Floral development of Alisma triviale

Abstract

The primordia of the floral appendages are initiated in acropetal order. They develop in the same order in which they appear but for the petals, which are retarded in their early growth and mature rapidly shortly before anthesis. While the sepal primordia are dorsiventral from their inception, the primordia of other appendages are of nearly radial symmetry and become more or less dorsiventral in their later stages of development. Each petal primordium together with the primordia of a stamen pair arise on one common petal–stamen (CA) primordium. The many pistil primordia arise on three antesepalous gynoecial bulges and the area between them. Thus, in its development the flower exhibits primarily a tricyclic trimerous plan. The floral apices have a two-layered tunica up to the stage of pistil inception. The initiation of all floral appendages occurs by periclinal divisions in the second layer. The third layer (corpus) may contribute, especially in the case of the petal–stamen primordia and the gynoecial bulges. The development of procambium is acropetal. Each primordium receives a single procambial strand shortly after its initiation. Thus, procambial differentiation occurs as a response to primordial inception and not according to the principle of the conservatism of vascular tissue. Additional procambial strands may differentiate as a response to increase in size. The relationships of Alisma to some ranalian families are discussed. Since the floral pattern of Alisma may be considered as a secondary derivation from a trimerous pattern, it does not appear primitive at all. Other primitive features such as apocarpy and lack of fusion of pistil margins are however retained. Thus, Alisma is a good example for heterobathmy.

Flower structure and development of Araceae compared with alismatids and Acoraceae

“…In Potamogeton associated tepal and stamen additionally share a pronounced common base, which is not found in Acorns, Juncaginaceae or most Araceae. Nevertheless, in all these taxa stamens and tepals develop from clearly distinct whorls, and not from common primordia (Araceae, Eyde et al, 1967;Barabe et al, 1987;Barabe, 1994;Poisson, 1996;Poisson & Barabe, 1998;this study;Potamogeton and Triglochin, Hill, 1900;Singh & Sattler, 1972;Sattler, 1973;Posluszny & Sattler, 1974a,b;Lieu, 1979;Tomlinson, 1982;Acorus, Sattler, 1973;Buzgo & Endress, 2000;some Alismataceae, Charlton, 199913). Exceptions are Symplocarpus and Lysichiton (Orontioideae), where tepal and stamen of the same sector are formed from a common primordium, similar to some alismatids (Lumnium and Wiesneria, Alismataceae) (Singh & Sattler, 1972, 1974, 1977aBurger, 1977;Lieu, 1979;Charlton, 1981;Tomlinson, 1982;Charlton, 1999a).…”

“…In most alismatids the carpels do not form an adaxial querzone (Troll, 1931;Eber, 1934;Singh & Sattler, 1972, 1977aTomlinson, 1982; but see Charlton, 1999a,b). This results in perfectly plicate carpels (Troll, 1931;Eber, 1934).…”

“…In some alismatids a proliferation of the apex leads t o the addition of one or several carpel whorls, such as in Sagittaria cuneata, Alisma triuiale, A. lanceolata, Lumnium natans (Alismataceae), Limnocharis (Limnocharitaceae), Butomus (Butomaceae), Potamogeton lucens (Potamogetonaceae), and Triglochin maritimum and Triglochin sect. Pmceruin (Juncaginaceae) (Hill, 1900;Troll, 1931;Eber, 1934;Singh & Sattler, 1972, 1974, 1977aCharlton, 1999a). In taxa with smaller flowers the floral apex may elongate and result in a residuum in the centre of the gynoecium, such as in Aponogetonaceae, some Juncaginaceae, some Alismataceae and some Potamogetonaceae (Eber, 1934;Singh (& Sattler, 197713;Charlton, 1999a;pers.…”

“…In Butomaceae, Alismataceae, Limnocharitaceae, Hydrocharitaceae (Eber, 1934;Singh & Sattler, 1972;Tomlinson, 1982;Dahlgren et al, 1985;Haynes et al, 1998a) and in Scheuchzeria (Haynes et al, 1998e;Tomlinson, 1982) the ovules are anatropous. In Aponogetonaceae the ovules vary from anatropous to campylotropous (Dahlgren et al, 1985).…”

“…However, ovule structure varies within families (Aponogetonaceae, Juncaginaceae, Potamogetonaceae), and orthotropy may or may not be the symplesiomorphic state for basal monocots (Engler, 1905(Engler, , 1911(Engler, , 1920aEngler & Krause, 1908;Dahlgren et al, 1985;French, 1986;Grayum, 1990Grayum, , 1991Mayo et al, 1997Mayo et al, , 1998. In alismatids ovules are generally bitegmic (Singh & Sattler, 1972;Dahlgren et al, 1985). In Acorus micropylar papillae (fimbriate structures) were found on the integuments (French, 1987;Grayum, 1987Grayum, , 1991Rudall, 1997;Rudall & Furness, 1997;Buzgo & Endress, 2000).…”