| 单词 | tracheid |
| 例句 | The tissue consists of conducting cells, known as tracheids, and supportive filler tissue, called parenchyma. Fundamentals of Biology 2015-01-01T00:00:00Z Gymnosperm characteristics include naked seeds, separate female and male gametes, pollination by wind, and tracheids, which transport water and solutes in the vascular system. Concepts of Biology 2013-04-25T00:00:00Z Xylem tissue has three types of cells: xylem parenchyma, tracheids, and vessel elements. Biology for AP Courses 2022-06-09T00:00:00Z This colored scanning electron micrograph shows a bundle of tracheids in a softwood toothpick. Bundles of Plant-Water-Transportation Cells Resemble Snake Eyes 2020-10-09T04:00:00Z Instead of long, uninterrupted tubes, they are constructed of many short tubes called tracheids with angled ends. How a Tiny Pit Decides a Pine Tree’s Fate 2019-10-20T04:00:00Z Vessel elements are xylem cells with thinner walls; they are shorter than tracheids. Fundamentals of Biology 2015-01-01T00:00:00Z Gnetophyta are considered the closest group to angiosperms because they produce true xylem tissue that contains both tracheids and vessel elements. Concepts of Biology 2013-04-25T00:00:00Z This alternation of early and late wood is due largely to a seasonal decrease in the number of vessel elements and a seasonal increase in the number of tracheids. Biology for AP Courses 2022-06-09T00:00:00Z The xylem tissue of most gymnosperms comprises a single water-transporting cell type, tracheids. The Norway spruce genome sequence and conifer genome evolution 2013-05-29T17:21:22.577Z If during a drought air starts to creep into the tracheids from the roots, like a kid slurping up the dregs of a drink through a straw, the torus is pulled up against the aperture. How a Tiny Pit Decides a Pine Tree’s Fate 2019-10-20T04:00:00Z Xylem transports water and minerals through vessel elements and tracheids, which are dead at maturity and have a primary and secondary wall. Fundamentals of Biology 2015-01-01T00:00:00Z The wood of conifers is more primitive than the wood of angiosperms; it contains tracheids, but no vessel elements, and is referred to as “soft wood.” Concepts of Biology 2013-04-25T00:00:00Z The xylem consists of tracheids and vessels, which transport water and minerals to the leaves. Biology for AP Courses 2022-06-09T00:00:00Z The wood is characterized by the presence of vessels in addition to tracheids. Encyclopaedia Britannica, 11th Edition, Volume 12, Slice 7 "Gyantse" to "Hallel" 2011-12-26T03:00:11.613Z No other trait the scientists tested, such as wood density or tracheid diameter, affected growth rate or longevity. How a Tiny Pit Decides a Pine Tree’s Fate 2019-10-20T04:00:00Z The wood of conifers is more primitive than the wood of angiosperms; it contains tracheids, but no vessel elements, and is therefore referred to as “soft wood.” Fundamentals of Biology 2015-01-01T00:00:00Z Besides the tracheae and tracheids already noted are such cells as "wood fiber," "fibrous cells," and "parenchyma." Wood and Forest 2011-03-01T03:00:42.647Z The tracheids in the xylem contain mostly lipid droplets stained with Sudan Red. Biology for AP Courses 2022-06-09T00:00:00Z The secondary wood of Ephedra consists of tracheids, vessels and parenchyma; the vessels are characterized by their wide lumen and by the large simple or slightly-bordered pits on their oblique end-walls. Encyclopaedia Britannica, 11th Edition, Volume 12, Slice 7 "Gyantse" to "Hallel" 2011-12-26T03:00:11.613Z It is also possible that tracheid diameters and wood density are constrained by factors like freezing and dryness in a way that pits are not. How a Tiny Pit Decides a Pine Tree’s Fate 2019-10-20T04:00:00Z If the recent work on the cabbage disease may be accepted, the bacteria make their entry at the water pores at the margins of the leaf, and thence via the glandular cells to the tracheids. Encyclopaedia Britannica, 11th Edition, Volume 3, Part 1, Slice 2 "Baconthorpe" to "Bankruptcy" Spruce is hardly distinguishable from fir, except by the existence of the resin ducts, and microscopically by the presence of tracheids in the medullary rays. Wood and Forest 2011-03-01T03:00:42.647Z Water moves from one tracheid to another through regions on the side walls known as pits, where secondary walls are absent. Biology for AP Courses 2022-06-09T00:00:00Z The wood consists of tracheids, with circular bordered pits on their radial walls, and in the late summer wood pits are unusually abundant on the tangential walls. Encyclopaedia Britannica, 11th Edition, Volume 12, Slice 7 "Gyantse" to "Hallel" 2011-12-26T03:00:11.613Z Of other wood-characters, the presence or absence of tangential pits in the tracheids of the late wood establishes a distinction between Soft and Hard Pines. The Genus Pinus The softwoods are made up chiefly of tracheids, or vertical cells closed at the ends, and of the relatively short parenchyma cells of the medullary rays which extend radially from the heart of the tree. Seasoning of Wood Microscopically the white pine can be distinguished by having usually only one large pit, while spruce shows three to five very small pits in the parenchyma cells of the pith ray communicating with the tracheid. Wood and Forest 2011-03-01T03:00:42.647Z The xylem vessels and tracheids are structurally adapted to cope with large changes in pressure. Biology for AP Courses 2022-06-09T00:00:00Z When tracheids occur in the medullary rays of the xylem these are replaced in the phloem-region by irregular parenchymatous cells known as albuminous cells. Encyclopaedia Britannica, 11th Edition, Volume 12, Slice 7 "Gyantse" to "Hallel" 2011-12-26T03:00:11.613Z Walls of the tracheids of the medullary rays dentate. The Genus Pinus The course of the tracheids and the rays are at right angles to each other. Seasoning of Wood Walls of tracheids of pith ray smooth, without dentate projections. a. Wood and Forest 2011-03-01T03:00:42.647Z Water and minerals must cross the tracheids of the xylem. Biology for AP Courses 2022-06-09T00:00:00Z These empty cells are known as “tracheids,” and tissue composed of such empty cells, “tracheary tissue.” Elements of Structural and Systematic Botany For High Schools and Elementary College Courses These two are the only American Pines combining large pits with dentate tracheids, and are the only American Hard Pines with external resin-ducts of the leaf. The Genus Pinus Although the tracheids have their permeable portions or pits in their walls, liquids cannot pass through them with the greatest ease. Seasoning of Wood In 29 some, as ash, the tracheids are wanting; apple and maple have no woody fiber, and oak and plum no fibrous cells. Wood and Forest 2011-03-01T03:00:42.647Z As a rule buckling of a tracheid begins at the bordered pits which form places of least resistance in the walls. The Mechanical Properties of Wood Including a Discussion of the Factors Affecting the Mechanical Properties, and Methods of Timber Testing Besides the tracheids, there are a few small cells with oblique ends, and with some granular contents. Elements of Structural and Systematic Botany For High Schools and Elementary College Courses As shown in the figure, the tubes, cells or "tracheids" are decorated on their walls by circlet-like structures, the "bordered pits," sections of which are seen more magnified as a, b, and c, Fig. Seasoning of Wood They contain not only rays, and in many cases tracheids, but also thick-walled cells called fibres and wood parenchyma for the storage of such foods as starches and sugars. Seasoning of Wood These pits are in the nature of pores, covered by very thin membranes, and serve as waterways between the cells or tracheids. Seasoning of Wood If the force acts parallel to the axis of growth, the tracheids are more likely to be displaced if the marginal cells of the medullary rays are provided with weak walls that are readily compressed. The Mechanical Properties of Wood Including a Discussion of the Factors Affecting the Mechanical Properties, and Methods of Timber Testing B, part of the same, × 150. cam. cambium cells. x, tracheids. Elements of Structural and Systematic Botany For High Schools and Elementary College Courses The porous spring-wood and radial gray tracts are partly composed of smaller vessels, but chiefly of tracheids, like those of pine, and of shorter cells, the "wood parenchyma," resembling the cells of the medullary rays. Seasoning of Wood The vertical tubes are wood fibres, in this case all "tracheids." m, medullary or pith ray; n, transverse tracheids of ray; a, b, and c, bordered pits of the tracheids, more enlarged. Seasoning of Wood At y, the section has passed through the wall of a tracheid, bearing a row of pits, × 150. Elements of Structural and Systematic Botany For High Schools and Elementary College Courses The wood is mainly composed of tracheids, there being no vessels formed except the first year. Elements of Structural and Systematic Botany For High Schools and Elementary College Courses D, longitudinal section of a branch, showing the form of the tracheids and the bordered pits upon their walls. m, medullary ray, × 150. Elements of Structural and Systematic Botany For High Schools and Elementary College Courses These tracheids are characterized by the presence of peculiar pits upon their walls, best seen when thin longitudinal sections are made in a radial direction. Elements of Structural and Systematic Botany For High Schools and Elementary College Courses |
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