Chapter #35~ Chapter #35~ Plant Structure and Plant Structure and GrowthGrowth

AngiospermsAngiosperms

Flowering PlantsFlowering Plants

– Two ClassesTwo Classes

Monocots- named for single Monocots- named for single cotyledoncotyledon

Dicots- named for two cotyledonsDicots- named for two cotyledons

– See structural differences (35.3)See structural differences (35.3)

Angiosperm structureAngiosperm structureTwo Main Systems- 3 basic organsTwo Main Systems- 3 basic organs– Root SystemRoot System– Shoot SystemShoot System

Stems and leavesStems and leaves

Each system depends upon one anotherEach system depends upon one another– Root system needs organic nutrients from the shoot Root system needs organic nutrients from the shoot

systemsystem– Shoot system needs water and minerals absorbed by root Shoot system needs water and minerals absorbed by root

system system

How does the Root and Shoot system exchange materials?How does the Root and Shoot system exchange materials?– Vascular tissueVascular tissue

Xylem- waterXylem- water

Phloem - FoodPhloem - Food

Root SystemRoot SystemRoots anchor plant and absorb minerals and waterRoots anchor plant and absorb minerals and water

Two typesTwo types

fibrous: mat of thin roots ( threadlike)fibrous: mat of thin roots ( threadlike)– Grasses and many monocots have these Grasses and many monocots have these – Roots are usually concentrated in the upper few Roots are usually concentrated in the upper few

centimeters of soil- help with erosion centimeters of soil- help with erosion

taproot: one large, vertical root with many smaller taproot: one large, vertical root with many smaller lateral rootslateral roots

– Most dicots have theseMost dicots have these

Root hairs- increase surface area and help with Root hairs- increase surface area and help with absorptionabsorption

Fig. 35-4

Prop roots

“Strangling”aerial roots

Storage roots

Buttress roots

Pneumatophores

Shoot SystemsShoot SystemsStemsStems (shoot system) (shoot system) – nodes: leave attachment nodes: leave attachment – internodes: stem segments internodes: stem segments – axillary bud: dormant, vegetative potential axillary bud: dormant, vegetative potential

– terminal bud: apex of young shoot terminal bud: apex of young shoot – apical dominance: inhibits axillary budsapical dominance: inhibits axillary budsLeavesLeaves (shoot system) (shoot system)– bladeblade– PetiolePetiole– Monocots have parallel veins and dicots have Monocots have parallel veins and dicots have

branched veinbranched vein

Fig. 35-5Rhizomes

Bulbs

Storage leaves

Stem

Stolons

Stolon

Tubers

Fig. 35-6

( Simple leaf

Compoundleaf

(b)

Doublycompoundleaf

(c)

Petiole

Axillary bud

PetioleAxillary bud

LeafletPetioleAxillary bud

Fig. 35-7Tendrils

Spines

Storageleaves

Reproductive leaves

Bracts

Types of Plant TissuesTypes of Plant TissuesDermalDermal (epidermis): single layer of cells for protection (epidermis): single layer of cells for protection cuticlecuticle

Vascular Vascular (material transport)(material transport)– xylem: water and dissolved minerals roots to shootsxylem: water and dissolved minerals roots to shoots

tracheids & vessel elements: xylem elongated tracheids & vessel elements: xylem elongated cells dead at maturitycells dead at maturity

– phloem: food from leaves to roots and fruitsphloem: food from leaves to roots and fruits

sieve-tube members: phloem tubes alive at sieve-tube members: phloem tubes alive at maturity capped by sieve plates; companion cells maturity capped by sieve plates; companion cells (non-conducting) connected by plasmodesmata(non-conducting) connected by plasmodesmata

Ground Ground (photosynthesis, storage, support): pith and (photosynthesis, storage, support): pith and cortexcortex

Plant Tissue Cell Types Within Plant Tissue Cell Types Within TissuesTissuesParenchymaParenchyma

– primary walls thin and flexibleprimary walls thin and flexible– no secondary wallsno secondary walls– large central vacuolelarge central vacuole– most metabolic functions of plant (chloroplasts)most metabolic functions of plant (chloroplasts)

CollenchymaCollenchyma– unevenly thick primary walls used for plant support unevenly thick primary walls used for plant support – no secondary walls ; no ligninno secondary walls ; no lignin

SclerenchymaSclerenchyma– support element strengthened by secondary cell walls with support element strengthened by secondary cell walls with

lignin (may be dead; xylem cells)lignin (may be dead; xylem cells)– fibers and sclereids for support fibers and sclereids for support

Plant GrowthPlant GrowthLife CyclesLife Cycles– annualsannuals: 1 year (wildflowers; food crops): 1 year (wildflowers; food crops)– biennialsbiennials: 2 years (beets; carrots): 2 years (beets; carrots)– perennialsperennials: many years (trees; shrubs): many years (trees; shrubs)MeristemsMeristems– apicalapical: tips of roots and buds; primary growth: tips of roots and buds; primary growth– laterallateral: cylinders of dividing cells along length : cylinders of dividing cells along length

of roots and stems; secondary growth (wood)of roots and stems; secondary growth (wood)– Primary growth is length vs. secondary Primary growth is length vs. secondary

growth is girthgrowth is girth

Primary growth in rootsPrimary growth in rootsRootsRoots

root caproot cap-protection of -protection of meristemmeristem

zone of cell divisionzone of cell division- - primary (apical) meristemprimary (apical) meristem

zone of elongationzone of elongation- cells - cells elongate; pushes root tipelongate; pushes root tip

zone of maturationzone of maturation- - differentiation of cells differentiation of cells (formation of 3 tissue (formation of 3 tissue systems)systems)

Primary Tissues of RootsPrimary Tissues of RootsSteleStele- the vascular bundle where both xylem and - the vascular bundle where both xylem and phloem developphloem develop

PithPith- central core of stele in monocot; parenchyma - central core of stele in monocot; parenchyma cellscells

CortexCortex- region of the root between the stele and - region of the root between the stele and epidermis (innermost layer: epidermis (innermost layer: endodermisendodermis))

Lateral rootsLateral roots- arise from - arise from pericyclepericycle (outermost layer of (outermost layer of stele); just inside endodermis, cells that may become stele); just inside endodermis, cells that may become meristematicmeristematic

Primary Tissues of StemsPrimary Tissues of Stems

Vascular bundles (xylem and phloem)Vascular bundles (xylem and phloem)

Surrounded by ground tissue (xylem faces pith Surrounded by ground tissue (xylem faces pith and phloem faces cortex)and phloem faces cortex)

Mostly parenchyma; some collenchyma and Mostly parenchyma; some collenchyma and sclerenchyma for supportsclerenchyma for support

Primary Tissues of LeavesPrimary Tissues of LeavesEpidermis/cuticle (protection; desiccation)Epidermis/cuticle (protection; desiccation)

StomataStomata (tiny pores for gas exchange and (tiny pores for gas exchange and transpiration)/transpiration)/guard cellsguard cells

MesophyllMesophyll– ground tissue between upper and lower epidermis ground tissue between upper and lower epidermis

(parenchyma with chloroplasts)(parenchyma with chloroplasts)– palisade (most photosynthesis) and spongy (gas palisade (most photosynthesis) and spongy (gas

circulation)circulation)

Secondary GrowthSecondary GrowthTwo lateral meristemsTwo lateral meristems– vascular cambium vascular cambium -produces secondary xylem -produces secondary xylem

(wood) and secondary phloem (diameter (wood) and secondary phloem (diameter increase; annual growth rings)increase; annual growth rings)

– cork cambium cork cambium -produces thick covering that -produces thick covering that replaces the epidermisreplaces the epidermis

produces cork cellsproduces cork cells

– barkbark-all tissues external to vascular cambium -all tissues external to vascular cambium (phloem plus periderm)(phloem plus periderm)