2024 年 32 巻 1 号 p. 10-14
The Arecaceae family of plants accumulates a substantial amount of silicon, which helps to mitigate the harmful effects of stress caused by heavy metals, salts, and drought. This also leads to the formation of phytoliths in all parts of the palm. In this study, phytoliths from several palm leaflets were compared. In order to determine the relative abundance of phytoliths, slides containing 250 phytoliths each were observed by microscope. The samples were subjected to incineration at 550°C, ultrasonic treatment, 0.1 mol/L HCl treatment, and distilled water washing. Sago palm (Metroxylon sagu) phytoliths were identified as spheroid echinate symmetric morphotypes with diameters of <5 μm (1.2%), 5–10 μm (27.8%), 10–15 μm (48.8%), 15–20 μm (20.4%), and >20 μm (1.9%). These spheroid phytoliths were relatively larger than those of other palm species such as Phoenix roebelenii, Phoenix canariensis, and Pritchardia pacifica. The phytolith assemblages of sago palms were also distinguished by their symmetrical spheroidal shape and sharp spines. Meanwhile, Corypha umbraculifera and Washingtonia robusta produced both spheroid and ellipsoid phytoliths. Caryota maxima, Butia yatay, Dypsis lutescens, and Dypsis decaryi formed three types of phytoliths: spheroid, ellipsoid, and conical. Areca catechu, Cocos nucifera, Chamaedorea elegans, and Chamaedorea cataractarum produced both ellipsoid and conical phytoliths. Phytoliths of Hyophorbe verschaffeltii were identified as conical morphotypes only. We have proposed a schematic genealogical tree for Arecaceae based on the description (morphotypes and size distribution) of their phytoliths, using the results of this study.
