nucellus


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nucellus

the tissue within the OVULE of a plant, surrounded by INTEGUMENTS (1) and containing the EMBRYO SAC.
References in periodicals archive ?
Coe (1954) demonstrated that in Zephyranthes relatively insoluble carbon-containing compounds were concentrated in the cells of the nucellus except the hypostase, indicating that the impermeable hypostase compels water and food to pass around it.
1990) referred to a similar tissue in fruits of Phyllospadix (Zosteraceae) as a nucellar projection, the only part of the nucellus that persists for a while during fruit development, although it is eventually crushed in the mature fruit.
The proximal region of the nucellus is often several-layered.
In this case, the nucellus data are highly congruent with the rbcL tree, and an enlarged dermal region represents the most consistent apomomorphy for Lomandraceae.
In Tricyrtis the entire nucellus is narrow and elongated (Fig.
A vascular supply to the nucellus is extremely rare in angiosperms (Bouman, 1984), although there are occasional records of nucellar tracheids.
The term "haustorium" implies increased absorptive activity, and there is clearly an observable pattern of nucellus tissue degeneration, followed by invasion of endosperm, also present in our material of Cyanella (Fig.
1990), and in Lomandra (Lomandraceae) in the dermal nucellus tissue adjacent to the megagametophyte (Fig.
Postaments often relate directly to the Zuleitungsbahn of the pre-fertilisation ovule nucellus (see above).
In dicotyledons, postaments are common in Fagaceae, such as Quercus (Brown & Mogensen, 1972) and Nothofagus (Poole, 1952), where they represent a resistant remnant of nucellar tissue, linking the antipodals and vascular strand after the rest of the nucellus has degenerated.
Robertson (1976) referred to the persistent proximal part of the nucellus in the palm Jubaeopsis as a postament; however, this is not a column of tissue but simply a remnant basal region, and therefore correctly a podium.
In many monocotyledons parts of the nucellus enlarge or proliferate either before or after fertilisation, and have a role as a regulating or storage tissue for the megagametophyte and/or developing embryo.