Today:

Water Stress

and

Genetically Modifying Plants

Fig 37.11

Water moves from the ground through roots into the shoot and out stomata in the leaves.

What happened to this root?

Flooding, constant submersion… Why would the plant respond like this?

Stomata control entry of CO2 and exit of H2O from plant leaves

Stomata

Fig 30.10

What about when water is scarce?

Fig 37.16

Structural adaptations of a plant that grows in an arid environment

Oleander

Structural adaptations of a plant that grows in an arid environment:

•Thick cuticle

•Thick epidermis

•Recessed stomata

Oleander

Fig 37.16

Stomata density can change depending on the environment. Typically ~200-300/mm2

Individual plants can change stomata number to adjust for changes in the environment.

Only mature leaves exposed to high CO2

New leaves develop with fewer stomata

JA Lake et al (10 May 2001) Nature 411, 154

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

Changes in precipitation 1900-2000

Irrigating crops eventually leads to increased soil salinity

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.html

Human resource production and use

http://www.earth-policy.org/Indicators/Grain/2006.htm

Worldwide Grain Production per Person

http://www.earth-policy.org/Indicators/Grain/2006.htm

Land use in USA, 1997

from Teosinte MaizeBy artificial selection that began ~10,000 years ago.

Hunter-Gatherer

Agricultural

Industrial

Genetic Engineering: Direct manipulation of DNA

We can now insert new genes or modify existing genes of plants

Agrobacterium infect plants, inserting some of their DNA into the plants genome. Fig 19.17

Fig 19.17

Agrobacterium infect plants, inserting some of their DNA into the plants genome.

Fig 19.17After inserting a gene into the Agrobacteria, they will insert that gene into the plant's DNA.

Mil

lion

s of

Hec

tare

s

Texas =70 ha

Global area planted with GM crops

http://www.gmo-compass.org/eng/agri_biotechnology/gmo_planting/257.global_gm_planting_2006.html

The agricultural release of genetically modified organisms is the largest scale

experiment that has ever been performed.

Why Change a Plant’s 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

Tbl 19.5

% o

f T

otal

US

Acr

esCommon GM Crops in the U.S.

http://blog.wired.com/

wiredscience/2007/09/

monsanto-is-hap.html

Are Genetically Modifying Plants Safe?

Human impacts:

Dead zone in Gulf of

Mexico from

Mississippi River

http://blog.nola.com/times-picayune/2007/06/despite_promises_to_fix_it_the.html

Pollen is easily transferred from plant to plant, and to related species.

GM crops illegal

GM crops found in Oaxaca and other MX states

Genetic information moves.

GM crops illegal

GM crops found in Oaxaca and other MX states

Genetic information moves, and is self-replicating.

Monsanto's is one of the largest sellers of GMO's

Monsanto Stock price

http://research.scottrade.com/public/stocks/snapshot/snapshot.asp

Next:

Animals