Interplay of Photosynthetic Mechanisms, Zea Mays, Light

and Climate ChangeBy Matt Carity and John Miller

Presentation Overview

• History/Explanation of Agriculture• Negative Impacts of Agriculture• How Agriculture affects the climate• Evolution of Corn and its impact on Civilization• Data/Methods used in corn deductions (i.e. constants, CO2/plant

correlations)• World Overview of Corn Production/Distribution• Regional (Southwestern Ohio) overview of corn production

On THIS date in agricultural history…• 5,700 YA in what is today NW Iran, smelting of copper-oxide ores into

metallic copper provided breakthroughs. (Goudie, 19)• 5,078 years ago: advent of irrigation for agriculture (19)• Domestication of animals allows for farmers to use plows… (enter

mechanization of agriculture) (19)• Plow: 5000 years ago. Used in Mesopotamia, Assyria, and Egypt.• Plow marks in Avebury, England have been dated at 3,000 BC

• Wheeled cart: allows for transport of products (19)• First produced in the Near East in the 4th millennium BC and spread

during the 3rd millennium (20)• 16th and 17th centuries: perfection of sea-going ships provides industrial

and economic transformation (25)• Late 18th century: advent of steam engine and internal combustion engine

(late 19th century) increased access, lessening reliance on animals, wind, and water. (26)

History/Explanation of Agriculture

• ag-ri-cul-ture: n. The science, art, and business of cultivating soil, producing crops, and raising livestock; farming

Source: Webster’s Dictionary

History/Explanation of Agriculture

• Holocene (10kya): domestication rather than gathering of food plants.

• Domestication reduces space required for sustaining each individual by a factor of at least 500 (Sears, 1957:54) [qtd. In Goudie 15]

Domestication vs. Cultivation• Cultivation: “deliberate sowing or… management and entails plants

which do not necessarily differ genetically from wild populations of the same species.”

• Domestication: “…results in genetic change brought about through conscious or unconscious human selection. …creates plants that differ morphologically from their wild relatives and which may be dependent on humans for survival.“

“Domesticated plants are cultivated, but cultivated plants may or may not be domesticated.”

Source: Goudie, Impact pg. 16

Negative Impacts of AgricultureThere are a number of possible ways in which modern day agriculture can

negatively influence the surrounding environment. Some examples of this are by:

• Air pollution from machinery• Fertilizer runoff (i.e. soil contamination, eutrophication)• Soil Compaction• Soil Erosion• Increased sedimentation in reservoirs• Desertification• Groundwater withdrawal and contamination• Increased Biomass (concentration of nutrients in material rather than soil)• Natural Habitat destruction (water rerouted/ windbreaks destroyed-impact weather)• Increased albedo (in some cases) • Decreased/Altered biodiversity• Provocation of insects/pest into areas.

How Agriculture Affects Climate

• Increased amounts of carbon dioxide in atmosphere may act as fertilizer to some plants (Nilsson, 109) by increasing photosynthetic rate and rate of plant growth. (111)

• 6CO2 + 6H2O C6H12O6 + 6O2

Water Use Efficiency with Increased CO2

• Increasing carbon dioxide allows for “more efficient” water use:– C3 plants (wheat, rice) take direct advantage of

increased carbon dioxide– C4 plants, though (like corn), benefit less– CAM plants remain unaffected (111)

C3, C4, & CAM PlantsC3 PLANTS• Competition between

carbon dioxide and oxygen…

• You can either trap and store carbon, or burn it as fuel

• An increase in carbon dioxide tips the scale in favor of trapping

• Result: higher productivity and better (more numerous) yields (111, 112)

C4 and CAM PLANTS• No competition

between carbon dioxide and oxygen in photosynthesis (113)

Impacts on Climate and the Atmosphere

• Radiation of all wavelengths is partly absorbed and partly reflected.

• Albedo: proportion of energy reflected; a measure of ability of a surface to reflect radiation (Goudie, 315)

• No vegetation [deforestation or over-grazing] = very high albedo

• Plant covered = lower albedo (315)– Savannah grasslands = 14% – Deserts = 30% (Burroughs, 154)

• This could affect temperature levels (316)

R O Y G B I V

Light and Albedo

• Chloroplasts absorb specific wavelengths of light (680 and 700

• Light not absorbed is reflected• Darker colors absorb more light• Color of crop would be an indication of

photosynthesis success? (Dark crops more productive?)

Culmination of months of scientific research…

6CO2 + 6H2O C6H12O6 + 6O2

Effects of CO2 on Yields

• What effects will doubling the carbon dioxide concentration have on plants with differing photosynthetic mechanisms?– C3: Y = 10-50%

– C4: Y = 0-10%– CAM: Y = 0%*C3 weeds in C4 crops*

Evolution of Corn and its Impact on Humans

• Corn-Any of numerous cultivated forms of a widely grown, usually tall annual cereal grass (Zea mays) bearing grains or kernels on large ears. http://www.bartleby.com/61/51/C0645100.html. Believed to have originated from Tehuacan. (MacNeish, 1985)

• Believed by many botanists to have its ancestral roots as Teosinte, a Mexican grass, • Teosinte-((Zea mexicana or Euchlaena mexicana), tall, stout, annual grass of the

family Poaceae, native to Mexico. Teosinte is related to corn (maize) and grows in large clumps, with tassels (staminate flowers) like those of corn. http://search.eb.com/eb/article?eu=73591&tocid=0&query=teosinte&ct=

• Teosinte and modern corn (maize) are both comprised of 10 chromosomes.• Teosinte most distinguished from corn by a comparison of the two plant’s

morphology. – Teosinte composed of a small female flower, which develops into a two-ranked

‘ear’ from which five to 10 small, triangular to trapezoidal black seeds mature. Teosinte in general, is much smaller than today’s corn plant.

– Teosinte has very strong outer layer to protect it as it moves through digestive tracts to be distributed.

– Teosinte is much more prone to disemmination than corn.

Teosinte vs. Modern Corn

http://images.google.com/imgres?imgurl=www.aenews.wsu.edu/May02AENews/MexiCorn/Figure1.jpg&imgrefurl=http://www.aenews.wsu.edu/May02AENews/May02AENews.htm&h=308&w=576&sz=30&tbnid=MvSfh1lKXxwJ:&tbnh=70&tbnw=130&prev=/images%3Fq%3Dteosinte%26start%3D40%26hl%3Den%26lr%3D%26ie%3DUTF-8%26oe%3DUTF-8%26safe%3Doff%26sa%3DN

Evolution of Corn and its Impact on HumansThe domestication of corn began at least 7,000 years ago in Mesoamerica, probably with that of teosinte (

http://cimnts.mnhn.fr/Evolution/UkGge.nsf/0/fd28c04824f59934802565bb006d7a95?OpenDocument) From this point, various varieties of corn took shape and were cultivated to create the varieties we have today.

The Aztecs: An empire built around maizeMaize was a revered and intergral part of culture: Many stories, wars, feasts, poetry, etc. revolved around theme of Maize.

Able to be grown in high plateaus as well as lowlands of Mesoamerica. Also capable of yielding more than one harvest a year in many parts.

Thought to have been the motive behind Aztec conquest of more temperate zones in which maize could be grown.

Provided a hardy, nutritious foodstuff which was also very practical due to its ability to be stored relatively easy. This acted to assure the effects of famine were less devastating.

Consistent yields and length of growth period provided sustaining rations as well as promoted sedintary living.

Cultivation of maize allowed individuals to focus less on hunting/gathering, and provided individuals with more free time to learn specialized trades involving manufacturing, textiles, and crafts , and to establish military and governing systems. (Culture Sketches)

After the discovery of the Americas, corn found its way into various cultures and corners of the world. It has helped to sustain many cultures over time and has been cultivated and modified to create the varieties we have today.

Currently, we have numerous varieties of corn, such as Bt corn, which has been genetically modified to resist pests. As of now, there are still questions regarding whether genetically modified foods such as Bt corn have adverse side effects or whether they are safe for consumption. (http://www.uky.edu/Agriculture/Entomology/entfacts/fldcrops/ef130.htm)

Not only is corn a food source, but research is being done to see how it may also be a resource in creating plastics, clothing, fuels, etc.

Albedo and Corn• The reflectivity is only about 0.05 for wavelengths shorter

than 0.60 microns for maize, but 0.32 for maize at the wavelength of green light (0.60-0.63 microns). The reflectivity is lower again in orange and red (0.64-0.71 microns), but at 0.75 microns it exceeds 0.50 for most plants. (file:///C:/DOCUME~1/DEFAULT/LOCALS~1/TEMP/Spectral%20variation%20of%20albedo.html)

More Data Concerning CornThe recommended final plant populations for corn range between 18,000 to 30,000 plants per acre, depending on soil yield potential, hybrid, presence of irrigation, and row width.

Around 80 percent or more of corn producers in the United States using 30-inch or narrower planting equipment

Actual planting rates of corn should exceed expected final stand by 5 to 15 percent to allow for germination failure and seedling mortality. (IS1548 Corn Plant Population)

Worldwide Corn

Production

Worldwide Overview of Corn Production/Distribution

Overall 23.5 billion bushels of corn were harvested in 2002.

United States: 9.5 billion bushels in 2002

United States harvest 40% of the worlds corn crop.

National Corn Yield

Regional (Southwestern Ohio) Overview of Corn Production

Corn Crop Yield in 5-year Incriments (1997 Being Most Recent) from 1980-1997 for Twelve Selected Counties Comprising Southwestern Ohio

0

2,000,000

4,000,000

6,000,000

8,000,000

10,000,000

12,000,000

14,000,000

16,000,000

Adams HighlandFayetteBrownClintonGreeneClermontWarren

MontgomeryHamilton

ButlerPreble

Counties

Crop Production (Bushels)

1980

19851990

19951997

Conclusions

• C3 benefit more from carbon dioxide increases

• Dark crops photosynthesize more effectively

• Less heat is radiated from a dark crop