The Hyperparasitism by Taxillus tsaii S. T. Chiu (Loranthaceae)

蓮華池寄生的重寄生現象

邱少婷(Shau-Ting Chiu)

《Collection and Research》 18期 (2005/12) Pp. 51-63

https://doi.org/10.6693/CAR.2005.18.8

摘要

There are no records of the hyperparasitism by Taxillus tsaii S. T. Chiu in Loranthaceae to date. Two cases those were found at Lien-Hua-Chih in the Nantou County, the hosts of T. tsaii were Viscum angulatum Heyne and Loranthus delavayi Van Tieghem. Specimens were deposited in the Botanical Herbarium of the National Museum of Natural Science at Taichung, Taiwan (TNM). The anatomy of the endophytic system in this case showed that the haustorium had progressively grown into the cambial cylinder and had penetrated the secondary xylem of the host branches. The xylary strands derived from the haustorium periclinally extended and centrifugally expanded in the host xylem. The penetration had induced thinning the host's cell walls of the invaded tissue, enhancing cytoplasm density, forming conspicuous plasmodesmata and pits, and triggering cell division. This differs from the development of the endophytic system in Phoradendron and Arceuthobium, whose sinkers derived from the cortical strands penetrate inwardly. The xylary strand and centrifugal outgrowth consisted of parenchyma with ergastic granules and a small amount of vascular tissue. It is possible to increase the water absorption and/or water storage with a high solute concentration in parasite tissues. This study also indicates that the occurrence of hyperparasitism in T. tsaii may be related to the diet and defecation of flowerpeckers and the phenology and seed germination of mistletoes. The majority of T. tsaii shows the primary parasitism but the hyperparasitism by this species also possibly occurs.

關鍵字

Hyperparasitism ； Loranthaceae ； mistletoes ； Taxillus ； woody parasites

並列摘要

桑寄生科（Loranthaceae）的蓮華池寄生（Taxillus tsaii S. T. Chiu）至今並無重寄生（hyperparasitism）記錄，臺灣學者僅有兩次目擊發現杜鵑寄生（Taxillus rhododendricolus (Hayata) Dancer）寄生於松寄生（Taxillus matsudai (Hayata) Danser）和臺灣槲寄生（Viscum alniformosanae Hayata）。本研究主要於南投縣魚池鄉蓮華池研究中心發現蓮華池寄生寄生於柿寄生（Viscum angulatum Heyne.）和大葉榿寄生（Loranthus delavayi Van Tieghem）的重寄生現象，標本存於國立自然科學博物館植物標本館（TNM），館號：S14101，採集號：邱22330。在此重寄生現象中，蓮華池寄生的寄生系統深入柿寄生的皮層、韌皮部、形成層及木質部，主要以木質部為侵入範圍。吸器侵入寄主枝條的木質部中，其衍生的木質束（xylary strands）平周延伸，其分支則向外擴伸；與其他桑寄生類（如Phoradendron、Arceuthobium）不同，其他寄生的主要侵入在皮層和韌皮部，衍生之下沈器（sinkers）再深入形成層和木質部。組織交接部的寄主細胞先增生現象、細胞壁薄、細胞質濃，後瓦解或產生填充細胞。此在寄主內的內生系統（endophytic system）主要是木質部系統外環圍著含大量澱粉粒的薄壁細胞組成，侵入的木質束分支亦有小單位的木質部和薄壁細胞構成，推測此系統以增強水分之掠奪為主。根據啄花鳥類的食性、排便行為及桑寄生類的物候性（phenology）、種子萌發率，推測此重寄生現象只是偶發事件，蓮華池寄生主要仍為初級寄生植物，但蓮華池寄生吸器若能侵入寄主，其延伸能力很強，故其重寄生現象發生仍然是可能性極高的。

並列關鍵字

木本寄生植物 ； 重寄生 ； 桑寄生 ； 桑寄生科 ； 鈍果寄生屬