Ch. 35 Warm-UpCh. 35 Warm-Up

1.What are 3 ways that plant cells differ from animal cells?

2.Most H2O and minerals taken up from the soil by a plant are absorbed by _______.3.The main photosynthetic organs of a plant are the __________.

Chapter 35Chapter 35Plant Structure, Growth, and Development

What you must knowWhat you must knowThe function of xylem and

phloem tissue.The anatomy of a leafThe anatomy of a root

Introduction to PlantsIntroduction to PlantsKingdom: Plantae

Cell wall Autotroph (photosynthesis) Multicellular Angiosperms (flowering plants)

~90% plantsProduce seeds within a fruitKey adaptations: flowers & fruits

Plant OrganizationPlant Organization

•Above ground•Stems, leaves

•Underground (usually)•Roots

Shootsystem

Rootsystem

I. Plant OrgansI. Plant Organs

A. RootsA. Roots Anchors plant, absorbs H2O &

minerals, stores sugars/starches Root hairs – tiny extensions of

epidermal cells, increase surface area for H2O and mineral absorption

Mycorrhizae: fungus + plant root symbiotic relationship

Root hairs

Fibrous Root(scallion)

Taproot(carrot)

Fibrous RootsMat of thin roots spread

just below surfaceShallow Increased surface area

TaprootsOne thick, vertical rootMany lateral (branch)

rootsFirmly anchorsStores food

Modified RootsModified Roots

Mangrove Forest in FloridaMangrove Forest in Florida

B. StemsB. StemsFunction: display leaves

Terminal bud: growth concentrated at top end of stem Secretes hormone to

prevent growth of axillary buds; growth directed upward, toward light

Axillary buds – located in V between leaf and stem; forms branches (lateral shoots) Pinching/pruning –

removing terminal bud

Modified stemsModified stemsRunner or stolin

◦ Aspen, strawberries, grass◦ Grow on surface◦ For asexual reproduction

Rhizome◦ Iris, ginger, potato, onion◦ Grow underground◦ Store food & DNA for new plant◦ Tuber: end of rhizome

Bulb – underground shoot◦ Onion ◦ storage leaves

C. LeavesC. LeavesFunction: Photosynthetic organ

petiole

blade

Modified Modified leavesleaves

II. Plant II. Plant TissuesTissues

A. Dermal TissueA. Dermal TissueSingle layer, closely packed cells that

cover entire plantProtect against water loss & invasion

by pathogens (viruses, bacteria)Cuticle: waxy layer

B. Vascular TissueB. Vascular TissueContinuous throughout plantTransports materials between roots &

shoots◦ XylemXylem & PhloemPhloem

C. Ground TissueC. Ground TissueAnything that isn’t dermal or vascularFunction: storage, photosynthesis,

supportPith: inside vascular tissueCortex: outside vascular tissue

III. Cell TypesIII. Cell TypesA.A. XylemXylem

Conducts H2O and minerals up from root

Dead, tubular, elongated cellsB.B. PhloemPhloem

Conducts sugar & organic compounds from leaves to other parts of plant

Living cells aid movement of sugar 2 Cell Types: sieve tubes,

companion cells

Xylem Phloem

Plant GrowthPlant GrowthTypes of Flowering Plants:Annuals – 1 year life cycleBiennials – 2 yearsPerennials – continuous life cycle for many

years

Meristem: perpetually embryonic tissues◦Cells divide for plant growthApical meristem: growth at tips of roots

& buds of shoots; cause primary growth (increase length)

Lateral meristem: growth thickens shoots and roots; secondary growth

Primary and Secondary Primary and Secondary GrowthGrowth

Root AnatomyRoot Anatomy

Root cap: protects meristem as it pushes through soil

Zone of Cell Division: apical meristem; new cells produced (mitosis)

Zone of Elongation: cells elongate; push root tip ahead

Zone of Maturation: primary growth becomes functionally mature

Root Hairs

Leaf AnatomyLeaf Anatomy◦ Epidermis of underside interrupted by stomata

(pores), flanked by guard cells (open/close stomata)

◦ Mesophyll: ground tissue between upper/lower epidermis

◦ Parenchyma: sites of photosynthesis

Secondary Growth = increase Secondary Growth = increase diameterdiameterInvolves lateral meristems

◦Vascular cambium: produces secondary xylem (wood)

◦Cork cambium: produces tough covering that replaces epidermis

Bark = all tissues outside vascular cambium

Primary and secondary growth in a two-year-old stem

Epidermis

Cortex

Growth

Xylemray

Vascularcambium

Primaryphloem

Pith

Primaryxylem Phloem ray

EpidermisCortex

Vascular cambiumPrimary phloem

PithPrimary xylem

Vascular cambium

Primary phloem

Primaryxylem

Secondary phloem

Secondary xylem

First cork cambium Cork

Growth

0.5 mm

Vascular cambiumSecondary phloem

Secondaryxylem

Transverse sectionof a three-year-old Tilia (linden)stem (LM)

Late woodEarly wood

0.5 mm

Cork cambium

Cork

Periderm

Xylem rayBark

Vascular cambium

Primary phloem

Secondary phloem

Secondary xylem

Periderm(mainly corkcambiaand cork)

Primary xylem

Pith

Vascular cambium

Secondary phloem

Secondaryxylem (twoyears ofproduction)

Cork

Bark

Layers ofperiderm

Most recentcork cambium

Primary and Primary and Secondary Secondary Growth of a Growth of a

StemStem

Chapter 38Chapter 38Angiosperm Reproduction

Angiosperms have 3 unique Angiosperms have 3 unique Features:eatures:

1.1. FFlowers2.2. FFruits3. Double

FFertilization (by 2 sperm)

REPRODUCTIVE VARIATIONS

Pollination: transfer pollen from anther to stigma

Some plants are self-pollinatedCross-pollinated plants:

◦Self-incompatibility: plant rejects own pollen or closely related plant

◦Maximize genetic variation

Stigma Stigma

Pin flower

Antherwith

pollen

Thrum flower

““PinPin”” and and ““thrumthrum”” flower types reduce self-fertilization flower types reduce self-fertilization

The development of a plant embryoThe development of a plant embryo

FruitFruitEgg cell Egg cell plant embryoplant embryoOvulesOvules inside ovary seedsseedsRipe ovaryovary fruitfruitFruit protects enclosed seed(s)Aids in dispersal by water, wind,

or animals

SeedsSeedsMature seed dormancy (resting)

◦ Low metabolic rate◦ Growth & development suspended◦ Resumes growth when

environmental conditions suitable for germination

GerminationGermination Seed take up water (imbibition)

trigger metabolic changes to begin growth

◦ Root develops shoot emerges leaves expand & turn green (photosynthesis)

Very hazardous for plants due to vulnerability Predators, parasites, wind

SexualAsexual

(Vegetative Reproduction)

Flower Seeds

Runners, bulbs, grafts, cuttings

vegetative (grass), fragmentation, test-tube

cloning

Genetic diversity Clones

More complex & hazardous for seedlings

Simpler (no pollinator needed)

Advantage in unstable environments

Suited for stable environments

Plant ReproductionPlant Reproduction

Asexual Asexual reproduction reproduction in aspen treesin aspen trees

Test-tube cloning Test-tube cloning of carrotsof carrots

Humans Modify CropsHumans Modify CropsArtificial selection of plants for breedingPlant Biotechnology:

◦Genetically modified organisms “Golden Rice”: engineered to produce

beta-carotene (Vit. A) Bt corn: transgenic – expresses Bt

(bacteria) gene produces protein toxic to insects

◦Biofuels – reduce CO2 emissions Biodiesel: vegetable oils Bioethanol: convert cellulose into

ethanol