Ovular development and morphology in some magnoliaceae species

2001

American J of Botany

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Ovule and seed development in six species of Nymphaeales was examined. In the Cabombaceae the two species studied resemble some extant basal angiosperms by having a hood-shaped outer integument. A micropyle-hilum complex results when the outer integument and derived testa are lacking between the micropyle and the funiculus, thus the hood-shaped appearance. In the Nymphaeaceae the outer integument is annular at an early stage and then cup-shaped though it is semiannular at initiation in Nupar japonicum and Nymphaea alba. The micropyle and hilum are separated by an intervening testa. Developmental data on the formation of the outer integument, from semiannular to hood-shaped vs. from annular to cup-shaped, are useful for inferring the morphology of the outer integument from the relative position of the micropyle to the hilum in seed fossils. The oldest (early Cretaceous) probable nymphaealean seeds had the micropyle-hilum complex, suggesting that the hood-shaped outer integument may be primitive in the Nymphaeales. This needs to be tested by examination of this feature in other groups of basal angiosperms.Key words: developmental morphology; evolution; integument; micropyle-hilum complex; ovules; Nymphaeales; seeds.Bitegmic and anatropous ovules are common in basal angiosperms and are usually considered to be primitive in flowering plants as a whole (Stebbins, 1974;Bouman, 1984;Cronquist, 1988;Takhtajan, 1991;Johri, Ambegaokar, and Srivastava, 1992). Only a few authors regard anatropy as derivative and orthotropy as ancestral (Bocquet and Bersier, 1960). It has been suggested that the outer integuments are cup shaped and asymmetrical (Bouman, 1984). However, recent developmental and morphological studies have shown that in many basal angiosperms the outer integument is sharply asymmetric and hood shaped, that is, it is lacking on the concave (funicular) side of the ovule (Matsui, Imaichi, and Kato, 1993;Umeda, Imaichi, and Kato, 1994;Imaichi, Kato, and Okada, 1995;Igersheim, 1997, 1999;Endress, 1997, 1998; see also Johri, Ambegaokar, and Srivastava, 1992).The origin of bitegmy has been variously interpreted in contrast to the agreement on the origin of the first (inner) integument by fusion of telomes (Herr, 1995). Crane (1985Crane ( , 1986 and Doyle and Donoghue (1986, 1987) postulated that the outer integument is derived from the leafy lamina of a Caytonialike ancestor, while the carpel enclosing ovules is derived by lateral expansion of its leaf axis. It is also hypothesized that the bitegmic ovules have been derived from unitegmic and orthotropous ovules of glossopterid-like gymnosperms by the enclosure of the unitegmic ovules by the ovuliferous leaf to form the outer integument (Stebbins, 1974;Dahlgren, 1983;Kato, 1990;Stewart and Rothwell, 1993;Umeda, Imaichi, and Kato, 1994;Imaichi, Kato, and Okada, 1995;Doyle, 1996). Kato (1991) also speculates that the anatropy is an extreme modification of the hyponastic curvature of leaves (ovuliferous leaf). However, the origin of the outer integument and the origin ...

Section: Discussionmentioning

confidence: 70%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Developmental morphology of ovules and seeds of Nymphaeales

Yamada

2001

American J of Botany

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“…Consequently the outer integument connects the funicular outgrowth on the inner side (Fig. 6A) where the cell files of the two lie at nearly right angles giving rise to a boundary (Umeda et al 1994; for a similar cell alignment pattern in Liriodendron tulipifera, see Matsui et al 1993). The outer integument grows longitudinally to the nucellus and transversely to the funiculus on the lateral sides and consequently overgrows the funicular outgrowth (Fig.…”

Section: Discussionmentioning

confidence: 93%

“…Cabombaceae, Austrobaileyaceae, Trimeniaceae, Schisandraceae, many basal monocots, Winteraceae, Aristolochiaceae, Lactoridaceae, Degeneriaceae, Annonaceae, Idiospermaceae, most of Monimiaceae, Lauraceae, and Hernandiaceae), the outer integument is lacking on the funiculus (Yamada et al 2001a(Yamada et al , 2001b, in other words, semiannular Endress 1997, 1998;Igersheim et al 2001). Recent developmental studies have shown that the outer integument is semiannular at initiation and subsequently becomes hood-shaped in Cabombaceae (Nymphaeales); Austrobaileyaceae, Trimeniaceae (ITA); Annonaceae, Degeneriaceae, Eupomatiaceae (Magnoliales); and Winteraceae (Winterales) (Matsui et al 1993;Umeda et al 1994;Imaichi et al 1995;Yamada et al 2001a;T. Yamada, unpublished data).…”

Section: Introductionmentioning

confidence: 96%

The outer integument and funicular outgrowth complex in the ovule of Magnolia grandiflora (Magnoliaceae)

Yamada

Journal of Plant Research

2003

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The development of the outer integument and funicular outgrowth in the ovule of Magnolia grandiflora was examined by microtomy and scanning electron microscopy to reveal the morphology and evolution of the outer integument, a novel angiosperm structure. Early in development the outer integument is semiannular, decurrent to the lateral sides of the funiculus, and extends downwards beyond the funicular outgrowth that forms in the gap of the outer integument, and is transverse to the funiculus. The outer integument then overgrows the funicular outgrowth perpendicularly to the funiculus to form a micropyle together. The hood-shaped outer integument and the funicular outgrowth compose an envelope complex, and the interpretation of a single cupular outer integument is not supported. This envelope complex may differ from the cupular outer integument of other angiosperms, e.g., Nymphaeaceae, suggesting independent origin of apparently cupular outer integuments and hood-shaped outer integuments. Anatropous curving is due mainly to differential growth of the chalaza. The bistomic micropyle of Magnoliaceae seems to represent a derived character state, compared to an endostomic micropyle.

Ovular development and morphology of the outer integument of Magnolia grandiflora (Magnoliaceae)

Umeda

1994

American J of Botany

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Ovular development of Magnolia grandiflora was examined to determine the morphology of the outer integument. At the time the ovular primordium begins incurving, the outer integument is initiated subdermally, and later the inner integument arises from the dermal layer. Whereas the inner integument is annular, the outer integument is formed as a semiannular rim interrupted on the concave side of the funiculus. Later the outer integument becomes a hood‐shaped envelope. The obturator is formed as a transversely elongate outgrowth on the concave side of the funiculus and intervenes in the gap of the outer integument. During further development the inner integument produces several distal lobes, and the outer integument becomes bilobed. The exostome is a transverse slit with a middle notch, formed by the outer integument and the obturator. Presumed wide occurrence of the hood‐shaped outer integument in primitive families suggests that it is a primitive state. The outer integument is compared with the ovuliferous sporophylls of the glossopterid and caytonialean seed ferns.