Horsetail , also segientera , maple , cuneiform ( lat. Equisetophýtina ) - a subdivision of higher spore plants of the fern department , previously housed in the now abolished Equisetophyta department.
| Horsetails | |||||||||||
 Horsetail large ( Equisetum telmateia ) | |||||||||||
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| International Scientific Name | |||||||||||
Equisetophytina Reveal , 1996 | |||||||||||
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Horsetails are characterized by the presence of shoots consisting of clearly defined segments ( internodes ) and nodes with whorled leaves. This feature is modern and fossil horsetails are very different from all other higher spore plants and resemble in appearance some algae ( char ), gymnosperms ( conifer ), or even flowering ( casuarina ) [1] .
Horsetails are peculiar plants. Many vegetative traits bring them closer to cereals . Apparently, among the ferns, horsetails are the most competitive, which is explained by numerous improvements in the vegetative organs: the stem of horsetails is articulate and grows in nodes (as in grasses); epidermis reinforced with silica ; the weight of the stem is facilitated by the presence of a central cavity; there are numerous strands of mechanical tissue that increase the strength of the stem; there are air cavities, allowing to adjust the supply of oxygen to underground and underwater parts; real vessels develop (as in angiosperms ); spores are equipped with special repulsive shoots (hapters), contributing to the loosening of the spore mass, and, consequently, the transfer of spores by the wind . Due to these structural features, horsetails, as in the remote Carboniferous period , continue to dominate in some biocenoses , mainly along the banks of water bodies. Horsetails also have another interesting feature: they have different sexes, and the development of male or female growths is predetermined by environmental conditions. In general, the worse the conditions, the greater the percentage of male growths formed. Thus, the tails demonstrate a transitional stage from typical equilus to typical mismatch [2] .
Biological description
Appearance
To the horsetail belong both extinct herbaceous and now living plants with a stem from several centimeters to several meters long, and tree-like extinct forms, reaching 15 m in height and trunk diameter of 50 cm [1] .
Anatomy
The conducting system of the stalk of the horsetail is represented by an actinosteal or arthrosteal, that is, an articulate stele , consisting of alternating between each other along the stem of different sections of the structure. The conductive elements of the xylem are represented by tracheids of various types, and in horsetails also by vessels . Phloem consists of sieve elements and parenchymal cells [1] .
Origins and Evolution
Horsetails appeared in the upper Devonian and were descended from the now extinct Rhinic ( Rhyniales ) or some plants close to them, but they reached their heyday in the Carboniferous period , when they were widely represented by a variety of woody and herbaceous forms . Together with lepidodendrons and tree ferns, horsetails took a large part in the formation of coal forests .
Fossil horsetails (for example, treelike Kalamits ) reached a height of 25 m, and a secondary xylem was found in their trunks. However, in Perm , their extinction begins, and, first of all, arboreal forms die out, so that only grassy horsetail is known from the Mesozoic . To date, only the Equisetum genus has been preserved from this entire large group.
Both extinct and modern horsetail are distinguished from all known plants by shoots composed by separate segments. The name “Articulate” comes from this specificity of the structure of their shoots, which are divided into distinct nodes and internodes, easily disintegrating into segments. The articulation is due to the whorled leaf arrangement and the presence of the intercalary meristem in the lower parts of the interstices, along which breaking occurs into segments.
Peculiar leaves are characteristic for modern horsetails - their leafy plates are strongly reduced to small dark, sometimes green or colorless teeth, and the well-defined vaginas have grown together into a common foamed vagina. The presence of strobilas in the form of spikelets is characteristic of the reproductive organs of the segmented, and only in some Paleozoic species - the sporiferous zones. In modern horsetails, the sporangiophores have a carapace form, while in the ancient, extinct, they had the most diverse form, except for the leaf-shaped. The overwhelming majority of horsetails are equal-pore plants and only a few extinct species were raznosporovymi.
Classification
The subpart of the articular, or horsetail, consists of three classes , the evolution of which was apparently independent, parallel paths - the two extinct classes Sphenophyllopsida , Cladoxylopsidae and the currently existing class Equisetopsida .
Notes
- ↑ 1 2 3 Plant Life, 1978 .
- ↑ Shipunov A. B. Spaniciform, psilotovye, uzhovnikovye and horsetails // Biology: School encyclopedia / Belyakova G. et al. - Moscow : BRE, 2004. - 990 p. - ISBN 5-85270-213-7 .
Literature
- Horsetails // Brockhaus and Efron Encyclopedic Dictionary : 86 t. (82 t. And 4 extra.). - SPb. , 1890-1907.
- Plant life : 6 tons / hl. ed. Al A. Fedorov . - M .: Enlightenment , 1978. - V. 4: Mosses. Moons Horsetails Ferns Gymnosperms / ed. I. V. Grushvitsky and S. G. Zhilin. - p. 131. - 447 p. - 300 000 copies
- Timonin A. K., Filin V. R. Kn. 1 // Systematics of higher plants: a textbook for students of higher educational institutions. In 2 books. - M .: Academy, 2009. - p. 226. - 320 p. - 2500 copies
Links
- Charcoal C. Appearance and evolution of horsetails . Postnauka publishing house (September 21, 2016). - Lecture. The appeal date is November 21, 2016.