figure 29.1
DESCRIPTION
Figure 29.1. The Greening of Earth Looking at a lush landscape it is difficult to imagine the land without plants . For first 3 billion years of Earth’s history -terrestrial surface was lifeless. - PowerPoint PPT PresentationTRANSCRIPT
The Greening of Earth
• Looking at a lush landscape it is difficult to imagine the land without plants
For first 3 billion years of Earth’s history
-terrestrial surface was lifeless
• Land plants evolved f/ green algae
• The potato’s response to light• Is an example of cell-signal processing
Figure 39.3
CELLWALL
CYTOPLASM
1 Reception 2 Transduction 3 Response
Receptor
Relay molecules
Activationof cellularresponses
Hormone orenvironmentalstimulus
Plasma membrane
Figure 39.4
1 Reception 2 Transduction 3 Response
CYTOPLASM
Plasmamembrane
Phytochromeactivatedby light
Cellwall
Light
cGMP
Second messengerproduced
Specificproteinkinase 1activated
Transcriptionfactor 1 NUCLEUS
P
P
Transcription
Translation
De-etiolation(greening)responseproteins
Ca2+
Ca2+ channelopened
Specificproteinkinase 2activated
Transcriptionfactor 2
• Signal transduction in plants
1 The light signal isdetected by thephytochrome receptor,which then activatesat least two signaltransduction pathways.
2 One pathway uses cGMP as asecond messenger that activatesa specific protein kinase.The otherpathway involves an increase incytoplasmic Ca2+ that activatesanother specific protein kinase.
3 Both pathwayslead to expressionof genes for proteinsthat function in thede-etiolation(greening) response.
Adaptations for life on land
*
Alternation of generations*
Haploid multicellularorganism (gametophyte)
Mitosis Mitosis
Gametes
Zygote
Diploid multicellularorganism (sporophyte)
MEIOSIS FERTILIZATION
2n
2n
n
n
nn
nSpores
Mitosis
ALTERNATION OF GENERATIONS
Cuticle* (a waxy covering of the leaves) evolved in many plant species
Fossil evidence indicates that plants were on land at least 475 million years ago
• Land plants grouped• Based on the presence or absence of vascular tissue*
• Life cycles of bryophytes (e.g. moss) dominated by the gametophyte stage
Bryophyte Sporophytes• Dependant on gametophytes
Ferns and other seedless vascular plants* formed the first forests, evolved during Carboniferous period
Figure 29.15
• The growth of these early forests• May have helped produce the major global cooling that
characterized the end of the Carboniferous period• Decayed and eventually became coal
life cycle of a fern – alternation of generations
Fern sperm use flagellato swim from the antheridia to eggs in the archegonia.
4
Sporangia release spores.Most fern species produce a singletype of spore that gives rise to abisexual gametophyte.
1 The fern sporedevelops into a small,photosynthetic gametophyte.
2 Although this illustration shows an egg and sperm from the same gametophyte, a variety of mechanismspromote cross-fertilizationbetween gametophytes.
3
On the undersideof the sporophyte‘sreproductive leavesare spots called sori.Each sorus is acluster of sporangia.
6
A zygote develops into a newsporophyte, and the young plantgrows out from an archegoniumof its parent, the gametophyte.
5
MEIOSIS
Sporangium
Sporangium
Maturesporophyte
Newsporophyte Zygote
FERTILIZATION
ArchegoniumEgg
Haploid (n)Diploid (2n)
Spore Younggametophyte
Fiddlehead
Antheridium
Sperm
Gametophyte
Key
Sorus
Figure 29.12
Transport*
• Vascular plants have two types of vascular tissue*• Xylem* and phloem*
• Xylem*• Conducts water and minerals
• Phloem*• Distributes sugars, amino acids, and other organic products• Living cells
• Ascent of xylem sap - TranspirationXylemsapOutside air Y
= –100.0 MPa
Leaf Y (air spaces) = –7.0 MPa
Leaf Y (cell walls) = –1.0 MPa
Trunk xylem Y = – 0.8 MPa
Wat
er p
oten
tial g
radi
ent
Root xylem Y = – 0.6 MPa
Soil Y = – 0.3 MPa
MesophyllcellsStomaWatermolecule
Atmosphere
Transpiration
Xylemcells Adhesion Cell
wall
Cohesion,byhydrogenbonding
Watermolecule
Roothair
Soilparticle
Water
Cohesion and adhesionin the xylem
Water uptakefrom soil Figure 36.13
Vessel
(xylem)
H2OH2O
Sieve tube
phloem)
Source cell(leaf)
Sucrose
H2O
Sink cell(storageroot)
1
Sucrose
Loading of sugar (green dots) into the sieve tube at the source reduces water potential inside the sieve-tube members. This causes the tube to take up water by osmosis.
2
4 3
1
2 This uptake of water generates a positive pressure that forces the sap to flow along the tube.
The pressure is relieved by the unloading of sugar and the consequent loss of water from the tubeat the sink.
3
4 In the case of leaf-to-roottranslocation, xylem recycles water from sinkto source.
Tran
spira
tion
stre
am
Pres
sure
flow
Figure 36.18
Pressure Flow - Translocation• Sap moves through a sieve tube by bulk flow driven by
positive pressure
Evolution of Leaves• Increase the surface area of vascular plants, thereby
capturing more solar energy for photosynthesis
Keyto labels
DermalGroundVascular
Guardcells
Stomatal pore
Epidermalcell
50 µmSurface view of a spiderwort(Tradescantia) leaf (LM)
(b)Cuticle
Sclerenchymafibers
Stoma
Upperepidermis
Palisademesophyll
Spongymesophyll
Lowerepidermis
Cuticle
VeinGuard cells
XylemPhloem
Guard cells
Bundle-sheathcell
Cutaway drawing of leaf tissues(a)
Vein Air spaces Guard cells
100 µmTransverse section of a lilac(Syringa) leaf (LM)
(c)Figure 35.17a–c
Leaf anatomy
• Absorption spectra of 3 types of pigments
Three different experiments helped reveal which wavelengths of light are photosynthetically important. The results are shown below.
EXPERIMENT
RESULTS
Abs
orpt
ion
of li
ght b
ych
loro
plas
t pig
men
ts
Chlorophyll a
(a) Absorption spectra. The three curves show the wavelengths of light best absorbed by three types of chloroplast pigments.
Wavelength of light (nm)
Chlorophyll b
Carotenoids
Figure 10.9
E Transformations Thermodynamics• E flows into ecosystem as sunlight, leaves as heat
Light energy
ECOSYSTEM
CO2 + H2O
Photosynthesisin chloroplasts
Cellular respirationin mitochondria
Organicmolecules + O2
ATP
powers most cellular work
HeatenergyFigure 9.2
• Review
Light reactions:• Are carried out by molecules in the thylakoid membranes• Convert light energy to the chemical energy of ATP and NADPH• Split H2O and release O2 to the atmosphere
Calvin cycle reactions:• Take place in the stroma• Use ATP and NADPH to convert CO2 to the sugar G3P• Return ADP, inorganic phosphate, and NADP+ to the light reactions
O2
CO2H2O
Light
Light reaction Calvin cycle
NADP+
ADP
ATP
NADPH
+ P 1
RuBP 3-Phosphoglycerate
Amino acidsFatty acids
Starch(storage)
Sucrose (export)
G3P
Photosystem IIElectron transport chain
Photosystem I
Chloroplast
Figure 10.21
Seeds* changed the course of plant evolution• Enabling their bearers to become the dominant* producers
in most terrestrial ecosystems
Figure 30.1
Pollen*, (dispersed by air or animals *)• Eliminated the water requirement for fertilization
The Evolutionary Advantage of Seeds*** • A seed ***
• Develops from the whole ovule• Embryo, + food supply, packaged in a protective coat*
Figure 30.3c
Gymnosperm seed. Fertilization initiatesthe transformation of the ovule into a seed,which consists of a sporophyte embryo, a food supply, and a protective seed coat derived from the integument.
(c)
Seed coat(derived fromIntegument)
Food supply(femalegametophytetissue) (n)
Embryo (2n)(new sporophyte)
Angiosperm Evolution• Originated at least 140 mya during the late Mesozoic
Fungi
Symbionts• Symbiotic relationships w/
• Plants, algae, and animals
Lichens• Symbiotic association of millions of photosynthetic
microorganisms held in a mass of fungal hyphae
(a) A fruticose (shrub-like) lichen
(b) A foliose (leaf-like) lichen (c) Crustose (crust-like) lichensFigure 31.23a–c
• Fungi plus algae or cyanobacteria
Ascocarp of fungus
Fungalhyphae
Algallayer
Soredia
Algal cell
Fungal hyphae
10
m
Figure 31.24
Mycorrhizae• Enormously important in natural ecosystems and
agriculture
RESULTS
Researchers grew soybean plants in soil treated with fungicide (poison that kills fungi) to prevent the formation of mycorrhizae in the experimental group. A control group was exposed to fungi that formed mycorrhizae in the soybean plants’ roots.
EXPERIMENT
The soybean plant on the left is typical of the experimental group. Its stunted growth is probably due to a phosphorus deficiency. The taller, healthier plant on the right is typical of the control group and has mycorrhizae.
CONCLUSION These results indicate that the presence of mycorrhizae benefits a soybean plant and support the hypothesis that mycorrhizae enhance the plant’s ability to take up phosphate and other needed minerals.Figure 31.21
RESULTS