Comparative floral structure and systematics in Apodanthaceae (Rafflesiales)

Abstract

Comparative studies on floral morphology, anatomy, and histology were performed to identify shared features of the genera of Apodanthaceae (Rafflesiales): Apodanthes, Pilostyles, and Berlinianche. Berlinianche was studied for the first time in detail and its affinity to Apodanthaceae was confirmed. It has a previously undescribed hair cushion on the inner perianth organs and inaperturate pollen. Shared features of members of Apodanthaceae are: unisexual flowers; three (or four) alternating di-/tetra-or tri-/hexamerous whorls of scales of which the inner one or two correspond to a perianth; a synandrium with pollen sacs typically arranged in two rings; opening by a dehiscence line between the two rings of pollen sacs; large vesicular hairs above the synandrium; a gynoecium with four united carpels; inferior and unilocular ovaries with four parietal placentae, ovules tenuinucellate, anatropous with two well developed integuments, oriented in various directions; a nectary disk. Apodanthaceae share some special structural features with Malvales

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“…These data, in conjunction with the results from the mitochondrial genes, support an evolution of Apodanthaceae independent from Rafflesiaceae s. str. The well-supported relationship between Pilostyles and Apodanthes using matR is expected given their very similar floral morphology [31], yet this clade is sister to two representatives of Cucurbitales ( Begonia and Cucurbita ). Contamination with host tissue is excluded because neither parasite is known to currently occur on a member of Cucurbitales.…”

“…Morphological features shared between Apodanthaceae and Cytinaceae are: unisexual flowers, a connate androecium, an inferior ovary, and a unilocular ovary with four parietal placentae bearing numerous, anatropous, tenuinucellate ovules [30,31]. Floral morphological features that might link Apodanthaceae and Cytinaceae with Malvales [31] include an androecial tube (e.g., Malvaceae), a trend toward synandria without anthers and thecae (e.g., Malvaceae) [29], tri- to hexamerous flowers (e.g., Thymelaeaceae), and parietal placentae (e.g., Cistaceae).…”

“…Floral morphological features that might link Apodanthaceae and Cytinaceae with Malvales [31] include an androecial tube (e.g., Malvaceae), a trend toward synandria without anthers and thecae (e.g., Malvaceae) [29], tri- to hexamerous flowers (e.g., Thymelaeaceae), and parietal placentae (e.g., Cistaceae). The floral conditions of unisexuality and epigyny do occur in Malvales, albeit rarely.…”

Diversity and Lability of Floral Phyllotaxis in the Pluricarpellate Families of Core Laurales (Gomortegaceae, Atherospermataceae, Siparunaceae, Monimiaceae)

“…Double or multiple positions also occur in other basal angiosperms (e.g., Nymphaeales [Endress 2001], Annonaceae [Endress 1987;Leins and Erbar 1996], and Aristolochiaceae [Leins and Erbar 1985]) and in basal eudicots, although double positions have not always been noticed as such in the older literature (e.g., Papaveraceae [Murbeck 1912], Ranunculaceae [Schö ffel 1932]). Double or multiple positions most commonly occur at the transition from the perianth to the androecium, associated with a decrease in organ size (as in Annonaceae [Leins and Erbar 1996] or as in a number of eudicots [reviewed in Endress 1987[reviewed in Endress , 1994Smets 1993a, 1993b]), but they may also occur earlier, within the perianth (Endress 1994(Endress , 2001Blarer et al 2004; this study), or later, within the androecium or at the onset of the gynoecium (this study). The term ''dédoublement'' was used by earlier authors (e.g., de Candolle 1813) to imply the splitting of a primordium into two.…”

Structure of staminate flowers, microsporogenesis, and microgametogenesis in <em>Helosis cayennensis</em> var. <em>cayennensis</em> (Balanophoraceae)

“…This reduction is a character common in par- asitic plants, for example Korthalsella possess reduced flowers (Viscaceae, Huaxing & Gilbert, 2003), or in Balanophora, Langsdorffia, Thonningia and Rhopalocnemis genera (Balanophoraceae, Kuijt, 1969;Eberwein & al., 2009). In Apodanthaceae, the anthers form a tube that surrounds the sterile gynoecium, in which neither thecae nor stamens can be recognized, pollen sacs are arranged in pairs, and the dehiscence is produced by a transverse aperture through the two rings of the pollen sacs (Blarer & al., 2004).…”