An Embryological Investigation and Systematic Position of Cephalotaxus oliveri Mast.

Abstract

Abstract:

The tapetum is of the secretory type. After breakdown of callose wall around

tetrads, tapetal cells degenerate quickly and disappear completely at the late stage of micros-

pore development. The mature male gametophyte is of a tube cell and a generative cell, with-

out prothallial cells. The pollen tube lodging in the nucellus contains a spermatogenous cell, a

tube nucleus and a sterile cell before entering domancy. In the following spring the pollen

tube grows fast, and reachs the female gametophyte when the archegonia are mature. The sper-

matogenous cell enlarges obviously, and the cytoplasm is very dense in the centre of the cell

and shows well-marked radiations from this region to the periphery, when it divides to form

two sperm cells of unequal size, while the tube nucleus and the sterile cell degenerates and sub-

sequently disappears. After 12th simultaneous divisions the cell wall of the female gametophyte

forms from the periphery to the centre. When the central cell has divided to form the egg and

the ventral canal nucleus ,its cytoplasm becomes very dense and numerous bodies, similar to nu-

cleoli in appearance, occurs. The sperm and the egg come together at metaphase of the first

division of the zygote. The wall formation of proembryo initiates at the 16-nucleate stage.

The features of the mature embryo are as follows: (a) The cotyledons are very long, with

their length about four fifths of that of the whole embryo, (b) the embryonal axis is so short

as to cover only about one sixth of the cotyledons, (c) there is no typical pith, (d) the root cap

is well-developed and consists of about 10-15 layers of cells which are very large and are full

of starch grains and (e) the epidermis cells only extend to the upper part of the root cap. It

is concluded that Fu's (1984) suggestion, that the Cephalotaxus be divided into two sections, Ce-

phalotaxus and Pectinatae, is supported by the present embryological investigation on C. oliveri.

Key words: Cephalotaxus, Embryology, Phylogeny

Li Ying, Wang Fu-Hsiung, Chen Zu-Keng. An Embryological Investigation and Systematic Position of Cephalotaxus oliveri Mast.[J]. .

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An Embryological Investigation and Systematic Position of Cephalotaxus oliveri Mast.

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