Higher Plants


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Higher Plants

 

(embryonic plants—Embryobionta, Embryophyta; shoot-bearing plants—Cormophyta, Cormobionta; and telomic plants—Telomophyta, Telomobionta), one of the two subkingdoms of the plant world, including at least 300,000 plant species of the groups (divisions) Tracheophyta (Psilophytaceae), Bryophyta (liverworts and mosses), Psilopsida (Psilotum and Tmesipteris), Lycopodiales, Equisetales, ferns, gymnosperms, and flowering plants, or angiosperms. Unlike lower plants, higher plants are complexly differentiated multicellular organisms adapted to life on the ground (with the exception of a few clearly secondary aquatic forms) and characterized by regular alternation of two generations: sexual (gametophyte) and asexual (sporophyte). Multicellular sporangia, in which fixed spores are formed, develop in the sporophytes of higher plants; sex organs (gametangia) develop in gametophytes. However, in some gymnosperms (the genera Gnetum and Welwitshcia) and all flowering plants gametangia disappeared in the course of evolution.

Sporangia are either identical or, more often, differentiated into two types—microsporangia and megasporangia; but gametangia are always of two types—male (antheridium) and female (archegonium). Antheridia and archegonia are protected by multicellular walls. The female gamete (egg cell) is always single and immobile. In higher plants the zygote develops into a multicellular embryo that passes through the first stages of development inside the female gametophyte. The sporophyte in higher plants is generally divided into three main organs: leaf, stem, and root.

Most higher plants develop special conducting tissue, xylem and phloem, which is reduced in some groups. There is an epidermis with a cuticle and typical stomata. The chlorophyll of higher plants does not contain additional pigments, and the photosynthesizing parts are green. Certain marine algae were the ancestors of the higher plants. Reliable fossil remains of higher plants are known beginning with the Silurian period.

REFERENCES

Golenkin, M. I. Kurs vysshikh rastenii. Moscow-Leningrad, 1937.
Krishtofovich, A. N. Paleobotanika, 4th ed. Leningrad, 1957.
Meier, K. I. Morfogeniia vysshikh rastenii. [Moscow] 1958.
Takhtadzhian, A. L. Vysshie rasteniia, vol. 1. Moscow-Leningrad, 1956.
Kozo-Polianskii, B. M. Kurs sistematiki vysshikh rastenii. Voronezh, 1965.
Lawrence, G. H. M. Taxonomy of Vascular Plants. New York [1960].
Engler, A. Syllabus der Pflanzenfamilien, 12th ed., vols. 1-2. Berlin, 1954-64.
Zimmermann, W. Die Phylogenie der Pflanzen, 2nd ed. Stuttgart, 1959.
Novak, F. A. VySSi rostliny. Prague, 1961.

A. L. TAKHTADZHIAN

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