Stamen development in the Ericaceae. I. Anther wall, microsporogenesis, inversion, and appendages

Abstract

Development of the introrse, tetrasporangiate, and normally dorsifixed and poricidal stamens has been studied at the gross morphological and cellular level in ten species of Ericaceae. Microsporogenesis, followed in four species, is normal, with cytokinesis simultaneous, forming tetrahedral tetrads. The tricolp(or)ate pollen is shed as permanent tetrads with each segment two-celled except in Enkianthus in which pollen grains are three-celled monads. Anther-wall development is similar in all four species initially, but no regular pattern of wall development could be recognized thereafter. The tapetum, of parietal origin, is binucleate, glandular, and mainly uniseriate. Viscin threads occur with the tetrads in the three rhododendroid species. A well-developed endothecium appears only in Enkianthus.Soon after stamen initiation, anthers of nine species invert at the eventual filament-anther junction to become introrse; in Enkianthus inversion occurs close to anthesis. Microsporogenesis starts during early inversion; greater cell elongation on the abaxial side of the young anther completes inversion by the late sporogenous-tissue stage. In Erica and, to a lesser extent Calluna, inversion results from greater abaxial than adaxial increase in cell number and length just above the filament-anther junction. The single vascular strand reflects the degree of inversion. Stamens of six species are appendaged; three have only awns, two only spurs, while one has both. Appendages arise from residual meristems after inversion is completed (or almost so) in all except Enkianthus. Awns develop at what will be the apex at maturity of each anther half. Their length and orientation vary among species. Only in Vaccinium do the awns become hollow (tubules). Spurs, varying in length, shape, and size, arise on the abaxial side from the filament, connective, or thecae.

Pollen functional ability in two indigenous grapevine cultivars in Bosnia and Herzegovina

“…An ultrastructural study of the microsporogenous tissue of other plants, from premeiotic stages to anthesis, were reported recently (Polowick & Sawhney, 1993;ElGhazaly & Rowley, 1999;Hermann & Palser, 2000;Suzuki et al, 2001;Teıxeıra et al, 2002).…”

Three new species of Disterigma (Ericaceae: Vaccinieae) from Western Colombia, with comments on morphological terminology

“…ex J. St.-Hil. (Smith, 1943;Palser, 1961;Luteyn, 1996;Hermann & Palser, 2000;Luteyn & Wilbur, 2005). It is important to note that the basal appendage is not equivalent to prognathous anthers, as defined by Hermann and Palser (2000).…”

“…They are called awns when they are bristle-like and sit above the dehiscence aperture, and are called tubules when they are hollow extensions of the thecae that bear the aperture distally, through which pollen is shed. Awns can be single or bifurcate, whereas tubules are one per theca but can fuse laterally to become one per anther with its cavity double, lobed, or single (Palser, 1961;Hermann & Palser, 2000). On the other hand, spurs arise on the abaxial (dorsal) side of the stamen either from the apex of the filament, the connective, and/ or from the adjacent area of the thecae.…”

“…Palser (1961) and Hermann and Palser (2000) distinguished two principal types of appendages in Ericaceae, awns and spurs, based on either developmental or morphological studies from representatives of a variety of lineages (Rhododendron L., Kalmia L., Elliottia Muhl. ex Elliott, Erica L., Calluna Salisb., Enkianthus Lour., Pieris D.…”

Biologia floral e visitantes de Gaylussacia brasiliensis (Spr.) Meissner (Ericaceae) - uma espécie com anteras poricidas polinizada por beija-flores

“…Este tipo de síndrome é associado a algumas famílias de plantas, tais como Solanaceae e Melastomataceae (Buchman 1983;Bezerra & Machado 2003;Fenster et al 2004). A família Ericaceae comumente apresenta fl ores com anteras poricidas (Hermann & Palser 2000) e polinização por abelhas, mas vários grupos tropicais da família apresentam polinização por beija-fl ores (Luteyn 2002;2004;Navarro et al 2008). Esta família possui distribuição cosmopolita, sendo encontrada em quase todas as partes do mundo e apresenta cerca de 125 gêneros, com aproximadamente 4500 espécies (Kron et al 2002;Luteyn 2002).…”