The Embryology of Nyssa sinensis Oliv. (Nyssaceae)

Chen Ling-Jing, Qian Nan-Fen, Wang Fu-Hsiung

Received:1900-01-01 Revised:1900-01-01 Online:1991-11-10 Published:1991-11-10
Contact: Chen Ling-Jing

Abstract:

The flower develops in March and blossoms in early May in Nanjing. The

cytokinesis of microsporocytes is simultaneous and most tetrads are tetrahedral. The tapetum

is secretory and the nuclei become polyploid at last. The style is solid and most ovaries are

unilocular, rarely bilocular. The ovule is pendulous, anatropous and unitegmic. The nucellus is

pseudocrassinucellate. An obturator formed by transmitting tissue covers the micropyle. The

raphe vascular strand extends into the integument when it reaches the chalaza and on a whole

keeps a “U” shape. The endothelium cell is uninucleate. In most cases no nucellar cap is

formed. No hypostase is found below the embryo sac. The archesporium is one-celled. The

embryo sac development conforms to the Polygonum or Allium types. The degeneration of

the megaspores in the linear tetrad usually occurs from the chalazal toward the micropylar

end. Two synergids persist during fertilization. Three antipodal cells are uninucleate and

ephemeral. Two polar nuclei fuse at the time of fertilization. The fertilization type accords

with porogamy. The syngamy is premitotic. The development of endosperm is cellular.

The initial four successive divisions of the primary endosperm cell are transverse-vertical-

transverse-transverse subsequently, giving rise to sixteen cells of the early endosperm. The

mature embryo is straight and nearly as long as the endospermous seed. The cotyledons are

more or less cordate at base. The seedoat is thin and composed of 5-11 layers of compressed

cells. Neither embryo nor endosperm contain the alkaloid camptothecine.

The major similarities of Nyssa sinensis to the American nyssas in embryology, which

may be a counted as the generic features, are the polyploid tapetum cells, the unitegmic ovule

with U-shaped vascular strand, the direct enlargement of the archesporial cell to produce the

megasporocyte, the pseudocrassinucellus, the usual absence of the nucellar cap, the

Polygonum or Allium type of the embryo sac development, the first degeneration of the

metachalazal megaspore, the ephemeral antipodal cells, a single nucleolus in the nucleus of

the primary endosperm cell, the more or less cordate base of the cotyledons.

Key words: Nyssa sinensis div., embryology

Chen Ling-Jing, Qian Nan-Fen, Wang Fu-Hsiung. The Embryology of Nyssa sinensis Oliv. (Nyssaceae)[J]. .

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