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Gas exchange
Photosynthesis
Transpiration
Xylem – water &
mineral transport
Water & mineral
absorption
Phloem –
sugar transport
Gas exchange –
cellular respiration
3 MAIN CELL
COMPARTMENTS
TISSUE COMPARTMENTS
•Symplast – travel via
cytosol continum
•Apoplast- travel via cell
walls
& extracellular spaces
ABSORPTION OF WATER
& MINERALS BY ROOTS
Mycorrhizae –
•Symbiotic
relationship
•Surface area for
absorption
TRANSPORT OF WATER
• Root pressure
• Guttation
• Transpirational pull
• Cohesion & adhesion
TRANSPIRATIONAL PULL
ASCENT OF WATER
•SOLAR POWERED
•HYDROGEN BONDING
•CHARACTERISTICS
OF WATER
CONTROL OF TRANSPIRATION
Photosynthesis – transpiration compromise
Stoma
open
Guard cells
Stoma
closed
Guard cells:
inner walls thicker, cellulose microfibrils
Guard cells:
regulated by uptake and loss of K+
Adaptations to reduce transpiration:
thick cuticle, recessed stomata
Stoma
TRANSLOCATION OF PHLOEM SAP
From source (sugar production) to sink (consumes
or stores sugar), pressure flow hypothesis
Chemiosmotic mechanism for
active transport of sucrose
PRESSURE FLOW
Loading of sugar reduces
water potential
Absorption of water generates
pressure and forces flow
Pressure gradient reinforced
by the unloading of sugar at the sink
Xylem recycles water
from sink to source
Tapping phloem-sap with the help
of an aphid
THE AVAILABILITY OF SOIL WATER &
MINERALS
• Roots hairs increase surface area
• Minerals actively transported in, water follows by osmosis
Soil Bacteria:
Nitrogen fixing & Ammonifying (decomposers)
Development of a
soybean root nodule
Pericycle layer gives rise
to secondary roots
Root nodules
on legumes
PARASITIC PLANT
CARNIVOROUS PLANTS
ANGIOSPERM LIFE CYCLE
sporophyte/gametophyte; diploid/haploid
FLOWER ANATOMY
Complete-all organs
Incomplete-lacking 1
or more organs
Bisexual – both
stamens & carpels
Unisexual-one or the
other
Monoeciouscarpellate &
staminate flowers
Dioecious-separate
plants
Angiosperm Gametophytes
Pollen grains
male
female
Reduce self - fertilization
Genetic Basis of SelfIncompatibility
Growth of
pollen tube and
double fertilization
*
*
Development of a Dicot Embryo
Above cotyledons
Below cotyledons
Embryonic root
Development
0f a pea fruit
Unique to monocots
GERMINATION
•
•
•
•
Imbibition
Release of Gibberellic acid
Aleurone  enzymes (α amylase)
Hydrolysis of endosperm
Seed Germination
- Radicle emerges 1st
a) Cotyledons pulled from soil
b) Hypocotyl emerges, cotyledons
remain in ground
c) Shoot grows up through coleoptile
ASEXUAL REPRODUCTION
(vegetative reproduction)
Fragmentation – separation of a parent plant into
parts that reform whole plants
Root system of a
single parent
gives rise to
many adventitious
shoots
Vegetative Propagation
- cuttings
PLANT RESPONSES TO
EXTERNAL SIGNALS
Light induced greening of
dark sprouted potatoes
Grass seedling
growing toward
light
Signal Transduction Pathway
(review)
TROPISMS
• Phototropism – response to light
– Stems (positive); Roots (negative)
• Gravitropism – response to gravity
– Stems (negative); Roots (positive)
• Thigmotropism – response to contact
– Curling around objects (vines)
PHOTOTROPISM
CONCLUSION
-CHEMICAL SIGNAL
PRESENT IN COLEOPTILE
TIP STIMULATES GROWTH
AS IT PASSED DOWN THE
COLEOPTILE
-HIGHER CONCENTRATION
OF CHEMICAL ON DARKER
SIDE CAUSED THE PLANT
GROWTH TO CURVE TOWARD
LIGHT
- NAMED THE CHEMICAL “AUXIN”
PLANT HORMONES
• Auxins – stem elongation in apical meristems
– Fruit maturation, prevents abscission
• Cytokinins – cell division in roots, embryos,
fruits
• Gibberellins – stem elongation in mature
regions, fruit development
• Abscisic acid – dormancy, stress, abscission
• Ethylene – fruit ripening
Apical Dominance:
•Terminal shoot inhibits lateral buds
•Auxin responsible
Gibberellins:
•Stimulate growth (elongation & division)
•Tall spindly plants
•Larger seedless grapes
Abscisic Acid (ABA)
•Seed dormancy
-Inhibits germination
•Stress
-Drought
-Winter
Leaf Abscisision
•Parenchyma cells
w/ very thin walls
•Change in balance
of auxin & ethylene
•Aging leaf produces
less & less auxin
Phytochrome regulation of lettuce
seeds
Pr ↔ Pfr acts as a switching mechanism
that controls various light-induced events
Functions as the
photoreceptor
Links light reception
to cellular responses
bluish
blue-greenish
Switched on by
Photoperiodic Control of Flowering
Short day plants flower
when night exceeds the
critical dark period
Long day plants flower
when night is shorter than
the critical dark period
Root Gravitropism
Smaller plant touched 2x/day
Rapid turgor movements
Response to flooding & oxygen deprivation