A dicotyledonous plant family of the Chenopodiaceae order. There are said to be over 100 genera and 1,400 to 1,500 species. They are herbaceous or small shrubs distributed widely around the world, but many are halophilic plants and prefer to grow in dry areas such as deserts. For this reason, they are mainly distributed in the prairies of North America, the dry wastelands of Central Asia, Australia, the Arabian Peninsula, and the Pampas region of South America, where they form part of unique vegetation. Many of them have well-developed rhizomes, such as sugar beets. Their leaves are small, often fleshy and covered with hairs, and many of them are adapted to dry conditions. In addition, Salicornia arvensis, which grows in salt marshes, has a fleshy, jointed stem with a shape reminiscent of a cactus. Flowers can be bisexual or male and female. The petals are small and inconspicuous, usually five, but sometimes one to four, and some species have no petals at all. The number of stamens is usually the same as the number of petals, and there is one pistil, which is located above the ovary and produces one seed inside. Many plants contain oxalic acid or calcium oxalate crystals, including the world-wide weed Chenopodium album. Spinach and sugar beet are cultivated worldwide, and quinoa has a long history of cultivation as a food plant in the Andean highlands. Source: Encyclopaedia Britannica Concise Encyclopedia About Encyclopaedia Britannica Concise Encyclopedia Information |
双子葉植物アカザ目の1科。 100余属 1400~1500種あるとされる。世界に広く分布する草本ないし小低木であるが,多くは好塩性の植物で,砂漠などの乾燥地に好んで生える。このため主要な分布地は,北アメリカのプレーリーや中央アジアの乾荒原,オーストラリア,アラビア半島,南アメリカのパンパ地帯などで,特殊な植生の構成者となっている。根茎が発達するものが多く,サトウダイコン (砂糖大根)などが代表的である。葉は小さく,しばしば多肉で毛におおわれ,乾燥への適応を示すものが多い。また,塩性湿地に生えるアッケシソウ (厚岸草)などでは茎が多肉で節をなし,サボテンを思わせる形状をしている。花は両性花または雌雄花の別がある。花弁は小さく目立たず,通常5枚,ときに1~4枚で,花弁をもたない種類もある。おしべは通常花弁と同数,めしべは1本で子房上位,中に1個の種子をつくる。雑草として世界的に広がるアカザをはじめとして,植物体にシュウ酸やシュウ酸カルシウムの結晶を含むものも多い。ホウレンソウ (菠薐草),サトウダイコンなどは世界的に栽培され,また,キノア quinoaはアンデス高地での食糧植物として栽培の歴史が古い。
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