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Download 22.1 Plant Cells and Tissues
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22.1PlantCellsandTissues PlantCells § Differentkindsofplantcellsmakeupplanttissues. ParenchymaCells § Mostflexible,thin-walledcellsfoundthroughoutthe plantareparenchymacells. § Functions: § Storage § Photosynthesis § Gasexchange § Protection § Tissuerepairandreplacement CollenchymaCells § Plantcellsthatoftenareelongatedand occurinlongstrandsorcylindersthat providesupportforthesurroundingcells arecollenchymacells. § Functions: § Supportforsurroundingtissues § Providesflexibilityforplant § Tissuerepairandreplacement SclerenchymaCells § Plantcellsthatlackcytoplasmandotherlivingcomponentswhentheymature,leaving thick,rigidcellwallsarecalledsclerenchymacells. § Functions: § Support § Transportofmaterials PlantTissues § Aplanttissuecanbecomposedofoneormoretypesofcells. § Therearefourdifferenttissuetypesfoundinplants—meristematic,dermal,vascular, andground. MeristematicTissue § Meristematictissuesmakeup meristems,orregionsofrapidly dividingcells. § Apicalmeristemsincreaselength § Lateralmeristemsincreasegirth DermalTissue § Thelayerofcellsthatmakesupthe outercoveringonaplantisthe epidermis. § Mostepidermalcellscancreateafattysubstancethatformsthecuticle. § Thecuticlehelpsreducewaterlossandpreventbacteriafromenteringtheplant. Stomata § Smallopeningsthroughwhichcarbondioxide,water,oxygen,andothergasespass § Thetwocellsthatborderastomaareguardcells. Trichomes § Hairlikeprojectionsthatprotecttheplant RootHairs § Increasearoot’ssurfaceareaandenabletheroottotakeinagreatervolumeof materials VascularTissue Xylem § Transportssubstancesaway fromtheroots § Composedofspecializedcells calledvesselelementsand tracheids § Vesselelementsaretubular cellsstackedend-to-endthat enablethefreemovementof wateranddissolved substances. § Tracheidsarelong,cylindrical cellswithpittedendsthat allowmovementofwaterand dissolvedsubstances. § § § § § Becausematuretracheidshaveendwalls,theyarelessefficientthanvesselelements. Waterentersthexylemintheroots Inthexylemthewatermoleculesformhydrogenbonds,linkingtogetherinacontinuous stringuptotheleaf Waterisconstantlylostbytranspirationintheleaf § Whenonewatermoleculeislostanotherispulled along Xylemflowsup:“Rootstoshoots” Phloem § Transportsdissolvedsugarsandotherorganiccompounds throughouttheplant. § Cantransportfromleavesdown: “Shootstoroots” § Composedof: § Sieve-tubemember § Companioncells GroundTissue § Consistofparenchyma,collenchyma,andsclerenchymacells § Functionsincludephotosynthesis,storage,andsupport
