Today:

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• Today
• Water Stress
• and
• Genetically Modifying Plants

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Fig 37.11
Water moves from the ground through roots into
the shoot and out stomata in the leaves.
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What happened to this root?
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Flooding, constant submersion Why would the
plant respond like this?
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Stomata control entry of CO2 and exit of H2O from
plant leaves
Fig 30.10
Stomata
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What about when water is scarce?
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Oleander
Structural adaptations of a plant that grows in
an arid environment
Fig 37.16
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Oleander

• Structural adaptations of a plant that grows in
  an arid environment
• Thick cuticle
• Thick epidermis
• Recessed stomata

Fig 37.16
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Stomata density can change depending on the
environment. Typically 200-300/mm2
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Individual plants can change stomata number to
adjust for changes in the environment.
New leaves develop with fewer stomata
Only mature leaves exposed to high CO2
JA Lake et al (10 May 2001) Nature 411, 154
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Measurements of herbarium samples and present day
samples have shown a 40 decrease in stomata over
the last 200 years.
F. I. Woodward (18 June 1987) Nature 327, 617 -
618
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Changes in precipitation 1900-2000
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Irrigating crops eventually leads to increased
soil salinity
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Freshwater is not pure water. It contains many
salts, such as sodium 6mg/L chloride 7mg/L
calcium 15mg/L sulfate 11mg/L silica 7mg/L
magnesium 4mg/L and potassium 3mg/L
http//science.jrank.org/pages/2857/Freshwater.htm
l
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Human resource production and use
http//www.earth-policy.org/Indicators/Grain/2006.
htm
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Worldwide Grain Production per Person
http//www.earth-policy.org/Indicators/Grain/2006.
htm
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Land use in USA, 1997
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from Teosinte
Maize
By artificial selection that began 10,000 years
ago.
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Genetic Engineering Direct manipulation of DNA
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We can now insert new genes or modify existing
genes of plants
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Agrobacterium infect plants, inserting some of
their DNA into the plants genome.
Fig 19.17
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Agrobacterium infect plants, inserting some of
their DNA into the plants genome.
Fig 19.17
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Fig 19.17
After inserting a gene into the Agrobacteria,
they will insert that gene into the plant's DNA.
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Global area planted with GM crops
Texas 70 ha
Millions of Hectares
http//www.gmo-compass.org/eng/agri_biotechnology/
gmo_planting/257.global_gm_planting_2006.html
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The agricultural release of genetically modified
organisms is the largest scale experiment that
has ever been performed.
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Tbl 19.5
Why Change a Plants DNA?

• Can change plant so that it has new or different
  characteristics
• Insect resistance (Bt toxin)
• Herbicide resistance (Round-up)
• Drought or other stress resistance

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Common GM Crops in the U.S.
of Total US Acres
http//blog.wired.com/wiredscience/2007/09/monsant
o-is-hap.html
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Are Genetically Modifying Plants Safe?
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Human impacts Dead zone in Gulf of Mexico from
Mississippi River
http//blog.nola.com/times-picayune/2007/06/despit
e_promises_to_fix_it_the.html
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Pollen is easily transferred from plant to plant,
and to related species.
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Genetic information moves.
GM crops found in Oaxaca and other MX states
GM crops illegal
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Genetic information moves, and is
self-replicating.
GM crops found in Oaxaca and other MX states
GM crops illegal
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Monsanto's is one of the largest sellers of GMO's
Monsanto Stock price
http//research.scottrade.com/public/stocks/snapsh
ot/snapshot.asp
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