The Bases of Angiosperm Phylogeny: Embryology

Abstract

Many of the embryological characteristics that may be useful, when employed judiciously and in conjunction with other characters, in arriving at taxonomic conclusions are listed Several characteristics that show a non-random distribution between families of the Magnoliatae and Aose of the Ljhatae are discussed Features which are more predominant in the monocotyledons than dicotyledons are: monocotyledonous type of development of the anther wall;^oebo?d tapetum; successive cytokinesis of the microspore mother cells to form isobilate al teTraoV helobial endosperm development; and a single cotyledon in the mature embryo. In contrast' those characteristics that are more prevalent among dicot families than monocot families include basic and dicotyledonous patterns of anther wall formation; simultaneous cytokinesis of ^0! spore mother cells with the formation of tetrahedral tetrads; hemitropous, ampin ropous or circmotropous ovules; ovules with a single integument; an endotheliuni; OeJhera PeLa Peperorma Plumbago or Plumbagella types of megagametophyte development; cellulaf eX S^tW °°*l S m ^ matUre embrya In Spite ° f these differenced those characteristics that are most common-occurring in at least 70%, and usually more, of all angiosperms -are evenly distributed between the two classes and afford a strong embryological unity foX angiosperms. These widespread characters include: four microsporia per lither^feLti! ated endothelium; two-celled pollen grains; bitegmic anatropous ovules" Polygonum t£>e of megagametophyte development; and nuclear endosperm. Within the two classes distributon of £ exlZV r 1Sn °l ^^ ?, r0 P° rtional am ^S tibe several subclasses and superb for example a unitegmic, tenumucellate ovule with an endothelium, cellular endosperm with haustona and Solanad embryogeny predominates in the Ericanae and Asteridae; or helob al J± S™ ^ a d t St ir tlVe ^^ °f *? A^dae. On the whole, embryological characteristics are remarkably constant at the family level. In those families where variation does occur, genera are usually constant, although a few notable examples of mtragenerS and even T3&XT? d ° 6XiSt ' " 1°J eXam ^V n PattemS ° f -gagametophyte dLTopment cateeorie^ofSrl ^T™? usef ^ess of the grosser aspects of embryology-the major de afk wtthl I ^ or f devel °P m e nt -^me evidence is presented suggesting that variation in nSZ^T^ g cate f or y> such as size > shape, and cellular characteristics of the developing SnerT ^ megagamet0phyte ' may be helpfuI fa det emiining relationships within famUies, gcucid, or species.

Perspective: The Origin of Flowering Plants and Their Reproductive Biology?a Tale of Two Phylogenies

“…Whereas upper cells derived from the embryo tier or the embryonal mass contribute to the secondary suspensor in other seed plants, the primary suspensor cell of angiosperms usually contributes to the radicle of the embryo as well as the suspensor. An exception, the caryophyllad type, is restricted to some monocots and eudicots such as Caryophyllaceae and Saxifragales (Maheshwari 1950, Palser 1975, Sporne 1974) and can therefore be interpreted as derived. In Doyle (1996), I expressed these differences in terms of two characters, lack of tiers and lack of a secondary suspensor.…”

Modularity of the Angiosperm Female Gametophyte and Its Bearing on the Early Evolution of Endosperm in Flowering Plants

“…Among angiosperms, monosporic seven-celled/eight-nucleate female gametophytes have been almost universally viewed as ancestral (Palser 1975;Haig 1990;see Rajan 1976 for an exception). Thus, the common, and presumably Polygonum-type female gametophyte has served as the standard against which to compare variant female gametophyte types.…”

“…The monosporic seven-celled/eight-nucleate Polygonumtype female gametophyte has long served as a focal point for discussion of the origin and subsequent evolution of the angiosperm female gametophyte (Schnarf 1931;Maheshwari 1950;Johri 1963;Davis 1966;Foster and Gifford 1974;Stebbins 1974;Palser 1975;Takhtajan 1976;Favre-DuChartre 1984;Cronquist 1988;Battaglia 1989;Haig 1990;Donoghue and Scheiner 1992;Tobe et al 2000). All other female gametophyte ''types'' have been described as arising through modification of an ancestral ontogeny typical of the Polygonum type (Palser 1975;Battaglia 1989).…”

“…All other female gametophyte ''types'' have been described as arising through modification of an ancestral ontogeny typical of the Polygonum type (Palser 1975;Battaglia 1989). The documentation of a monosporic four-celled/four-nucleate female gametophyte in Nuphar, as well as its inferred presence in many of the other earliest lineages of angiosperms, suggests, for the first time, alternative interpretations of female gametophyte developmental evolution.…”

Embryology of Ageratum conyzoides L. and A. fastigiatum R.M. King & H. Rob. (Asteraceae)

“…Embryological data are constant for genera, making may be useful in determining taxonomic relationships within families, genera, or species (Palser 1975;Stuessy 2009). Thus, this study aims to investigate the embryology of A. conyzoides and A. fastigiatum, thereby testing the phylogenetic hypothesis of Hattori (2013) with an ontogenetic approach.…”