Development of ovulate cones from initiation of reproductive buds to fertilization in Cephalotaxus wilsoniana Hay.
Cephalotaxus wilsoniana Hay, is endemic to Taiwan. This study was performed morphologically and anatomically to investigate reproduction in this species for the purpose of conservation. The duration from reproductive bud formation to fertilization in C. wilsoniana lasts about one year and five months. Buds are initiated in late January and differentiate into one vegetative bud and 3 female cones in late February. A female cone is constructed with 4 pairs of decussate opposite bracts. A small ridge-like secondary axis sits on the axil of each bract. Two ovules are borne on both sides of each secondary axis. A lysogenous pollen chamber begins to be formed from the degenerative tissues on the top end of the nucellus in early March. In late March the megasporogenous tissue is differentiated in the core center of the nucellus, and the micropyle closes gradually after pollination. By late July, pollen tubes have developed in the pollen chamber, and the megaspore mother cell appears. Then the functional megaspore becomes active in mid-October. The 8 free nucleate macrogametophyte appears in late December. From January to late March of the following year, the elliptical cyst-like female gametophyte keeps growing through continuous divisions of its free nuclei. The cyst layer of protoplast thickens in early April. In mid-April, cell walls begin to form among free nuclei. The archegonia are initiated in late April. Pollen tubes extend their tips to the macrogametophyte in early May, and each tube with 2 spermatozoids reaches a mature archegonium with an egg needed to perform fertilization in late May. Generally, only 1-(3) ovules in each cone can become mature.
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Department of Forestry, National Taiwan University, Taipei, ROC.
Wang
Y F
YF
D010946:Plants, Medicinal / Q000502:physiology*; D013624:Taiwan