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

Abstract

We analyzed the microgametogenesis and microsporogenesis of the male flowers of the holoparasitic Helosis cayennensis (Sw.) Spreng. var. cayennensis using optical and scanning electron microscopy. The unisexual flowers are embedded in a dense mass of uniseriate trichomes (filariae). Male flowers have a tubular 3-lobed perianth, with bilayered and non vascularized tepals. The androecium consists of three stamens with filaments and thecae connated into a synandrium. It has adnate a free central pistillode without megagametophyte. Staminal filaments, fused at their base to the perianth tube and distally free along a short section, have a single vascular bundle. The distal portion of the synandrium is formed by nine pollen sacs: six outer sacs are located laterally to each filament and three longer inner sacs. The anther wall consists of the epidermis, two parietal layers (that collapse at anther maturity), and an uninucleate secretory tapetum. There is no endothecium. During microsporogenesis, the stem cells produce tetrads of microspores by meiosis. The cytokinesis is simultaneous, forming tetrahedrally arranged tetrads. When pollen grains are in the tricellular state, the synandrium emerges from the mass of filariae, and anthers dehiscence occurs apically through longitudinal slits. In conclusion, despite the extreme reduction of flowers, the anatomic characteristics and gametophyte development of staminate flowers of H. cayennensis are perfectly normal and functional. They are thus highly similar to other genera of the holoparasitic subfamily Helosidoideae. Sterile parts of flowers and inflorescence maintain the same distinctive and aberrant features of the plant vegetative parts.

Embryology in Helosis cayennensis (Balanophoraceae): Structure of Female Flowers, Fruit, Endosperm and Embryo

“…The present study focuses on H. cayennensis , as part of a broader project lead by the first author on the embryology of traditionally circumscribed Balanophoraceae (hereafter referred to as Balanophoraceae s.l.) [12,13,14,15,16]. The species was found in 2006 ([17] fontana), growing in a single spot of about 15 m 2 in a mesophyll forest of Argentina, where the only evidence of its presence was the appearance of numerous inflorescences at various developmental stages, from barely visible buds hidden in the forest mulch to open mature inflorescences.…”

“…The highly modified underground vegetative body of H. cayennensis is composed of tubers and rhizome-likes branches lacking buds or leaves [2,3,18]. In this monoecious species, 5–10 cm long spadix-like inflorescences emerge in a short period of time, are covered with peltate hexagonal scales when young and unisexual flowers are embedded in a dense layer of filariae [2,4,12,19]. Male and female flowers are clustered, located around each scale of the inflorescence, which acts as a hermaphrodite blossom [1,12].…”

“…In this monoecious species, 5–10 cm long spadix-like inflorescences emerge in a short period of time, are covered with peltate hexagonal scales when young and unisexual flowers are embedded in a dense layer of filariae [2,4,12,19]. Male and female flowers are clustered, located around each scale of the inflorescence, which acts as a hermaphrodite blossom [1,12]. Gonzalez et al [12] described the development and structure of the staminate flowers, including pollen formation and the anatomical structure of the inflorescence, whereas female flowers remained unstudied.…”

“…Male and female flowers are clustered, located around each scale of the inflorescence, which acts as a hermaphrodite blossom [1,12]. Gonzalez et al [12] described the development and structure of the staminate flowers, including pollen formation and the anatomical structure of the inflorescence, whereas female flowers remained unstudied.…”

A New Caribbean Species of <I>Helosis</I> (Balanophoraceae) with a Revised Key to the Genus

“…The reproductive structure of Helosis consists of a spadixlike inflorescence (inflorescence head), bisexual, lacking the spathe typical of a true spadix (González et al 2013). The inflorescence stalk, which bears the inflorescence head, can be short ( 1 cm) or long (up to 50 cm), and is devoid of scaly leaves, usually exhibiting a vestigial tuber tissue known as the volva.…”