台灣肖楠之生殖週期

Reproductive Cycles of Calocedrus formosana

鍾振德(Jeng-Der Chung) ； 郭幸榮(Shing-Rong Kuo)

《台灣林業科學》 20卷4期 (2005/12) Pp. 315-329

https://doi.org/10.7075/TJFS.200512.0315

摘要

台灣肖楠每年從三月至十月底萌生新葉與側枝。六月中旬到七月初，雄毬花萌生於枝條中問，並持續發育至九月底。六月底到七月中旬，雌毬花由末梢腋生營養芽所轉變。苞葉出現時，有絲分裂快速增加，雌毬花已顯而易見。軸上每個苞鱗片有2個胚珠。台灣肖楠雄毬花與雌毬花在二月中旬結束休眠，小孢子於二月中旬萌生，授粉約在二月底。授粉期約為兩個星期。4個胚珠同時分泌授粉滴，花粉掉落後被授粉滴帶進珠孔。花粉抵珠心前，於授粉滴發芽與伸長。授粉滴在珠孔消失後，珠被之細胞伸長封住珠孔之孔道。花粉管在五月底穿透珠心，此時花粉管的生長緩慢，到六月上旬，花粉管快速的伸長到藏卵器頸細胞的表面。二月底大配子開始萌生，但此時雌配子體並未成熟，直到五月底之前都還未授精。雌配子體形成藏卵器群，內有4~6個藏卵器，通常只有1~2個授精。授精後，胚胎在前胚期的發育與藏卵器的大小與形狀，存有很大的差異。台灣肖楠的胚胎發育屬於分裂性多胚。胚在八月中旬成熟，大部分種子在九月到十月飛散完畢。每粒毬果具有潛力的種子4粒，但平均僅1~2粒為飽滿的實粒。

關鍵字

雄毬花 ； 雌毬花 ； 授粉 ； 授精 ； 胚胎發育

並列摘要

Vegetative shoots of Calocedrus formosana continually initiated leaves and lateral branches from early March until the end of October. Pollen cones were initiated on proximal vegetative shoots from mid-June to early July, and development continued until the end of September. Seed cones were initiated on newly formed, distal axillary vegetative shoots from late June to mid-July. Transition to a seed-cone apex was marked by an increase in mitotic activity followed by bract-scale initiation. Usually 2 ovules were initiated in the axil of each bract scale. Pollen cones and seed cones ended dormancy in early February, microsporogenesis occurred in mid-February, and pollination occurred in late February. Pollination occurred during a 2-wk period. Pollination drops were exuded from 4 ovules at one time. Pollen contacting the pollination drop was rapidly taken in. Pollen frequently germinated and elongated in the pollination drop within the micropyle before reaching the nucellus. The pollination drop was withdrawn into the micropyle which was later sealed by enlargement of the cells lining the micropylar canal. Pollen tubes penetrated most of the nucellus during late May, then pollen-tube growth slowed until early June when the pollen tubes quickly extended to the surface of the neck cells. Mega-sporogenesis occurred in late February, but female gametophytes did not mature and fertilization did not occur until late May. An archegonial complex formed containing 4~6 archegonia, of which several were usually fertilized. Proembryo development varied depending upon the size and shape of the archegonia. Cleavage polyembryony was observed in this plant. Embryos had matured by mid-August, and most seeds were shed in September and October. The potential seed set was only 4 seeds per cone and filled seeds averaged only 1 or 2 per cone.

並列關鍵字

pollen cone ； seed cone ； pollination ； fertilization ； embryogenesis