蓮華池桑寄生種子之初期存活率: 寄主樹種、枝條徑級、與相對接種位置之影響

Early Survival Rate of Mistletoe Seeds (Taxillus tsaii): Effects of Host Trees, Branch Diameter, and Relative Inoculating Site

賴勁廷(Jing-Ting Lai)

指導教授 ： 丁宗蘇

國立臺灣大學/生物資源暨農學院/森林環境暨資源學研究所/碩士(2012年)

https://doi.org/10.6342/NTU.2012.00001

摘要

桑寄生與寄主樹木之間的相容性，是桑寄生族群分布與種子傳播的重要影響因子，且在寄生初期可分成桑寄生種子的附著、發芽、及固著器建立三個階段來探討。為探討影響蓮華池桑寄生(Taxillus tsaii)與寄主間的相容性，我自2008年7月至2009年4月，於蓮華池研究中心園區內選取14種樹種，人為接種2100顆蓮華池桑寄生種子，並記錄每顆種子的附著、發芽以及初期存活狀況。這14種樹種為山櫻花(Prunus campanulata)、橄欖(Canarium album)、泡桐(Paulownia fortunei)、印度栲(Castanopsis indica)、千年桐(Aleurites montana)、油茶(Camellia oleifera)、白匏子(Mallotus paniculatus)、野桐(Mallotus japonicus)、樟樹(Cinnamomum camphora)、土肉桂(Cinnamomum osmophloeum)、小西氏石櫟(Pasania konishii)、牛樟(Cinnamomum micranthum)、台灣肖楠(Calocedrus formosana)、及廣葉南洋杉(Araucaria hunsteinii)。每種樹種選取5棵樹木，每棵樹木選取3種徑級枝條(6-15 mm, 16-25 mm, 26-35 mm)，並在每個枝條上由末梢向主幹依序接種10顆種子。主要研究目的為探討樹種、枝條徑級、接種位置對桑寄生種子的附著率、發芽率、以及初期存活率的影響，並比較實驗所得的初期存活率與野外實際被寄生率的關係。結果發現，不同樹種對蓮華池桑寄生種子接種後第69天的附著率及發芽率，及對接種後第223天的種子存活率，皆有非常顯著的影響。枝條上的相對接種位置，對桑寄生種子的附著率、發芽率以及存活率也有顯著的影響，但解釋程度較低。不同枝條徑級對桑寄生種子的附著率、發芽率以及存活率則沒有顯著影響。由結果推論，桑寄生種子的附著率與發芽率，受不同樹種的表皮物理結構與化學成分，及其不同樹形所影響的微環境因子，因而在不同樹種上有顯著差異。接種後第223天的種子存活率，則主要受附著率與發芽率的影響。比較實驗所得桑寄生種子在各樹種的初期存活率與實驗樹種在野外實際被寄生程度，發現兩者之間沒有顯著相關。本研究也發現到某些樹種有樹皮剝落、樹脂包埋等等機制，使桑寄生種子苗無法順利成長。因此，桑寄生與寄主樹木間的相容性，會受到寄主樹皮物理結構、化學成分、生理特性、及特殊防禦機制的影響，也會受到不同生長形態所造成的微環境差異影響。桑寄生野外族群的成功建立，應主要取決於種子傳播者的停棲習慣所造成種子雨分布差異，以及桑寄生種子苗與寄主的後續存活率。與桑寄生相容性高的寄主，可能因為缺乏種子雨或微環境因子不適合，而沒有被成功寄生。

關鍵字

桑寄生 ； 種子存活 ； 種子傳播 ； 相容性 ； 固著器

並列摘要

Compatibility between mistletoes and host trees is a major factor in determining seed dispersal and population distribution of mistletoes. Early establishment of mistletoes on host trees could be divided into (1) seed adhesion, (2) germination, and (3) holdfast stages. I inoculated 2100 seeds of Taxillus tsaii on 14 tree species (Prunus campanulata, Canarium album, Paulownia fortunei, Castanopsis indica, Aleurites montana, Camellia oleifera, Mallotus paniculatus, Mallotus japonicus, Cinnamomum camphora, Cinnamomum osmophloeum, Pasania konishii, Cinnamomum micranthum, Calocedrus formosana, and Araucaria hunsteinii) in Lien-Hwa-Chi Research Center and recorded their adhesion, germination, and survival from July 2008 to April 2009. Each host tree species had five replicate trees and I inoculated 10 seeds sequentially on each branch of three diameter classes (6-15 mm, 16-25 mm, 26-35 mm) of each tree. Main objectives of this study were to examine the effects of host species, branch diameter, and relative inoculation site on the rates of adhesion, germination, and early survival of mistletoe seeds and compare the early survival rate of seeds with actual rate of mistletoe establishment in the study site. Results showed that host species had significant effects on the adhesion rate and germination rate of 69 days after inoculation and the early survival rate of 223 days after inoculation. Relative inoculation position also had significant but less prominent effects on the adhesion rate, germination rate, and early survival rate. By contrast, branch diameter had no significant effect on the adhesion rate, germination rate, and early survival rate of mistletoe seeds. The results suggest that the variations in adhesion rate and germination rate of mistletoe seeds among different host species were mainly affected by different physical structures and chemical compounds on barks of tree species and various microclimates caused different tree shapes of species. Early survival rate was mainly determined by the adhesion rate and germination rate and had no significant correlation with the actual rate of mistletoe establishment in the study site. I observed that some of the tree species had mechanisms of peeling bark and embedding resin to prevent establishment of mistletoes. Therefore, the compatibility between mistletoes and host trees was affected by host bark structure, chemical composition of bark, physiological characteristics, defense mechanisms, and micro-environmental condition caused by tree shapes. The establishment of mistletoes in field should be mainly affected by seed rain distribution, which is determined by habits of seed dispersers, and compatibility between mistletoes and host trees. Mistletoe seeds might fail to parasitize highly-compatible hosts due to lack of seed rains and unfavorable micro-environment.

並列關鍵字

compatibility ； holdfast ； mistletoe ； seed dispersal ； seed survival

參考文獻

張修銘、賴勁廷、丁宗蘇，2008。啄花鳥對蓮華池桑寄生的種子散播。林業研究專訊85號。15卷，5期，16–19頁。

Chiu, S.-T. 1996a. Notes on the genus Taxillus van Tieghem (Loranthaceae) in Taiwan. Taiwania 41: 154–167.

Chiu, S.-T. 2005. The hyperparasitism by Taxillus tsaii S. T. Chiu (Loranthaceae). Collection and Research 18: 51–63.

Arruda, R., Carvolho, L. N., and Del-Claro, K. 2006. Host specificity of a Brazilian mistletoe, Struthanthus aff. polyanthus (Loranthaceae), in cerrado tropical savanna. Flora 201: 127–134.

Aukema, J. E. and Martinez del Rio, C. 2002a. Mistletoe as parasites and seed-dispersing birds as disease vectors: current understanding, challenges and opportunities. In: Levey, D. J., Silva, W. R., and Galetti, M., eds. Seed Dispersal and Frugivory: Ecology, Evolution and Conservation. Oxford, UK: CAB International, 99–108.