea europaea (Fernandez and Rodriguez-Garcia 1988) and Lycopersicon esculentum (Fernandez et al 1992).…”

Pollen morphology supports the transfer of Wendlandia (Rubiaceae) out of Rondeletieae

“…The endoaperture is mainly an endocolpus in this clade; just as in Wendlandia , the costa is present in many previously studied species of this clade, e.g. Tarenna gracilipes (Hayata) Ohwi (Vinckier & Smets, 2005); the foot layer of T . gracilipes is also distinguishable in mature pollen and it is obviously thicker than the endexine; the special layer MGL is not observed in T .…”

Distribution of plastids and mitochondria during male gametophyte formation in Tinantia erecta (Jacq.) Fenzl

“…This type of chondriokinesis was also observed in Larix europea (Rodkiewicz et al 1984; Bednara and Rodkiewicz 1988), Larix decidua (Rodkiewicz and Duda 1988), Trandescantia virginica (Rodkiewicz et al 1984), and ”Vista Rainbow” orchid (Brown and Lemmon 1991). The neutral-equatorial type of chondriokinesis was also observed in the microsporogenesis with simultaneous cytokinesis in Chamaedorea karwinskiana (Suessenguth 1921), Tropaeolum peregrinum (Sugiura 1928), Ribes rubrum (Geneves 1967, 1971), Podocarpus macrophylla (Vasil and Aldrich 1970), Paeonia tenuifolia and Campanula rapanculoides (Dietrich 1973), Pteridium aquilinum (Sheffield and Bell 1979), Dryopteris borreri (Sheffield and Bell 1979; Sheffield et al 1983), Lycopersicon peruvianum (Pacini and Juniper 1984), Datura inoxa , Nicotiana tabacum and Antirrhinum majus (Dupuis et al 1988), Solanum nigrum (Bhandari and Sharma 1988), Polystichum loncitis (Bednara and Rodkiewicz 1988), “Sabine Queen” orchid (Brown and Lemmon 1991), Lilium longiflorum (Dickinson and Heslop-Harrison 1970; Tanaka 1991), Ophioglossum petiolatum (Brown and Lemmon 2001a, b), Psilotum nudum (Gabarayeva 1985; Lee 1982; Tchórzewska et al 1996; Tchórzewska and Bednara 2011), Ginkgo biloba (Wolniak 1976; Wang et al 1988; Brown and Lemmon 2005), Taranna gracilipes (Vinckier and Smets 2007), Armoracia rusticana (Winiarczyk et al 2007), and Arabidopsis thaliana (Brownfield et al 2015).…”