Yes, discussions this week;
Exams back Friday

CB 36.2
Water and minerals move up from the ground in xylem,
Sugars move down, up and/or laterally via phloem.

CB 36.13
What moves the water through the xylem?
Transpiration,
Adhesion,
Cohesion, and
Tension

Stomata on the underside of a leaf

Water conducting cells of Xylem: vessels and tracheids
(types of sclerenchyma)
CB 35.9
100
 m

CB 35.12 and .13
In roots the vascular bundle is in the center

Phloem on outside
Radially arranged vascular bundle in a stem
CB 35.16
Xylem on inside

water transport limits plant growth

More xylem is needed for more water transport: secondary growth phloem xylem

CB 35.10
Primary vs. secondary growth

Primary growth in a stem
CB 35.18

Secondary growth: a vascular meristem
(cambium) forms between the xylem and phloem
CB 35.18

Secondary growth: new xylem to the inside, new phloem to the outside
CB 35.18

Secondary xylem
(wood) and phloem

Some additional cells help form the bark and fill in the increasing circumference
CB 35.20

Xylem is tough, and full of lignin- inhibits the ability to use plants to produce biofuels phloem xylem

U.S. Energy use in 2005
Units are in quads; 1 quad =
1015 British thermal units =
1.055 exajoules http://www.sciencemag.org/sciext/sustainability/ Science 9 February 2007:Vol. 315. no. 5813, pp. 796 - 798

~28% of U.S. energy is used in transportation http://www.eia.doe.gov/kids/energyfacts/uses/transportation.html
U.S. Department of Energy, Transportation Energy Data Book: Edition 26-2007.

In 2005, there were almost 239 million vehicles (cars, buses, and trucks) in the United
States.
http://www.eia.doe.gov/kids/energyfacts/uses/transportation.html
U.S. Department of Energy, Transportation Energy Data Book: Edition 26-2007.

Automobiles, motorcycles, trucks, and buses drove nearly 3.0 trillion miles in 2005. That’s almost 1/12 th the distance to the nearest (non-sun) star. It’s like driving to the sun and back 13,440 times.
Transportation fuel use http://www.eia.doe.gov/kids/energyfacts/uses/transport ation.html
U.S. Department of Energy, Transportation
Energy Data Book: Edition 26-2007.

Vehicle Energy Use http://www.eia.doe.gov/kids/energyfacts/uses/transportation.html
U.S. Department of Energy, Transportation Energy Data Book:
Edition 26-2007.

World Primary Energy Supply 2004 http://www.sciencemag.org/sciext/sustainability/

Research money spent on alternative energy http://www.sciencemag.org/sciext/sustainability/
Science 9 February 2007: Vol. 315. no. 5813, pp.
782 - 783

Ethanol vs Gasoline prices http://www.sciencemag.org/sciext/sustainability/

Biofuel production http://www.sciencemag.org/sciext/sustainability/

CB 5.7
Cellulose, sugars as structural support

CB 5.8
The major component of plant cell walls is cellulose

Fermentation: break down sugar to ethanol

http://www.iogen.ca/images/m1
_fuel_cycle2.jpg

Lignin: a complex branched, aromatic polymer

Lignin cross-links cellulose fibers and makes secondary walls waterproof http://www.ccrc.uga.edu/~mao/intro/ouline.htm

Lignin removal is necessary for cellulose processing
Nature Biotechnology 20, 557 - 558 (2002)

Treatment efficiencies of untreated transgenic biomass are comparable to that of unmodified biomass subjected to pretreatment
Loosening lignin's grip on biofuel production Clint Chapple, Michael Ladisch & Rick Meilan Nature Biotechnology 25, 746 - 748 (2007)

Research is ongoing to produce woody and non-woody plants with decreased lignin to improve the efficiency of biofuel production xylem

Yes, discussions this week;
Exams back Friday