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StemsStems3 Functions:3 Functions:
Support leaves Support leaves and reproductive and reproductive structuresstructures
Internal transportInternal transport
Produce new Produce new tissuetissue
External StucturesExternal Stuctures
Internal Structures: Internal Structures: MonocotsMonocots
Most herbaceousMost herbaceous Exception: PalmsException: Palms
Vascular bundles Vascular bundles
Ground tissueGround tissue
No lateral No lateral meristemsmeristems
Internal Structures: Internal Structures: Herbaceous DicotsHerbaceous Dicots
CortexCortex
Vascular tissueVascular tissue Some have Some have
vascular vascular cambiumcambium
Annual vs. Annual vs. PerrenialPerrenial
PithPith
Woody Stems of EudicotsWoody Stems of Eudicots
Primary tissue arranged like that in Primary tissue arranged like that in herbaceous stemherbaceous stem
Secondary growth Secondary growth GirthGirth Vascular cambiumVascular cambium Cork cambiumCork cambium
Once secondary growth begins, internal Once secondary growth begins, internal structure changes structure changes
Secondary GrowthSecondary Growth
Vascular cambium Vascular cambium become continuousbecome continuous
Cells in cambium Cells in cambium produce daughter cells produce daughter cells in 2 directionsin 2 directions
After division, 1 cell After division, 1 cell remains meristematicremains meristematic
As secondary tissue forms 1As secondary tissue forms 1o o xylem and xylem and phloem become separated from each phloem become separated from each otherother
11oo tissue outside cylinder of growth tissue outside cylinder of growth crushed or torn apartcrushed or torn apart
22oo xylem and phloem contain same types xylem and phloem contain same types of cells and perform same function as of cells and perform same function as primary tissueprimary tissue
Rays connect 2Rays connect 2oo xylem and phloem and xylem and phloem and allow for lateral transport of materialallow for lateral transport of material
Cork CambiumCork Cambium
Arises from parenchyma cells in outer Arises from parenchyma cells in outer cortexcortex
Produces peridermProduces periderm
Cork cells form to the outsideCork cells form to the outside Dead at maturityDead at maturity Waterproof & Impermeable to gasesWaterproof & Impermeable to gases
Cork parechyma form to insideCork parechyma form to inside
Common Wood TermsCommon Wood Terms SoftwoodSoftwood
HardwoodHardwood
Sapwood Sapwood
Heartwood – Older wood, in centerHeartwood – Older wood, in center
Annual RingsAnnual Rings
Used to determine the age of a tree Used to determine the age of a tree in temperate climatein temperate climate
Difference between springwood and Difference between springwood and summerwoodsummerwood Springwood – large diameter of Springwood – large diameter of
conducting cells, few fibersconducting cells, few fibers Summerwood – narrower conducting Summerwood – narrower conducting
cells, more fiberscells, more fibers