Chapter 23 Plant Structure and Function 1.Tissue systems and growing regions 2.Roots 3.Stems 4.Leaves.

Chapter 23Chapter 23Plant Structure Plant Structure and Functionand Function

1.1. Tissue systems and growing regionsTissue systems and growing regions

2.2. RootsRoots

3.3. StemsStems

4.4. LeavesLeaves

Tissue SystemsTissue Systems

Ground systemGround system Vascular systemVascular system

Dermal tissue systemDermal tissue system

Vascular and Dermal Vascular and Dermal SystemsSystems VascularVascular

Xylem conducts water and mineralsXylem conducts water and minerals Phloem conducts foodPhloem conducts food

DermalDermal Epidermis: outer layer of cellsEpidermis: outer layer of cells

Ground SystemGround System Parenchyma Parenchyma

tissue: food tissue: food storagestorage

Collenchyma Collenchyma tissue: growing tissue: growing regions of the regions of the plantplant

Sclerenchyma: at Sclerenchyma: at maturity is made maturity is made of dead cells that of dead cells that support and support and strengthen the strengthen the plantplant

Meristems: growing Meristems: growing regions where cells regions where cells dividedivide Apical Meristem: the tips of stems and roots (result Apical Meristem: the tips of stems and roots (result of primary growth)of primary growth)

Lateral meristem: the circumference grows (result of Lateral meristem: the circumference grows (result of secondary growth)secondary growth) Cork cambium and vascular cambiumCork cambium and vascular cambium

Herbaceous Plants have no vascular cambium so Herbaceous Plants have no vascular cambium so are nonwoodyare nonwoody

Woody Plants are perennial (adapted for growth Woody Plants are perennial (adapted for growth year after year) so they produce secondary xylem.year after year) so they produce secondary xylem.

Roots: StructureRoots: Structure

Root tip – 3 regionsRoot tip – 3 regions Region of cell divisionRegion of cell division Region of elongationRegion of elongation Region of maturation

Root cap: composed of Root cap: composed of cells that protect the cells that protect the apical meristemapical meristem

Roots: primary Roots: primary growthgrowth Root hairs Root hairs

increase surface increase surface area for area for absorptionabsorption

Cortex: storage Cortex: storage tissue for the tissue for the young rootyoung root

Vascular cylinder: Vascular cylinder: contains xylem contains xylem and phloemand phloem

Roots: secondary growthRoots: secondary growth Occurs when a Occurs when a

vascular cambium vascular cambium forms between forms between the primary xylem the primary xylem and phloem.and phloem.

Provides strength Provides strength and support for and support for the plant stem.the plant stem.

Roots: FunctionsRoots: Functions

Absorption of water and inorganic Absorption of water and inorganic nutrientsnutrients The amount of water absorbed depends on The amount of water absorbed depends on

the amount lost through transpiration which the amount lost through transpiration which is the evaporation of water from stems and is the evaporation of water from stems and leaves.leaves.

Food storageFood storage Anchors the plantAnchors the plant

Stems: Structure Primary GrowthStems: Structure Primary Growth Stems only grow at the apical meristemStems only grow at the apical meristem Dermal tissue protects the stemDermal tissue protects the stem Ground tissue forms a cortex and a pith (in Ground tissue forms a cortex and a pith (in

gymnosperms and dicots)gymnosperms and dicots) Vascular bundles: xylem and phloemVascular bundles: xylem and phloem

Monocots: bundles are scattered throughout Monocots: bundles are scattered throughout ground tissueground tissue

Dicots: bundles occur in a single ringDicots: bundles occur in a single ring

Stems: secondary growthStems: secondary growth Stems increase in thickness due to cell division Stems increase in thickness due to cell division

in the vascular cambium (production of more in the vascular cambium (production of more secondary xylem is wood).secondary xylem is wood).

Rays are sheets of cells that radiate from the Rays are sheets of cells that radiate from the stem center storing food and transporting water stem center storing food and transporting water laterally across the xylemlaterally across the xylem

Annual rings develop because of water Annual rings develop because of water differences among seasonsdifferences among seasons

Bark is the outer layers that protect a plant and Bark is the outer layers that protect a plant and consists of cork, cork cambium, cortex and consists of cork, cork cambium, cortex and secondary phloem.secondary phloem.

Secondary Growth in Secondary Growth in StemStem

Stems: FunctionsStems: Functions SupportSupport Food Transport:Food Transport:

Food: sugar moves from source to sinkFood: sugar moves from source to sink Pressure-flow hypothesis (diffusion) explains thisPressure-flow hypothesis (diffusion) explains this

Water Transport:Water Transport: Transpiration-cohesion theory – osmosis and cohesionTranspiration-cohesion theory – osmosis and cohesion

StorageStorage PhotosynthesisPhotosynthesis

Leaves: StructureLeaves: Structure Leaves are the result of only primary Leaves are the result of only primary

growthgrowth Parts: blade and petioleParts: blade and petiole

Leaves: internal Leaves: internal structurestructure

Epidermis: impermeable layer that only allows Epidermis: impermeable layer that only allows water, oxygen and carbon dioxide to passwater, oxygen and carbon dioxide to pass

Mesophyll: chloroplast-rich parenchyma cellsMesophyll: chloroplast-rich parenchyma cells Palisade mesophyll lies directly below the Palisade mesophyll lies directly below the

epidermisepidermis Spongy mesophyll lies between the palisade and Spongy mesophyll lies between the palisade and

lower epidermislower epidermis

Vascular tissue is contained in veins Vascular tissue is contained in veins surrounded by bundle sheaths.surrounded by bundle sheaths.

Leaf cross section:Leaf cross section:

Leaves: FunctionsLeaves: Functions

Capturing lightCapturing light Gas exchange: Gas exchange:

Guard cells surrounding openings called stomataGuard cells surrounding openings called stomata Opening and closing regulated by turgor pressureOpening and closing regulated by turgor pressure

1)When guard cells have water – guard cells expand and 1)When guard cells have water – guard cells expand and create a porecreate a pore

2) When guard cells have lost water, they shrink and close the 2) When guard cells have lost water, they shrink and close the porepore