PlantsPlants
Chapter 23Chapter 23
Setting the Stage for Setting the Stage for PlantsPlants
Earth’s atmosphere was originally oxygen Earth’s atmosphere was originally oxygen freefree
Ultraviolet radiation bombarded the Ultraviolet radiation bombarded the surfacesurface
Photosynthetic cells produced oxygen and Photosynthetic cells produced oxygen and allowed formation of a protective ozone allowed formation of a protective ozone layerlayer
Invading the LandInvading the Land
Cyanobacteria were probably the first to Cyanobacteria were probably the first to
spread into and up freshwater streamsspread into and up freshwater streams
Later, green algae and fungi made the Later, green algae and fungi made the
journey togetherjourney together
Every plant is descended from species of Every plant is descended from species of
green algae green algae
The Plant KingdomThe Plant Kingdom
Nearly all are multicelled Nearly all are multicelled
Vast majority are photoautotrophs Vast majority are photoautotrophs
Energy from sunEnergy from sun
Carbon dioxide from airCarbon dioxide from air
Minerals dissolved in waterMinerals dissolved in water
Evolutionary Tree for Evolutionary Tree for PlantsPlants
greenalgae
zygophytes, related groups
charophytes bryophytes lycophytes horsetails cycads conifersflowering
plants
seed plants
euphyllophytes
vascular plants
embryophytes (land plants)
(closely related groups)
ferns ginkgos gnetophytes
Nested monophyletic groups
Figure 23.3Page 387
Nonvascular PlantsNonvascular Plants
BryophytesBryophytes
Fewer than 19,000 speciesFewer than 19,000 species
Three groupsThree groups
LiverwortsLiverworts
Hornworts Hornworts
Mosses Mosses
Vascular PlantsVascular Plants
Majority of plantsMajority of plants
Have internal tissues that carry water and Have internal tissues that carry water and
solutessolutes
Two groupsTwo groups
Seedless vascular plantsSeedless vascular plants
Seed-bearing vascular plantsSeed-bearing vascular plants
Seedless Vascular PlantsSeedless Vascular Plants
Arose during the DevonianArose during the Devonian Produce spores but no seedsProduce spores but no seeds Four main groupsFour main groups
Whisk fernsWhisk ferns
LycophytesLycophytes
HorsetailsHorsetails
FernsFerns
Seed-Bearing Vascular Seed-Bearing Vascular PlantsPlants
Gymnosperms arose firstGymnosperms arose first CycadsCycads GinkgosGinkgos GnetophytesGnetophytes ConifersConifers
Angiosperms arose laterAngiosperms arose later MonocotsMonocots DicotsDicots
Evolutionary TrendEvolutionary Trend
zygote
SPOROPHYTE (2n)
GAMETOPHYTE (n)
GREEN ALGA BRYOPHYTE FERN GYMNOSPERM ANGIOSPERM
Figure 23.2Page 386
Adaptations to LandAdaptations to Land
Root systemsRoot systems
Shoot systemsShoot systems
Vascular tissues Vascular tissues
Waxy cuticle Waxy cuticle
Traits of Traits of Seed-Bearing PlantsSeed-Bearing Plants
Pollen grainsPollen grains Arise from megasporesArise from megaspores Develop into male gametophytesDevelop into male gametophytes Can be transported without waterCan be transported without water
SeedsSeeds Embryo sporophyte inside nutritive tissues Embryo sporophyte inside nutritive tissues
and a protective coatand a protective coat Can withstand hostile conditionsCan withstand hostile conditions
BryophytesBryophytes
Small, nonvascular, nonwooody Small, nonvascular, nonwooody Gametophyte dominates life cycle; Gametophyte dominates life cycle;
has leaflike, stemlike, and rootlike has leaflike, stemlike, and rootlike partsparts
Usually live in wet habitatsUsually live in wet habitats Flagellated sperm require water to Flagellated sperm require water to
reach eggsreach eggs
Types of BryophytesTypes of Bryophytes
Mosses (most common)Mosses (most common)
Liverworts (simplest)Liverworts (simplest)
Hornworts Hornworts
Moss Life CycleMoss Life Cycle
Zygote grows, develops into a sporophyte while still attached to gametophyte.
Fertilization
zygote
sperm-producing structure
egg-producing structure
Diploid Stage
Haploid Stage
mature sporophyte
Meiosis
Spores germinate.
male gametophyte
female gametophyteFigure 23.5
Page 388
Peat MossesPeat Mosses
350 species350 species
SphagnumSphagnum is an example is an example
Grow in acidic bogs; important ecosystems of Grow in acidic bogs; important ecosystems of
cold and temperate regionscold and temperate regions
Peat can be harvested and burned as fuelPeat can be harvested and burned as fuel
Marchantia:Marchantia: A Liverwort A Liverwort
Reproduces Reproduces asexually by asexually by gemmae gemmae
Gametophytes are Gametophytes are
male or femalemale or female
Female gametophyte
Do not post on Internet
Figure 23.7 Page 389
Seedless Vascular Seedless Vascular PlantsPlants
Like bryophytesLike bryophytes
Live in wet, humid placesLive in wet, humid places
Require water for fertilizationRequire water for fertilization
Unlike bryophytesUnlike bryophytes
Sporophyte is free-living and Sporophyte is free-living and
has vascular tissueshas vascular tissues
Seedless Vascular PlantsSeedless Vascular Plants
Lycophytes (Lycophyta)Lycophytes (Lycophyta)
Whisk ferns (Psilophyta)Whisk ferns (Psilophyta)
Horsetails (Sphenophyta)Horsetails (Sphenophyta)
Ferns (Pterophyta)Ferns (Pterophyta)
Ferns (Pterophyta)Ferns (Pterophyta)
12,000 species, mostly tropical12,000 species, mostly tropical Most common sporophyte structureMost common sporophyte structure
Perennial underground stem (rhizome)Perennial underground stem (rhizome) Roots and fronds arise from rhizomeRoots and fronds arise from rhizome Young fronds are coiled “fiddleheads”Young fronds are coiled “fiddleheads” Mature fronds divided into leafletsMature fronds divided into leaflets Spores form on lower surface of some Spores form on lower surface of some
frondsfronds
Fern Life CycleFern Life Cycle
Spores are released
Sporophyte still attached to gametophyte
zygote
fertilizationDiploid StageHaploid Stage
egg
sperm
mature gametophyte
Spores develop
meiosis
Spore germinates
rhizomesorus
Figure 23.9Page 391
Rise of Seed-Bearing Rise of Seed-Bearing PlantsPlants Seeds appeared about 360 million Seeds appeared about 360 million
years ago years ago
Seed ferns and gymnosperms were Seed ferns and gymnosperms were
dominant at firstdominant at first
Angiosperms arose laterAngiosperms arose later
CarboniferousCarboniferous
Giant lycophytes and horsetails Giant lycophytes and horsetails
Sea level rose and fell repeatedly Sea level rose and fell repeatedly
Remains of swamp forests were Remains of swamp forests were repeatedly submerged and repeatedly submerged and compressedcompressed
Formation of coalFormation of coal
Seed-Bearing Plants Seed-Bearing Plants
Microspores that give rise to pollen Microspores that give rise to pollen
grainsgrains
Megaspores inside ovulesMegaspores inside ovules
More water-conserving than More water-conserving than
seedless vascular plantsseedless vascular plants
Pollen Pollen
Pollen grains are sperm-bearing male Pollen grains are sperm-bearing male gametophytes that develop from gametophytes that develop from microsporesmicrospores
Allows transfer of sperm to egg without Allows transfer of sperm to egg without waterwater
Can drift on air currents or be carried by Can drift on air currents or be carried by pollinatorspollinators
OvulesOvules
Female reproductive structures that Female reproductive structures that become seedsbecome seeds
Consist of:Consist of: Female gametophyte with egg cellFemale gametophyte with egg cell
Nutrient-rich tissueNutrient-rich tissue
Jacket of cell layers that will form seed coatJacket of cell layers that will form seed coat
GymnospermsGymnosperms
Plants with “naked seeds”Plants with “naked seeds”
Seeds don’t form inside an ovarySeeds don’t form inside an ovary
Four groupsFour groups
ConifersConifers GinkgosGinkgos
CycadsCycads GnetophytesGnetophytes
Conifer Characteristics Conifer Characteristics
Widest known, largest number of living Widest known, largest number of living speciesspecies
Woody trees or shrubs Woody trees or shrubs
Most are evergreenMost are evergreen
Bear seeds on exposed cone scalesBear seeds on exposed cone scales
Most produce woody conesMost produce woody cones
CycadsCycads
Most diverse during Most diverse during age of dinosaursage of dinosaurs
Only 100 living speciesOnly 100 living species Palmlike appearancePalmlike appearance Pollen-bearing and Pollen-bearing and
seed-bearing cones on seed-bearing cones on different plantsdifferent plants Do not
post on Internet
Figure 23.14ePage 394
Strobilus of a “female” cycad
GinkgosGinkgos
Diverse during age Diverse during age of dinosaursof dinosaurs
One surviving One surviving species, species, Ginkgo Ginkgo biloba biloba
Deciduous trees are Deciduous trees are male or female male or female
Do not post
photos on
Internet
Fig. 23.15 Page 395
3 Genera of Gnetophytes3 Genera of Gnetophytes
GnetumGnetum
WelwitschiaWelwitschia
EphedraEphedra Sporophyte of Ephedra
Do not post on Internet
Figure 23.16aPage 395
Pine ConesPine Cones
Woody scales of a “pine cone” are the Woody scales of a “pine cone” are the
parts where megaspores formed and parts where megaspores formed and
developed into female gametophytesdeveloped into female gametophytes
Male cones, where microspores and Male cones, where microspores and
pollen are produced, are not woodypollen are produced, are not woody
section through one ovule
ovule
surface view of one cone scale (houses two ovules)
section through a pollen-producing sac
surface view of one cone scale (houses a pollen-producing sac)
meiosisfertilization
seed coat
embryo
zygote
mature sporophyte
seeding
pollen tube
sperm-producing cell
eggs
female gametophyte
pollination
microspores form
megaspores form
seedDiploid
Haploid
Pine Life CyclePine Life Cycle
Figure 23.17Page 396
Conifer DistributionConifer Distribution
Reproduce more slowly than Reproduce more slowly than angiosperms; at competitive angiosperms; at competitive disadvantage in many habitatsdisadvantage in many habitats
Still dominate in far north, at higher Still dominate in far north, at higher elevations, and in certain parts of elevations, and in certain parts of southern hemispheresouthern hemisphere
AngiospermsAngiosperms Flowering plantsFlowering plants
Dominant land plants (260,000 species)Dominant land plants (260,000 species)
Ovules and (after fertilization) seeds are Ovules and (after fertilization) seeds are enclosed in an ovaryenclosed in an ovary
Three main groups: magnoliids, Three main groups: magnoliids, monocots, and eudicotsmonocots, and eudicots
Angiosperm Evolutionary Angiosperm Evolutionary TreeTree
basal groups
Amborellawater lilies
star anise magnoliids monocots eudicots
Figure 23.19aPage 398
Double Fertilization Double Fertilization
Distinctive feature of angiospermsDistinctive feature of angiosperms
Male gametocyte delivers two sperm to Male gametocyte delivers two sperm to an ovulean ovule
One fertilizes egg; other fertilizes a cell One fertilizes egg; other fertilizes a cell that gives rise to endosperm that gives rise to endosperm
FloweriFlowering Plant ng Plant Life Life Cycle Cycle
Double fertilization Meiosis Meiosis
microspores
female gametophyte
pollination
mitosis without cytoplasmic division
two sperm enter ovule
Diploid
Haploid
Figure 23.20Page 399
sporophyte
People and PlantsPeople and Plants
Plant domestication began about Plant domestication began about 11,000 years ago11,000 years ago
About 3,000 species have been About 3,000 species have been used as foodused as food
Now about 200 plants are major Now about 200 plants are major cropscrops
Nonfood Uses of Plants Nonfood Uses of Plants
Lumber, paper, and fuel Lumber, paper, and fuel
Furniture Furniture
Rope Rope
Thatched roofing Thatched roofing
Natural insecticidesNatural insecticides
Drugs Drugs
Plants of AbusePlants of Abuse
Tobacco plants are Tobacco plants are NicotianaNicotiana sp.sp. Cannabis sativaCannabis sativa is source of marijuana is source of marijuana Coca leaves are used to produce cocaineCoca leaves are used to produce cocaine Toxic plant alkaloids, such as henbane Toxic plant alkaloids, such as henbane
and belladona, have been used as and belladona, have been used as poisons and as medicinepoisons and as medicine