| 单词 | phloem |
| 例句 | All of its internal life exists within three paper-thin layers of tissue—the phloem, xylem, and cambium—just beneath the bark, which together form a moist sleeve around the dead heartwood. A Walk in the Woods 1997-11-01T00:00:00Z And lifting water is just one of the many jobs that the phloem, xylem, and cambium perform. A Walk in the Woods 1997-11-01T00:00:00Z Most sap-sucking insects drill into a nutrient-dense plant tissue called phloem, but spittlebugs specialize in the much more dilute sap from another tissue, xylem. Meet the world’s least picky insect—a spreader of deadly crop disease 2023-10-06T04:00:00Z Most sap-eating bugs feed from the plant's phloem, which is the tissue that transmits sugar and other metabolic compounds. Meadow Spittlebug's record-breaking diet also makes it top disease carrier for plants 2023-10-04T04:00:00Z Cells of the ground tissue are somewhat larger than phloem. Fundamentals of Biology 2015-01-01T00:00:00Z Xylem conducts water and minerals taken from the soil up to the shoot; phloem transports food derived from photosynthesis throughout the entire plant. Concepts of Biology 2013-04-25T00:00:00Z Dots inside that outline mark where the plant’s vascular tissues, the xylem and phloem, were connected, and conducted fluids between stem and leaf. How to read tree leaves — the science of plants 2022-12-02T05:00:00Z Internal vesicles called phloem carry sugar to fruits, and research indicates that pumpkins have more dedicated phloem tissue than most plants, helping them grow even larger. How to Grow a 2,560-Pound Pumpkin 2022-10-28T04:00:00Z Unlike sap from the phloem, the liquid in the xylem is similar across a diverse range of host plants. Meadow Spittlebug's record-breaking diet also makes it top disease carrier for plants 2023-10-04T04:00:00Z The stem is protected by an outer layer of dermal tissue, made up of several layers of cells smaller than phloem cells. Fundamentals of Biology 2015-01-01T00:00:00Z The vascular system contains xylem and phloem tissues. Concepts of Biology 2013-04-25T00:00:00Z Vascular tissue is an example of a complex tissue, and is made of two specialized conducting tissues: xylem and phloem. Biology for AP Courses 2022-06-09T00:00:00Z And giant pumpkins seem to have even more phloem tissue than smaller pumpkin varieties, Grumet adds. How to Grow a 2,560-Pound Pumpkin 2022-10-28T04:00:00Z Nutrient Transport The pressure-flow hypothesis states that sugars are transported through phloem via water pressure from osmosis to the places a plant needs it most. Miller & Levine Biology 2018-01-01T00:00:00Z The bundles are smaller than in the dicot stem, and distinct layers of xylem, phloem and sclerenchyma cannot be discerned. Fundamentals of Biology 2015-01-01T00:00:00Z A second type of vascular tissue is phloem, which transports sugars, proteins, and other solutes through the plant. Concepts of Biology 2013-04-25T00:00:00Z In stems, the xylem and the phloem form a structure called a vascular bundle; in roots, this is termed the vascular stele or vascular cylinder. Biology for AP Courses 2022-06-09T00:00:00Z In the flytrap, the phloem—the tissue that transports nutrients through a plant—contains ion channels through which charged particles can flow. Artificial Neuron Snaps a Venus Flytrap Shut 2022-03-01T05:00:00Z Xylem and phloem tissues pump themselves full of ions and organic compounds, which act like antifreeze to prevent tree sap from freezing. Miller & Levine Biology 2018-01-01T00:00:00Z Rows of green-staining phloem cells radiate out from the xylem cells. Fundamentals of Biology 2015-01-01T00:00:00Z Vascular systems consist of xylem tissue, which transports water and minerals, and phloem tissue, which transports sugars and proteins. Concepts of Biology 2013-04-25T00:00:00Z Phloem tissue is composed of sieve-tube cells, companion cells, phloem parenchyma, and phloem fibers. Biology for AP Courses 2022-06-09T00:00:00Z The insects specifically target and feed on nutrient-rich phloem sap from trees, which causes physical damage. The invasive spotted lantern fly is spreading across the Mid-Atlantic 2021-09-13T04:00:00Z Vascular plants also have a second transport tissue called phloem, which transports nutrients and carbohydrates produced by photosynthesis. Miller & Levine Biology 2018-01-01T00:00:00Z Outside the phloem is a ring of cells that make up the peripheral cortex. Fundamentals of Biology 2015-01-01T00:00:00Z Together, xylem and phloem tissues form the vascular system of plants. Concepts of Biology 2013-04-25T00:00:00Z The vascular cambium is located just outside the primary xylem and to the interior of the primary phloem. Biology for AP Courses 2022-06-09T00:00:00Z Most sap-drinking insects drink phloem, a sugary liquid in plant vessels that is easy to get because it is driven by positive pressure, meaning it gushes forth from a plant stem once pierced by mouthparts. This Insect Drinks Your Milkshake 2021-07-13T04:00:00Z The main cells of phloem are long and specialized to move fluids throughout the plant body. Miller & Levine Biology 2018-01-01T00:00:00Z Cells in the peripheral cortex are rounded rectangles that lie perpendicular to the phloem. Fundamentals of Biology 2015-01-01T00:00:00Z The simplest arrangement of conductive cells shows a pattern of xylem at the center surrounded by phloem. Concepts of Biology 2013-04-25T00:00:00Z This supplies oxygen to the living and metabolically active cells of the cortex, xylem and phloem. Biology for AP Courses 2022-06-09T00:00:00Z The xylem and phloem were not flowing properly. Yosemite's Sequoias have a vital message. Listen to them, urges Terry Tempest Williams 2019-10-07T04:00:00Z Vascular tissues—xylem and phloem—make it possible for vascular plants to move fluids through their bodies against the force of gravity. Miller & Levine Biology 2018-01-01T00:00:00Z The phloem is surrounded by a layer of sclerenchyma cells, then a layer of cortex cells. Fundamentals of Biology 2015-01-01T00:00:00Z But ultimately, they, too, succumb because of damage to two key tree components: vascular tissues called xylem and phloem. Why Amazon Trees Are Especially Vulnerable to This Year’s Fires 2019-09-13T04:00:00Z The phloem transports the photosynthetic products from the leaf to the other parts of the plant. Biology for AP Courses 2022-06-09T00:00:00Z Plant vascular tissue is comprised of water-transporting xylem cells and nutrient-transporting phloem cells, both of which are typically located in a central region of the mature root and stem. Plant-thickening mechanisms revealed 2019-01-08T05:00:00Z Tree sap, the sticky liquid from trees, is formed in the xylem and phloem. Miller & Levine Biology 2018-01-01T00:00:00Z Outside the xylem is a ring of phloem cells. Fundamentals of Biology 2015-01-01T00:00:00Z But the student was actually looking at normal phloem, a different network of vessels with a distinct structure that distributes nutrients formed in the leaves. The lost art of looking at plants 2018-01-22T05:00:00Z The products from the source are usually translocated to the nearest sink through the phloem. Biology for AP Courses 2022-06-09T00:00:00Z The division of cambial stem cells leads to the generation of xylem and phloem daughter cells towards the root interior and periphery, respectively. Plant-thickening mechanisms revealed 2019-01-08T05:00:00Z Based upon what you’ve learned about xylem and phloem, what do you think causes the sweet taste of maple syrup? Miller & Levine Biology 2018-01-01T00:00:00Z Small phloem cells make up the bottom of the bundle, and larger xylem cells make up the top. Fundamentals of Biology 2015-01-01T00:00:00Z The beetles chewed and fed on the tree’s phloem, conduits just below the bark for the tree’s life-giving juices. Farewell, giant pine: Climate change kills a champion at Washington Park Arboretum 2017-05-13T04:00:00Z Phloem STEs have reduced cytoplasmic contents, and are connected by a sieve plate with pores that allow for pressure- driven bulk flow, or translocation, of phloem sap. Biology for AP Courses 2022-06-09T00:00:00Z When the eggs hatch, the larvae feed off the phloem, draining the tree of its vital resources. Burning benefits 2016-05-19T04:00:00Z In monocots, clusters of xylem and phloem tissue, called vascular bundles, are scattered through stem ground tissue. Miller & Levine Biology 2018-01-01T00:00:00Z Outside the secondary xylem is a ring of secondary phloem tissue. Fundamentals of Biology 2015-01-01T00:00:00Z But the phloem is found in the tree, and is more rigid. Biologist Climbs High to Prove Hypothesis About Trees 2014-09-01T04:00:00Z Once in the phloem, the photosynthates are translocated to the closest sink. Biology for AP Courses 2022-06-09T00:00:00Z The beetles lay their eggs in the phloem layer inside the trees’ bark, which conducts nutrients from the leaves down to the roots. Burning benefits 2016-05-19T04:00:00Z Xylem and phloem cells are bundled in leaf veins. Miller & Levine Biology 2018-01-01T00:00:00Z The vascular cambium separates the xylem from the phloem. Fundamentals of Biology 2015-01-01T00:00:00Z There is no protection against the emerald ash borer, a green insect whose larvae eat phloem, the tissue layer that carries nutrients throughout a tree. Emerald ash borer could cost Lincoln $23 million 2014-08-03T04:00:00Z The high percentage of sugar decreases Ψs, which decreases the total water potential and causes water to move by osmosis from the adjacent xylem into the phloem tubes, thereby increasing pressure. Biology for AP Courses 2022-06-09T00:00:00Z Tissues generally referred to as phloem move such water-soluble nutrients throughout the plant. Poison Pen: The Trouble With Rice 2014-04-18T20:43:07Z For example, aphids can flourish during short droughts as plant nutrients become more concentrated, but these benefits cease during prolonged droughts because of a drop in fluid pressure within the phloem of water-stressed plants. Crop pests: Under attack 2013-09-25T21:50:48.970Z Bundles of primary phloem project outward from the secondary phloem into the cortex. Fundamentals of Biology 2015-01-01T00:00:00Z A second set of channels, the phloem, found just under a tree’s bark, carries the products of photosynthesis to the roots. Dendrochronology: Not always the ring of truth 2013-06-20T15:05:37Z Unloading at the sink end of the phloem tube occurs by either diffusion or active transport of sucrose molecules from an area of high concentration to one of low concentration. Biology for AP Courses 2022-06-09T00:00:00Z And if a leaf is shorter than a certain minimum length, then the sap would flow through the phloem more slowly than it could simply diffuse through the tree. Simple Physics May Limit the Size of Leaves 2013-01-04T17:10:00Z The bacteria attack the trees’ phloem, or vascular tissue, preventing the transport of nutrients. Green Blog: Blight Threatens California's Citrus Trees 2012-04-17T18:14:55Z Xylem conducts water and minerals absorbed from the soil up to the shoot, while phloem transports food derived from photosynthesis throughout the entire plant. Fundamentals of Biology 2015-01-01T00:00:00Z Mercury is carried there by the phloem and selectively deposited in it, rather than in the plants’ more permanent parts. Dendrochronology: Not always the ring of truth 2013-06-20T15:05:37Z This reduces the water potential, which causes water to enter the phloem from the xylem. Biology for AP Courses 2022-06-09T00:00:00Z Sap diffuses into the leaf phloem and travels down the trunk phloem. Simple Physics May Limit the Size of Leaves 2013-01-04T17:10:00Z They are explained as due to the borings of minute insects, Diptera or Beetles, the larvae of which pierce the cortex and phloem and bore their way into the cambium. Disease in Plants 2012-03-01T03:00:22Z Apical meristems differentiate into the three basic types of meristem tissue which correspond to the three types of tissue: protoderm produces new epidermis, ground meristem produces ground tissue, and procambium produces new xylem and phloem. Fundamentals of Biology 2015-01-01T00:00:00Z The tissue in question is marked by S, c, hb in the figure, and is called phloem or bast. Scientific American Supplement, No. 648, June 2, 1888. 2011-12-26T03:00:15.410Z Vascular tissue, for example, is made up of xylem and phloem cells. Biology for AP Courses 2022-06-09T00:00:00Z At that point, the phloem plumbing would become useless. Simple Physics May Limit the Size of Leaves 2013-01-04T17:10:00Z Finally, in the pinnae of the frond the centrifugal xylem may disappear, the protoxylem being now exarch in position and abutting on the phloem. Encyclopaedia Britannica, 11th Edition, Volume 12, Slice 7 "Gyantse" to "Hallel" 2011-12-26T03:00:11.613Z Cork cambiumlies between the epidermis and the phloem, and replaces the epidermis of roots and stems with bark, one layer of which is cork. Fundamentals of Biology 2015-01-01T00:00:00Z So do the blood vessels of animals and the sap-carrying xylem and phloem of plants. 2010-02-11T10:38:00Z Sucrose is actively loaded into the sieve-tube elements of the phloem. Biology for AP Courses 2022-06-09T00:00:00Z For example, he says, there is not a one-to-one relationship between leaves and phloem tubes in the trunk, as the tubes merge. Simple Physics May Limit the Size of Leaves 2013-01-04T17:10:00Z The phloem consists of sieve-tubes, with pitted areas on the lateral as well as on the inclined terminal walls, phloem-parenchyma and, in some genera, fibres. Encyclopaedia Britannica, 11th Edition, Volume 12, Slice 7 "Gyantse" to "Hallel" 2011-12-26T03:00:11.613Z Attached to the vascular cambium are primary phloem and primary xylem. Fundamentals of Biology 2015-01-01T00:00:00Z Unlike the xylem and phloem, the veins in a leaf cross-link and loop. 2010-02-11T10:38:00Z The sieve elements in the phloem show staining with Sudan Red because of transported oil droplets. Biology for AP Courses 2022-06-09T00:00:00Z A leaf of an angiosperm produces a sugary sap that flows into a network of pipelike cells called the phloem, which transports the sap down the tree's trunk and through the roots. Simple Physics May Limit the Size of Leaves 2013-01-04T17:10:00Z Resin-canals, which occur abundantly in the xylem, phloem or cortex, are not found in the wood of the yew. Encyclopaedia Britannica, 11th Edition, Volume 12, Slice 7 "Gyantse" to "Hallel" 2011-12-26T03:00:11.613Z The carbohydrates are exported to the rest of the plant by the conductive cells of phloem tissue. Fundamentals of Biology 2015-01-01T00:00:00Z The browning in the vascular bundles appeared to be confined to the phloem tissue. Northern Nut Growers Association Thirty-Fourth Annual Report 1943 Unlike xylem conducting cells, phloem conducting cells are alive at maturity. Biology for AP Courses 2022-06-09T00:00:00Z Things are different in the trunk phloem: There, the longer the tube is, the more frictionlike resistance it offers to flow. Simple Physics May Limit the Size of Leaves 2013-01-04T17:10:00Z The outer limits of the bundles are not nearly so distinct, and it is not easy to tell when the phloem of the bundles ends and the ground tissue of the bark begins. Elements of Structural and Systematic Botany For High Schools and Elementary College Courses A single unbranched vein—a bundle of vascular tissue made of xylem and phloem—runs through the center of the leaf. Fundamentals of Biology 2015-01-01T00:00:00Z The vascular bundles of the stem belong to the collateral type, that is to say, the elements of the wood or xylem and the bast or phloem stand side by side on the same radius. Encyclopaedia Britannica, 11th Edition, Volume 2, Part 1, Slice 1 In dicot roots, the xylem and phloem of the stele are arranged alternately in an X shape, whereas in monocot roots, the vascular tissue is arranged in a ring around the pith. Biology for AP Courses 2022-06-09T00:00:00Z The pericycle is a ring of cells on the outer edge of the xylem and phloem. Fundamentals of Biology 2015-01-01T00:00:00Z The phloem, when strongly magnified, is seen to be made up of cells arranged in nearly regular radiating rows. Elements of Structural and Systematic Botany For High Schools and Elementary College Courses To the outside of the xylem vessels are much smaller phloem cells. Fundamentals of Biology 2015-01-01T00:00:00Z The soft phloem soon becomes crushed, but the hard wood persists, and forms the great bulk of the stem and branches of the woody perennial. Encyclopaedia Britannica, 11th Edition, Volume 2, Part 1, Slice 1 A single vascular bundle, no matter how large or small, always contains both xylem and phloem tissues. Biology for AP Courses 2022-06-09T00:00:00Z Round clusters of xylem cells are embedded in the phloem, symmetrically arranged around the central pith. Fundamentals of Biology 2015-01-01T00:00:00Z There is a ring of small cambium cells around this merging into the phloem, which is composed of irregular cells, with pretty thick, but soft walls. Elements of Structural and Systematic Botany For High Schools and Elementary College Courses Lateral sieve areas on the side of the column allow different phloem tubes to interact.Part b shows the transpiration of water up the tubes of the xylem from a root sink cell. Fundamentals of Biology 2015-01-01T00:00:00Z Phloem STEs have reduced cytoplasmic contents, and are connected by a sieve plate with pores that allow for pressure-driven bulk flow, or translocation, of phloem sap. Fundamentals of Biology 2015-01-01T00:00:00Z Vascular tissue is made up of xylem and phloem tissues and conducts water, minerals, and photosynthetic products. Biology for AP Courses 2022-06-09T00:00:00Z Xylem is located toward the inside of the vascular bundle, and phloem is in the middle. Fundamentals of Biology 2015-01-01T00:00:00Z The rest of the phloem is composed of very small cells. Elements of Structural and Systematic Botany For High Schools and Elementary College Courses At the same time, sucrose is translocated down the phloem to the root sink cell from a leaf source cell. Fundamentals of Biology 2015-01-01T00:00:00Z Outside the secondary phloem is the cortex layer. Fundamentals of Biology 2015-01-01T00:00:00Z The increased solute concentration causes water to move by osmosis from the xylem into the phloem. Biology for AP Courses 2022-06-09T00:00:00Z Carbohydrates synthesized in photosynthesis, primarily sucrose, move from sources to sinks through the plant’s phloem. Biology for AP Courses 2022-06-09T00:00:00Z The wood is distinguished by the presence of vessels with close, spiral or ring-shaped thickenings, while in the phloem are found sieve tubes, not unlike those in the ferns. Elements of Structural and Systematic Botany For High Schools and Elementary College Courses Phloem cells fill the space between the X. A ring of cells called the pericycle surrounds the xylem and phloem. Fundamentals of Biology 2015-01-01T00:00:00Z Sucrose produced in the Calvin cycle is loaded into the sieve-tube elements of the phloem, and the increased solute concentration causes water to move by osmosis from the xylem into the phloem. Biology for AP Courses 2022-06-09T00:00:00Z Xylem tissue would show the presence of labeled minerals and phloem tissue would show the presence of radioactive sucrose. Biology for AP Courses 2022-06-09T00:00:00Z The phloem and xylem are the main tissues responsible for this movement. Biology for AP Courses 2022-06-09T00:00:00Z The xylem, as in the pine, is toward the outside of the stem, but the boundary between xylem and phloem is not well defined, there being no cambium present. Elements of Structural and Systematic Botany For High Schools and Elementary College Courses The phloem cells form a ring around the pith. Fundamentals of Biology 2015-01-01T00:00:00Z Sugars produced in sources, such as leaves, need to be delivered to growing parts of the plant via the phloem in a process called translocation. Biology for AP Courses 2022-06-09T00:00:00Z In dicots, the phloem and xylem cells are scattered in the pith. Biology for AP Courses 2022-06-09T00:00:00Z From there they are translocated through the phloem to where they are used or stored. Biology for AP Courses 2022-06-09T00:00:00Z The rest of the xylem cells, as well as those of the phloem, are not noticeably different from the cells of the ground tissue, except for their much smaller size, and absence of intercellular spaces. Elements of Structural and Systematic Botany For High Schools and Elementary College Courses A cross section at the top of the root reveals xylem tissue interspersed by four ovals containing phloem at the periphery. Fundamentals of Biology 2015-01-01T00:00:00Z Water diffuses from the phloem by osmosis and is then transpired or recycled via the xylem back into the phloem sap. Biology for AP Courses 2022-06-09T00:00:00Z The physical separation of xylem and phloem permits plants to move different nutrients simultaneously from roots to shoots and vice versa. Biology for AP Courses 2022-06-09T00:00:00Z The vascular bundles divide into primary xylem and primary phloem. Biology for AP Courses 2022-06-09T00:00:00Z The vascular bundles divide into secondary xylem and primary phloem. Biology for AP Courses 2022-06-09T00:00:00Z Patches of phloem cells, stained blue, are located at the edge of the ring of xylem cells. Fundamentals of Biology 2015-01-01T00:00:00Z |
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