台灣稀有食蟲植物-長葉茅膏菜生理生態特性之探討

An ecophysiological study of Drosera indica, a rare carnivorous plant in Taiwan

黃閎義(Hung-Yi Huang)

指導教授 ： 高文媛

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(2015年)

https://doi.org/10.6342/NTU.2015.01188

摘要

長葉茅膏菜 (Drosera indica) 為一年生草本植物，全株具有會分泌黏液之腺體，可捕捉獵物。目前台灣本島僅剩竹北蓮花寺濕地有較穩定族群，但須透過人為管理才得以維持。本研究：(1) 透過觀察野外、農場種植族群及石蠟切片等方式，了解長葉茅膏菜生活史及內、外部構造。(2) 使用穩定性同位素技術探討生長於濕地之長葉茅膏菜是否有透過捕捉獵物補充氮源，並用模式計算蟲源氮之比例；在台大農場進行隔蟲處理實驗，以探討獵物對長葉茅膏菜生理及生長之影響。(3) 假設濕地伴生植物過度生長限制長葉茅膏菜之族群數量，因此在該濕地進行除草及除草加翻土處理以驗證；並在台大農場及生長箱內進行光度及溫度操控實驗，以了解伴生植物影響長葉茅膏菜族群數量之可能機制。
觀察發現，濕地長葉茅膏菜大約於3月萌芽，5月開始開花，持續至10月左右結束生長季。植株高度變化很大 (15 ~ 50 cm)，與過去文獻紀錄有差異 (約20 cm)。花柱開裂呈Y字形，交錯於雄蕊之間，且花朵有日週期性開閉運動，可能會使柱頭沾附自花花粉。葉片上具有長、短柄腺體，長柄腺體是數百個細胞組成的複合體，分成頭狀構造及柄狀構造；短柄腺體是由8個細胞所組成。分析結果顯示野外長葉茅膏菜之穩定性氮同位素比值顯著高於伴生植物，代表其有不同的氮來源，估算植株約 46 ~ 58 % 的氮是從獵物獲得。而從隔蟲實驗結果得知：捕捉獵物可增加植株的氮含量及種子產量。蓮花寺濕地經除草及除草加翻土處理之樣方，土壤所接受到的光度及土壤溫度變化趨勢與控制組樣方不同，且兩種處理都有助於增加長葉茅膏菜族群數量。種子萌芽及生長環境光度操控實驗結果顯示：長葉茅膏菜種子需照光才會萌芽，且在低溫會有休眠現象；生長於高光環境植株會有較高的生物量及種子產量；生長於中光環境植株徒長且生物量及種子產量較低；多數低光環境生長植株未開花、結果即死亡。
綜合野外操控及光度、溫度生長實驗證實，在蓮花寺濕地由於伴生植物過度生長，使得長葉茅膏菜種子及植株無法接收到足夠的光度以萌芽及生長，導致族群數量下降，透過除草增加土表接受到的光照度可以有效提高族群數量，因此光度為限制野外長葉茅膏菜族群數量之重要環境因子，而土壤溫度是造成長葉茅膏菜有明顯生長季原因之一。

關鍵字

蓮花寺濕地 ； 食蟲植物 ； 長葉茅膏菜 ； 環境因子 ； 蟲源氮

並列摘要

Drosera indica is an annual herb with many glandular trichromes, which could secrete mucus to help capturing small arthropods. Currently in Taiwan island, its populations are only found in the wetland of Lienhwa Temple and maintained by artificial disturbance. There are 3 aspects of this study. (1) To understand life cycle, morphology and anatomy of leaf and root of D. indica, I observed wild populations and made histological section. (2) To investigate whether D. indica uptakes nitrogen from captured prey and to estimate the nitrogen (N) sources, derived from root (Nr) and prey (Np), I analysed stable nitrogen isotopes ratio (δ15N) of D. indica, accompanying plants and potential prey. I also grew D. indica in two environments, control and prey excluded, to examine if Np has beneficial effect on D. indica’s growth and reproduction. (3) I hypothesized that the overgrowth of accompanying plants in the wetland inhibited the population of D. indica. To test the hypothesis, I conducted weeding and weeding then rooting treatments at the habitat then examined the effect of these treatments on the population of D. indica and microclimates. I also studied the effects of light and temperature on seed germination and growth of D. indica to evaluate the underlying mechanisms responsible for the inhibition effect of accompanying plants on the D. indica population.
In the wetland, D. indica started germinating in March, flowering in May and continued blooming till October. The height of D. indica was about 15 ~ 50 cm, which was different from previous reports. Its flowers have 3 ~ 4 bifid styles, of similar height and entangling with stamens. Self-pollens might adhere on stigmata due to daily flower movement. There are many long and short stalked secretory glands on leaves. Long stalked secretory glands consist of stalked structure and head glandular. Short stalked secretory glands consist of eight cells. The δ15N of D. indica was significantly higher than that of accompanying plants indicating acquiring N source from prey, which was estimated about 46 ~ 58 % of all N content. The capturing of prey increased leaf [N] and the production of seeds of D. indica.
Results from field experiments revealed that pattern of variety of photosynthetic photon flux density (PPFD) and soil temperature differed between control and treated plots, and treated plots grew significantly more D. indica plants. Growth chamber experiments showed that seeds of D. indica could not germinate in dark, and remained dormant at low temperature. D. indica grown in high light environment had highest biomass and produced more seeds; those in medium light elongated and produced less seeds; most of those in low light died before flowering. Consequently, these results suggest that D. indica in wetland might not receive enough light for germination and growth due to overgrowth of accompanying plants. In conclusion, light is an important factor limiting the population growth while soil temperature plays an important role in starting the life cycle of D. indica in wetland.

並列關鍵字

Lienhwa Temple Wetland ； carnivorous plant ； D. indica ； microclimate ； nitrogen derived from prey

參考文獻

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