Vascular plants - vascular plants

A group of plants with vascular bundles, also known as vascular plants. Among green plants, ferns do not have a distinct organ called a flower, and do not produce seeds, so they are usually distinguished from seed plants, but since both have well-developed vascular bundles as a system suitable for terrestrial life, they are treated as a single taxonomic group. This was first proposed by Swiss botanist De Candolle in his "Elements of Botany" (1813), and broadly divided the plant kingdom into two. In this method, ferns and seed plants were classified as vascular plants, and mosses, fungi, algae, and lichens were classified as cellular plants. However, mosses also have stems and leaves, and in the center of the stems are found groups of long, thin cells (vascular bundles) that correspond to vascular bundles, and they are thought to have a system suitable for terrestrial life, but compared to ferns and higher plants, their degree of differentiation is still low, and they cannot be called vascular plants. Vascular plants have a life cycle in which sexual and asexual generations alternate, with the asexual generation being particularly well developed and having aboveground parts with clearly differentiated leaves and stems. Spores are produced in the leaves, but in seed plants these take on a special function as sporophylls, and in these the stamens differentiate into microsporophylls and pistils into megasporophylls, which come together to produce flowers. The sexual generation which produces gametophytes is extremely small and parasitizes the asexual generation. On the other hand, cellular plants include different taxonomic groups, which can be problematic to handle, but vascular plants are a unified phylogenetic group and are often used when dealing with ferns, gymnosperms, and angiosperms as a whole.

[Akiko Sugiyama]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

維管束をもった植物群のことで、管束植物ともいう。緑色植物のなかで、シダ植物には花とよばれるはっきりした器官がなく、種子を生じないので、普通は種子植物とは区別されるが、ともに陸上生活に適した体制として、よく発達した維管束をもつので、これを一つにまとめて扱おうとする分類群である。スイスの植物学者ド・カンドルが『植物学基本』（1813）で初めて提唱し、植物界を二つに大別した。その方法は、シダ植物と種子植物を維管束植物Vascularesとし、コケ植物、菌類、藻類、地衣類を細胞植物Cellularesにまとめるものであった。しかしコケ植物にも茎と葉があり、茎の中心部には維管束に相当する細長い細胞群（道束）がみられ、一応陸上生活に適した体制をもつと考えられるが、シダ植物以上の高等植物に比較して、まだその分化の程度は低く、維管束植物とはいえない。維管束植物では、有性世代と無性世代の交代する生活環がみられ、とくに無性世代はよく発達して、葉と茎がはっきり分化した地上部をもっている。胞子は葉に生じるが、種子植物では胞子葉としての特別な働きをもつようになり、小胞子葉として雄ずい、大胞子葉として雌ずいが分化し、これが集まって花をつくる。配偶体を生じる有性世代は極端に小さく、無性世代に寄生する。一方の細胞植物は異なった分類群を含むので、扱いに問題はあるが、維管束植物は系統分類上のまとまりがあり、シダ植物、裸子植物、被子植物を一括して扱うときには便利なので、よく用いられる。

［杉山明子］

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