臺灣紅豆杉種子物候學

Seed Phenology of Taiwanese Yew (Taxus sumatrana (Miq.) de Laub.)

林彥佑(Yan-You Lin)

指導教授 ： 黃玲瓏

國立臺灣大學/生命科學院/生態學與演化生物學研究所/碩士(2011年)

https://doi.org/10.6342/NTU.2011.10625

摘要

本研究的主旨在探討臺灣紅豆杉 (Taxus sumatrana (Miq.) de Laub.) 的種子物候學，將種子成熟的各發育階段之形態與解剖構造釐清後，輔以物候發育模式，探討該物種發育階段與氣候之間的相關性。
臺灣紅豆杉為源自第四紀冰河期的孑遺植物，分布在臺灣、中國東南與東南亞等地之高山地區。其雌毬花形態特殊，僅具單一胚珠。本研究材料於2009年9月至2011年4月分別採自烏石坑與八仙山兩種子園，以及原生棲地瑞岩溪谷地每月採集1-2次。就外部形態的初步觀察，臺灣紅豆杉雌生殖芽在每年八月底至九月初抽出後過冬，並於隔年三月開始發育，經過授粉、受精之後，種子於9月底至10月中成熟，成熟種子為紅色假種皮所包被。原生地的種子結實率較高，可達19%，各時期胚珠掉落的比例也較低。2010年3月到4月於種子園所採集的樣本有大規模胚珠掉落的現象，導致當年種子產量極低，烏石坑約12%，八仙山約僅6%。
臺灣紅豆杉胚珠發育至種子成熟的過程，根據解剖構造的觀察結果，可分為五個主要時期： (I) 珠心期、 (II) 大孢子母細胞與四分孢子期、(III) 配子體發育期、 (IV)、藏卵器發育期、(V) 胚胎發育與種子成熟期，每個主要時期可再細分為一至三個小期 (a-c)。比較三個生育地之觀察結果顯示，原生地樣本之珠心期 (I) 與大孢子發育期 (II)發生的時間較種子園早，但 (III)-(V) 時期則大致同步。
本研究根據溫帶地區對於裸子物候研究使用的預測模式，配合氣溫資料發育的時程，推測上述結果應為種子園林木受到冷激 (Chilling)不足，使休眠延後打破，或可能因為冬季過暖而無進入休眠。待隔年春天時，雖休眠延後打破，但低海拔的高溫能夠提供林木足夠的積溫得以繼續發育。我們亦發現每個發育階段所需的積溫呈現線性的趨勢，且年均溫越高此斜率越高。
我們發現低海拔地區的臺灣紅豆杉，因為前兩個發育時期 (I-II) 開始的時間點延後，造成胚珠發育與花粉飛散的時間不同步，使得授粉成功率降低，進而造成較低的結實率。

關鍵字

臺灣紅豆杉 ； 物候 ； 冷激 ； 積溫 ； 種子發育 ； 胚珠發育

並列摘要

Abstract
The object of this research is to investigate seed phenology of Taiwanese yew (Taxus sumatrana (Miq.) de Laub.). We tend to clarify the morphology and anatomy characteristics of each seed developmental stage and then we use phenology models to discuss the relationship between these developmental stages and climate data.
Taiwanese yew is a glacial-remaining conifer from Quaternary (250m.y.), which distributes in high elevation in Taiwan, Southeast China and Southeast Asia. The seed cone of Taiwanese yew features its single ovule. The duration of this research was started from September 2009 to April 2011. We collected the female reproductive branch samples from seed orchards in Wushiken and Basianshan every two weeks to every month; besides, in a natural habitat, Reyenshih, every one or two months.
The morphological observation showed that, the female reproductive buds (ovules) of Taiwanese yews flush in late August to early September, and these buds then stay in the winter with nucellus form. The buds start to develop in early March next year. After pollination and fertilization; the embryos start to mature inside the seeds from late September to middle October. Mature seeds are enclosed by red arils. In natural habitat, Reyenshih, the seed maturation ratio is higher (19%), i.e. The ratio of dropping out in each stage is lower. However, the samples taken from seed orchards had a massive drop-out in March and April in 2010, resulting in lower productivity, Wushiken (11%), Basianshan (6%).
According to the anatomical characteristics of developing ovules, the seed development of Taiwanese yew is separated into 5 main stages: (I) Nucellus stage, (II) Megaspore mother cell & 4 nucleate stage, (III) Megagametophyte stage, (IV) Archegonium stage and (V) Embryogenesis and seed maturing stage. These stages are further separated into 1 to 3 sub stages (a-c).
According to the observation on different habitat sites, we found that the ovule development (stage I and II) was earlier in the native site than in the seed orchards; however, the rest of three stages (III-V) were approximately synchronized.
Winter chilling and spring warming model were applied to this research, which is widely used in discussing the relationship between temperature data and developmental stages. of temperate coniferous species.
In general, temperate tree species require enough chilling to stimulate the differentiation of reproductive buds. According to the results, seed orchards in lower altitude cannot provide suitable chilling condition to these trees to break dormancy in suitable time, or even no dormancy. However, despite the dormancy-break in the next spring, the acumination of degree-days (degree day sum) is quicker in lower elevation than that in higher elevation, so the trees in low elevation can receive more energy. Therefore, the last three developmental stages in the seed orchards were almost synchronized with those in the natural habitat.
We also found the degree-day requirement of each stage shows a linear trend. However, according the observation of anatomy characteristics, the low seed maturation rates in seed orchards results in the unsynchronized development of ovule and pollen distribution.

並列關鍵字

Taxus ； yew ； phenology ； chilling ； degree day sum ； seed development

參考文獻

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