Chapter 7
BOT3015L
Regulation of Gas Exchange
of Terrestrial Plants
Presentation created by Danielle Sherdan
All photos from Raven et al. Biology of Plants except when otherwise noted
Today
• Review photosynthesis and bulk transport in plants
• Observing leaf morphology
• Examples of highly modified leaves
• Leaf anatomy
• Stomata, adaptations to terrestrial environments
• Stomata aperture changes
• Further understanding of stomata by experimentation
The main ideas from last week’s
look at the anatomy of the
angiosperm plant body
Photosynthesis
primarily occurs
in chloroplasts of
leaves
Lilac (Syringa)
Review of photosynthesis
Triose phosphates
Note that this is a depiction with some gaps and misrepresentations for
summary purposes
Transport Summary
A=absorption / assimilation
L=loading
U=unloading
I=interchange
Today
• Review photosynthesis and bulk transport in plants
• Observing leaf morphology
• Examples of highly modified leaves
• Leaf anatomy
• Stomata, adaptations to terrestrial environments
• Stomata aperture changes
• Further understanding of stomata by experimentation
Leaf observations
What characteristics of leaves
make them well-adapted for their
function?
Today
• Review photosynthesis and bulk transport in plants
• Observing leaf morphology
• Examples of highly modified leaves
• Leaf anatomy
• Stomata, adaptations to terrestrial environments
• Stomata aperture changes
• Further understanding of stomata by experimentation
Morphological Adaptations
Responses to Water Availability
Waterlily (Nymphaea)
Note the misnomer, waterlilies are not in the
Liliaceae family
Note the abundant of air spaces.
This plant grows in water.
Modified from Outlaw lecture
Morphological Adaptations
Responses to Water Availability
Note large
volume-tosurface area
ratio ideal for dry
environment
Spines
(modified
leaves) protect
the water-filled
plant body
from predation
Ferocactus
Example of turgor control of quick
responses in highly specialized leaves
Venus fly trap (Diaonaea)
Photo by Jean Burns at Hosford bog
Plants in motion
Venus fly trap
Example of highly specialized leaves
Pitcher plant
(Sarracenia)
Photos from www.serracenia.com
Today
• Review photosynthesis and bulk transport in plants
• Observing leaf morphology
• Examples of highly modified leaves
• Leaf anatomy
• Stomata, adaptations to terrestrial environments
• Stomata aperture changes
• Further understanding of stomata by experimentation
Three tissue systems in leaves too
Cross-section, midvein of leaf
Lilac (Syringa)
Cross-section, blade of leaf
Stomata
adaptations to terrestrial environments
Lilac (Syringa)
Isolated epidermis stained with neutral red
(vital stain that stains compartments of living cells)
Today
• Review photosynthesis and bulk transport in plants
• Observing leaf morphology
• Examples of highly modified leaves
• Leaf anatomy
• Stomata, adaptations to terrestrial environments
• Stomata aperture changes
• Further understanding of stomata by experimentation
Stomata typical of dicots
Potato (Solanum)
Stomata typical of monocots
Maize (Zea)
Scanning electron microscope images
Stomata and trichome of tobacco (Nicotiana)
Scanning electron microscope image
Morphological Adaptations
Responses to Water Availability
Banksia
Note sunken stomata.
. . . Sunken stomata
increase the distance from
the moist leaf interior to
the bulk atmosphere. Flux
Equation!
Modified from Outlaw lecture
Morphological Adaptations
Responses to Water Availability
Oleander (Nerium)
Trichomes and sunken stomata
Today
• Review photosynthesis and bulk transport in plants
• Observing leaf morphology
• Examples of highly modified leaves
• Leaf anatomy
• Stomata, adaptations to terrestrial environments
• Stomata aperture changes
• Further understanding of stomata by experimentation
Gas Exchange
Open & Closed Stomata
Photos from Outlaw’s lab and
also featured on the cover of the scientific
journal Archives of Biochemistry and
Biophysics
Fava bean (Vicia)
Stomata animation
Modified from Outlaw lecture
Gas Exchange (g)
Ion Transport—stomatal opening
Proton extrusion makes
membrane potential more
negative and acidifies
apoplast.
Potassium uptake.
Water influx
Thermodynamics: MP
Mechanism: MP &
wall acidification
activate the Kin channel
Inside
cell
Membrane
Modified from Outlaw WH, Jr. Integration of cellular and physiological functions of guard
cells. CRC Crit Rev Plant Sci 22: 503-529
Gas Exhange (e)
CELL WALL
MEMBRANE
Stomatal swelling
A. Guard-cell symplast
accumulate solutes from
guard-cell apoplast.
B. Water flows into guard
cells osmotically.
C. Radial micellation of
cellulose microfibrils
prevents increase of cell
diameter.
D. Inner wall is strong
and cannot be stretched.
Modified from Outlaw lecture
E. Water influx increases
pressure, but water is
incompressible, so guard-cell
volume increases. The increase
results from stretching of the
dorsal wall.
Gas Exchange (j)
Ion Transport—stomatal closing
A. Anion efflux shifts
the membrane potential
to a less negative
position.
B. Potassium efflux.
Thermodynamics: MP
Inside
cell
Mechanism: MP
activates the Kout
channel
Modified from Outlaw WH, Jr. Integration of cellular and
physiological functions of guard cells. CRC Crit Rev Plant Sci
22: 503-529
Membrane
Gas Exchange
ion transport—ABA action
ABA may be made in roots and
transported to shoots, or made
by leaves, or even by guard
cells.
ABA activates the anion
channel, directly or by several
means indirectly (e.g., via Ca2+
signaling).
Inside
cell
ABA activates the Kout
channel via cytosolic
alkalinization.
Modified from Outlaw WH, Jr. Integration of
cellular and physiological functions of guard
cells. CRC Crit Rev Plant Sci 22: 503-529
Membrane
Today
• Review photosynthesis and bulk transport in plants
• Observing leaf morphology
• Examples of highly modified leaves
• Leaf anatomy
• Stomata, adaptations to terrestrial environments
• Stomata aperture changes
• Further understanding of stomata by experimentation
What internal and external factors
likely affect stomatal aperture?
What are the effects of CO2 on stomatal aperture?
Why do we want to know? How is this important?
About 1700 gallons of water are required to grow food for one
adult in the US per day!
(From 1993 National Geographic)
Experimental Design
The question:
What are the effects of CO2 on stomatal aperture?
How can we manipulate CO2 concentration?
One way:
CO2 + NaOH => NaHCO3 (sodium bicarbonate)
In notebook and checked
before you leave
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Drawings
Methods
Data
Review questions
QUIZ NEXT WEEK