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Leptoids
A leptoid is a type of elongated food-conducting cell like phloem in the stems of some mosses, such as the family Polytrichaceae. They surround strands of water-conducting hydroids. They have some structural and developmental similarities to the sieve elements of seedless vascular plants Vascular plants (), also called tracheophytes () or collectively Tracheophyta (), form a large group of land plants ( accepted known species) that have lignified tissues (the xylem) for conducting water and minerals throughout the plant. They al .... At maturity they have inclined end cell walls with small pores and degenerate nuclei. The conduction cells of mosses, leptoids and hydroids, appear similar to those of fossil protracheophytes. However they're not thought to represent an intermediate stage in the evolution of plant vascular tissues but to have had an independent evolutionary origin.Renzaglia, K.S., Schette, S. and Duff, R.J. (2007) Bryophyte phylogeny: advancing the molecular and mo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phloem
Phloem (, ) is the living biological tissue, tissue in vascular plants that transports the soluble organic compounds made during photosynthesis and known as ''photosynthates'', in particular the sugar sucrose, to the rest of the plant. This transport process is called translocation. In trees, the phloem is the innermost layer of the bark (botany), bark, hence the name, derived from the Ancient Greek word (''phloiós''), meaning "bark". The term was introduced by Carl Nägeli in 1858. Structure Phloem tissue consists of conducting Cell (biology), cells, generally called sieve elements, Ground tissue#Parenchyma, parenchyma cells, including both specialized companion cells or albuminous cells and unspecialized cells and supportive cells, such as fibres and sclereids. Conducting cells (sieve elements) Sieve elements are the type of cell that are responsible for transporting sugars throughout the plant. At maturity they lack a Cell nucleus, nucleus and have very few organelles, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Moss
Mosses are small, non-vascular flowerless plants in the taxonomic division Bryophyta (, ) '' sensu stricto''. Bryophyta (''sensu lato'', Schimp. 1879) may also refer to the parent group bryophytes, which comprise liverworts, mosses, and hornworts. Mosses typically form dense green clumps or mats, often in damp or shady locations. The individual plants are usually composed of simple leaves that are generally only one cell thick, attached to a stem that may be branched or unbranched and has only a limited role in conducting water and nutrients. Although some species have conducting tissues, these are generally poorly developed and structurally different from similar tissue found in vascular plants. Mosses do not have seeds and after fertilisation develop sporophytes with unbranched stalks topped with single capsules containing spores. They are typically tall, though some species are much larger. ''Dawsonia'', the tallest moss in the world, can grow to in height. There are a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polytrichaceae
Polytrichaceae is a common family of mosses. Members of this family tend to be larger than other mosses with a thickened central stem and a rhizome. The leaves have a midrib that bears photosynthetic lamellae on the upper surface. Species in this group are dioicous. Another characteristic that identifies them is that they have from 32 to 64 peristome teeth in their sporangium. Classification Genera Extinct genera * '' Eopolytrichum'' Konopka, Herendeen, Merrill & Crane (1997), Gaillard Formation, Georgia, USA, Upper Cretaceous (Campanian) * '' Meantoinea'' Bippus, Stockey, Rothwell & Tomescu (2017) Apple Bay locality, Vancouver Island, Canada, Lower Cretaceous (Valanginian In the geologic timescale, the Valanginian is an age or stage of the Early or Lower Cretaceous. It spans between 139.8 ± 3.0 Ma and 132.9 ± 2.0 Ma (million years ago). The Valanginian Stage succeeds the Berriasian Stage of the Lower Cretace ...) References Moss families [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hydroid (botany)
A hydroid is a type of vascular cell that occurs in certain bryophytes. In some mosses such as members of the Polytrichaceae family, hydroids form the innermost layer of cells in the stem. At maturity they are long, colourless, thin walled cells of small diameter, containing water but no living protoplasm. Collectively, hydroids function as a conducting tissue, known as the hydrome, transporting water and minerals drawn from the soil. They are surrounded by bundles of living cells known as leptoids which carry sugars and other nutrients in solution. The hydroids are analogous to the tracheids of vascular plants but there is no lignin present in the cell walls to provide structural support. Hydroids have been found in some fossilised plants from the Rhynie chert, including ''Aglaophyton'', where they were initially mistaken for xylem tracheids. See also *Leptoid, a related sucrose-transporting vessel analogous to the phloem Phloem (, ) is the living biological tissue, tissue in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sieve Element
Sieve elements are specialized cells that are important for the function of phloem, which is a highly organized tissue that transports organic compounds made during photosynthesis. Sieve elements are the major conducting cells in phloem. Conducting cells aid in transport of molecules especially for long-distance signaling. In plant anatomy, there are two main types of sieve elements. Companion cells and sieve cells originate from meristems, which are tissues that actively divide throughout a plant's lifetime. They are similar to the development of xylem, a water conducting tissue in plants whose main function is also transportation in the plant vascular system. Sieve elements' major function includes transporting sugars over long distance through plants by acting as a channel. Sieve elements elongate cells containing sieve areas on their walls. Pores on sieve areas allow for cytoplasmic connections to neighboring cells, which allows for the movement of photosynthetic material and ot ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vascular Plants
Vascular plants (), also called tracheophytes () or collectively Tracheophyta (), form a large group of land plants ( accepted known species) that have lignified tissues (the xylem) for conducting water and minerals throughout the plant. They also have a specialized non-lignified tissue (the phloem) to conduct products of photosynthesis. Vascular plants include the clubmosses, horsetails, ferns, gymnosperms (including conifers), and angiosperms (flowering plants). Scientific names for the group include Tracheophyta, Tracheobionta and Equisetopsida ''sensu lato''. Some early land plants (the rhyniophytes) had less developed vascular tissue; the term eutracheophyte has been used for all other vascular plants, including all living ones. Historically, vascular plants were known as "higher plants", as it was believed that they were further evolved than other plants due to being more complex organisms. However, this is an antiquated remnant of the obsolete scala naturae, and the term ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hydroid (botany)
A hydroid is a type of vascular cell that occurs in certain bryophytes. In some mosses such as members of the Polytrichaceae family, hydroids form the innermost layer of cells in the stem. At maturity they are long, colourless, thin walled cells of small diameter, containing water but no living protoplasm. Collectively, hydroids function as a conducting tissue, known as the hydrome, transporting water and minerals drawn from the soil. They are surrounded by bundles of living cells known as leptoids which carry sugars and other nutrients in solution. The hydroids are analogous to the tracheids of vascular plants but there is no lignin present in the cell walls to provide structural support. Hydroids have been found in some fossilised plants from the Rhynie chert, including ''Aglaophyton'', where they were initially mistaken for xylem tracheids. See also *Leptoid, a related sucrose-transporting vessel analogous to the phloem Phloem (, ) is the living biological tissue, tissue in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Xylem
Xylem is one of the two types of transport tissue in vascular plants, the other being phloem. The basic function of xylem is to transport water from roots to stems and leaves, but it also transports nutrients. The word ''xylem'' is derived from the Ancient Greek word (''xylon''), meaning "wood"; the best-known xylem tissue is wood, though it is found throughout a plant. The term was introduced by Carl Nägeli in 1858. Structure The most distinctive xylem cells are the long tracheary elements that transport water. Tracheids and vessel elements are distinguished by their shape; vessel elements are shorter, and are connected together into long tubes that are called ''vessels''. Xylem also contains two other type of cells: parenchyma and fibers. Xylem can be found: * in vascular bundles, present in non-woody plants and non-woody parts of woody plants * in secondary xylem, laid down by a meristem called the vascular cambium in woody plants * as part of a stelar arrangement n ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mosses
Mosses are small, non-vascular flowerless plants in the taxonomic division Bryophyta (, ) ''sensu stricto''. Bryophyta (''sensu lato'', Schimp. 1879) may also refer to the parent group bryophytes, which comprise liverworts, mosses, and hornworts. Mosses typically form dense green clumps or mats, often in damp or shady locations. The individual plants are usually composed of simple leaves that are generally only one cell thick, attached to a stem that may be branched or unbranched and has only a limited role in conducting water and nutrients. Although some species have conducting tissues, these are generally poorly developed and structurally different from similar tissue found in vascular plants. Mosses do not have seeds and after fertilisation develop sporophytes with unbranched stalks topped with single capsules containing spores. They are typically tall, though some species are much larger. ''Dawsonia'', the tallest moss in the world, can grow to in height. There are app ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
