Development of the gametophytes, flower, and floral vasculature in Dichorisandra  thyrsiflora (Commelinaceae)

Abstract

The flowers of Dichorisandra thyrsiflora (Commelinaceae) are monosymmetric and composed of three sepals, three petals, six stamens, and three connate carpels. The anthers are poricidal and possess a wall of five cell layers (tapetum included). This type of anther wall, not previously observed in the Commelinaceae, is developmentally derived from the monocotyledonous type via an additional periclinal division and the persistence of the middle layers through anther dehiscence. Secondary endothecial thickenings develop in the cells of the two middle layers only. The tapetum is periplasmodial and contains raphides. Microsporogenesis is successive and yields both decussate and isobilateral tetrads. Pollen is shed as single binucleate grains. The gynoecium is differentiated into a globose ovary, hollow elongate style, and trilobed papillate stigma. Each locule contains six to eight hemianatropous to slightly campylotropous crassinucellar ovules with axile (submarginal) placentation. The ovules are bitegmic with a slightly zig-zag micropyle. Megagametophyte development is of the Polygonum type. The mature megagametophyte consists of an egg apparatus and fusion nucleus; the antipodals having degenerated. The floral vasculature is organized into an outer and inner system of bundles in the pedicel. The outer system becomes ventral carpellary bundles. All other floral vascular traces originate from the inner system.

Stamen morphoanatomy of Dyckia Schult.f. (Bromeliaceae, Pitcairnioideae) species: new data for taxonomic use

“…The structure of the middle layer in the mature anther proved to be of interest in the comparison among the species since, by remaining in the anthers, its cells also developed fibrous thickenings. The permanence of the middle layer with thickenings in the mature anter is common and has been reported in other monocot families, such as Rapateaceae (Oriani & Scatena 2013) and Commelinaceae (Hardy et al 2000), despite being unidentified in Dyckia and other Bromeliaceae. It probably aids in anther dehiscence together with the endothecium, due to the presence of fibrous thickening.…”

Comparative Structure and Pollen Production of the Stamens and Pollinator-deceptive Staminodes of Commelina coelestis and C. dianthifolia (Commelinaceae)

“…Raphide crystals of calcium oxalate, originating in the plasmodium, have been observed in other species of Commelinaceae (Hardy et al, 2000). Raphides in the anther may be involved in tissue degradation at the stomium to hasten anther dehiscence (Horner and Wagner, 1992), may enhance pollination by providing needed calcium for pollen germination and the elongation of the generative cell (D'Arcy et al, 1996;Iwano et al, 2004), or may form to sequester excess calcium in older anthers (Iwano et al, 2004), playing a regulatory role in the maintenance of ionic equilibrium (Dickison, 2000).…”

Morphological evolution in the graminid clade: comparative floral anatomy of the grass relatives Flagellariaceae and Joinvilleaceae

“…Eugeissona : Bobrov et al ., ). Supernumerary carpel bundles, probably correlated with relative large ovary size, are also reported in some genera of Commelinaceae (reviewed by Hardy, Stevenson & Kiss, ). However, this correlation is by no means universal.…”