Exam #2 F 4/1 (bring cheat sheet) Q&A Th 3/31 TBA Today: Material Transport

CB 36.2 Plants transport water, sugar, minerals, hormones, etc through the vascular system comprised of xylem and phloem

Water travels from ground out through leaves via xylem CB 36.2

Sunlight powers photosynthesis and these sugars are transported via phloem CB 36.2

Phloem transport is from source to sink.

Sugar is loaded at sources and unloaded at sinks... consuming ATP (energy) source: leaf sink: root, flower, emerging leaf etc… CB 36.20

Source and sink locations vary...

The direction of Phloem transport is versatile.

Water travels from ground out through leaves via xylem CB 36.2

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

Stomata control entry of CO 2 and exit of H 2 O from plant leaves Stomata CB 36.14

Stomata on the underside of a leaf

CB Guard cells regulate the opening of stomata

CB Water is pulled up through the xylem: Transpiration, Adhesion, Cohesion, and Tension

water transport limits plant growth

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

CB Primary vs. secondary growth

CB Primary growth in a stem

Secondary growth: a vascular meristem (cambium) forms between the xylem and phloem CB 35.19

Secondary growth: new xylem to the inside, new phloem to the outside CB 35.19

Secondary xylem (wood) and phloem

The major component of plant cell walls is cellulose

xylem phloem Xylem is made mostly of cellulose, but also lignin

Lignin: a complex branched, aromatic polymer

Lignin cross-links cellulose fibers and makes xylem waterproof

Cellulose, sugars as structural support

Fermentation: break down sugar to ethanol

_fuel_cycle2.jpg

Nature Biotechnology 20, (2002) Lignin removal is necessary for cellulose processing, and it is energy intensive

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

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

~28% of U.S. energy is used in transportation U.S. Department of Energy, Transportation Energy Data Book: Edition

In 2005, there were almost 239 million vehicles (cars, buses, and trucks) in the United States. U.S. Department of Energy, Transportation Energy Data Book: Edition

U.S. Department of Energy, Transportation Energy Data Book: Edition Vehicle Energy Use

Automobiles, motorcycles, trucks, and buses drove nearly 3.0 trillion miles in 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 ation.htmlhttp:// ation.html U.S. Department of Energy, Transportation Energy Data Book: Edition

World Primary Energy Supply

_fuel_cycle2.jpg

Biofuel production

Much of our Alternative Energy Research is in Biofuels

CB Human resource production and use Worldwide Grain Production per Person 7

World Grain Stocks as Days of Consumption

~60 percent of the world grain harvest is consumed as food, ~36 percent as feed, and ~3 percent as fuel. While the use of grain for food and feed grows by roughly 1 percent per year, that used for fuel is growing by over 20 percent per year.

Corn prices late 1999 – Nov

Corn prices Oct 2007-Nov om/

Increasing oil prices drive up potential profit, and cost of food crops Cost of oil----Profitable cost of corn for ethanol $ $4/bushel $ $7/bushel $ $10/bushel Summer 2008 corn price: ~$8/bushel August '10 corn price: ~$4.00/bushel Current March '11 price: ~$6.90/bushel policy.org/Updates/2008/Update69.htm, policy.org/Updates/2008/Update69.htm

Whereas previous dramatic rises in world grain prices were weather-induced, this one is policy-induced and can be dealt with by policy adjustments. If the entire U.S. grain harvest were converted into ethanol, it would satisfy scarcely 18 percent of our automotive fuel needs.

Exam #2 F 4/1 (bring cheat sheet) Q&A Th 3/31 TBA Today: Material Transport