Chapter 7BOT3015L

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

•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

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

Note that this is a depiction with some gaps and misrepresentations for summary purposes

Triose phosphates

Transport Summary

A=absorption / assimilationL=loadingU=unloadingI=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 observationsWhat 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 AdaptationsResponses 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 AdaptationsResponses to Water Availability

Note large volume-to-

surface 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

Photo by Jean Burns at Hosford bogPlants in motionVenus fly trap

Venus fly trap (Diaonaea)

Pitcher plant(Sarracenia)

Example of highly specialized leaves

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

Lilac (Syringa)Cross-section, midvein of leaf

Three tissue systems in leaves too

Cross-section, blade of leaf

Lilac (Syringa)

Isolated epidermis stained with neutral red (vital stain that stains compartments of living cells)

Stomataadaptations to terrestrial environments

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 Stomata typical of monocots

Potato (Solanum) Maize (Zea)

Scanning electron microscope images

Scanning electron microscope image

Stomata and trichome of tobacco (Nicotiana)

Morphological AdaptationsResponses 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

Oleander (Nerium)Trichomes and sunken stomata

Morphological AdaptationsResponses to Water Availability

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 ExchangeOpen & Closed Stomata

Stomata animationModified from Outlaw lecture

Photos from Outlaw’s lab and also featured on the cover of the scientific

journal Archives of Biochemistry and Biophysics

Fava bean (Vicia)

Gas Exchange (g)Ion Transport—stomatal opening

Inside cell

Membrane

Proton extrusion makes membrane potential more negative and acidifies apoplast.

Water influx

Potassium uptake.

Thermodynamics: MP

Mechanism: MP & wall acidification activate the Kin channel

Modified from Outlaw WH, Jr. Integration of cellular and physiological functions of guard cells. CRC Crit Rev Plant Sci 22: 503-529

E. Water influx increases pressure, but water is incompressible, so guard-cell volume increases. The increase results from stretching of the dorsal wall.

A. Guard-cell symplast accumulate solutes from guard-cell apoplast.

C. Radial micellation of cellulose microfibrils prevents increase of cell diameter.

B. Water flows into guard cells osmotically.M

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BR

AN

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D. Inner wall is strong and cannot be stretched.

Gas Exhange (e)Stomatal swelling

Modified from Outlaw lecture

Gas Exchange (j)Ion Transport—stomatal closing

Membrane

Inside cell

B. Potassium efflux.

Thermodynamics: MP

Mechanism: MP activates the Kout

channel

A. Anion efflux shifts the membrane potential to a less negative position.

Modified from Outlaw WH, Jr. Integration of cellular and physiological functions of guard cells. CRC Crit Rev Plant Sci

22: 503-529

ABA activates the Kout channel via cytosolic alkalinization.

Gas Exchangeion transport—ABA action

Membrane

Inside cell

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).

Modified from Outlaw WH, Jr. Integration of cellular and physiological functions of guard cells. CRC Crit Rev Plant Sci 22: 503-529

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

• Drawings

• Methods

• Data

• Review questions

QUIZ NEXT WEEK