Sci 190 E Photosynthesis Lecture 13 - Purdue University
Transcript of Sci 190 E Photosynthesis Lecture 13 - Purdue University
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PhotosynthesisSci 190 ELecture 13
photo-synthesis – building by light
CO2 + H2O (CH2O) + O2light
PlantsAlgaeBacteria
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Photosynthesis: main source of energy
Photosynthesis:
• Annually fixes 1011 tons of carbon• stores 1018 kJ of energy
• Equivalent to 30,000 GW power plant• Fossil fuel: coal, oil, gas
Annual energy consumption in 2002
4.27 × 10171.08 × 1017Total
0.28 × 10170.01 × 1017Hydroelectric
0.28 × 10170.03 × 1017Nuclear electric
0.03 × 10170.003×1017Geo, solar, wind…
1.03 × 10170.25 × 1017Coal
1.00 × 10170.24 × 1017Gas
1.62 × 10170.45 × 1017Petroleum
World (kJ)US (kJ)Year 2002
http://www.eia.doe.gov/iea/overview.htmlhttp://www.cslforum.org/usa.htm
~1/3 of totalphotosynthesis(1018 kJ)
Sunlight falling on Earth surface is ~4 ×1021 kJ/year(~1 kW/m2)
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Carbon dioxide emission
Using gas, coal, oil as energy source reverses natural process, burns oxygen and emits CO2 (‘green house effect’)
All of oxygen in the atmosphere was produced by photosynthesis!
Photosynthesis annually fixes ~ 1011 tons of carbon
Year 2002Carbon emission:
USA 1.6 × 109 tonWorld 7 × 109 ton
History of photosynthesis research
Major advances in understanding photosynthesis (and biological systems in general) occur when new knowledge and techniques from other sciences (physics, chemistry…) are applied to biological systems
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169 lb
200 lb - 2 ounces of dry soil
Discovery of photosynthesis: van Helmont
http://mattson.creighton.edu/History_Gas_Chemistry/vanHelmont.html
1579-1644
Joean Baptista van Helmont
Belgian physicianPioneer chemist
“Willow” experiment:
200 lb of dry soil
5 lb
rainwater only5 years
Conclusion: 164 pounds of wood, bark, and roots, arose out of water only.
Discovery of photosynthesis: van Helmont
1579-1644
Joean Baptista van Helmont
http://www.howe.k12.ok.us/~jimaskew/botzo/botphoto.htm
Hypothesis: Water is the only nutrient for plant growth
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Discovery of photosynthesis: John Woodward
1665 - 1728
Physician and geologist, Cambridge University
http://www2.nsta.org/Energy/find/primer/primer2_5.html
One plant showed a mass gain of about 1 gram, while Woodward had added a total of almost 76,000 grams of water during the 77 days of plant growth.
Conclusion:• water was “drawn off and conveyed through the pores of the
leaves and exhaled into the atmosphere.”• “We may very reasonably infer, that Earth, and not Water is the
matter that constitutes Vegetables. … Water serves only for a Vehicle to the terrestrial Matter which forms Vegetables; and does not itself make any addition unto them.”
Need better experiment to control water consumption!
Discovery of photosynthesis: Microscope
Progress relies on experimental methodsEnd of the 17th century: invention of microscope
Robert Hooke
1635-1703
1665: Published “Micrographia”Hooke’s microscope
drawing of cells in cork
Hooke was the first to observe cells
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Discovery of photosynthesis: Microscope
Anton Van Leeuwenhoek
1632-1723
Improvement of a microscope
Focus knob
Sample translator
Sample holder
Lens
270x magnification!
Discovery of photosynthesis: Nehemiah Grew
1641 - 1712
English botanist
microscopic studies of the internal structure of plants in the 1670's:Leaves have many openings
“[T]he skins of at least many plants are formed with several orifices or passports, eithre for the better alveolation [evaporation] of superfluous sap, or the admission of air.”
http://www2.nsta.org/Energy/find/primer/primer2_6.html
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Discovery of photosynthesis: Stephen Hales
1677–1761
English physiologist, chemist“Father” of plant physiology
http://www.hcs.ohio-state.edu/hort/history/108.html
“the leaves and stems of plants do imbibe elastic air”
mercury
water
1727: published “Vegetable Staticks”
Was able to measure the ‘sucking’ power of plants
Discovery of photosynthesis: J. Priestley
1733 – 1804
Joseph Priestley • Never took any science course
• Minister in a small church in Leeds
• 1766: met Benjamin Franklin in Londonbecame interested in science
• 1767: graphite conducts electricitypublished “The history of electricity”
• 1770: eraser
• Carbon dioxide, soda
• 1772: elected to French Academy of Sciences
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Discovery of photosynthesis: Priestley’s 1771-1772 experiments
1. Candle in an enclosed space burns out
2. Mouse in an enclosed space suffocates
http://www2.nsta.org/Energy/find/primer/primer2_7.html
Discovery of photosynthesis: Priestley’s 1771-1772 experiments
Conclusions:• Air is consumed and somehow “injured”• “[A]n ordinary candle consumes … about a gallon [of air] in a
minute. Considering this amazing consumption of air, by fires ofall kinds, volcanoes, etc. it becomes a great object of … inquiry to ascertain what change is made in … the air by flame, and to discover what provision there is in nature for remedying the injury which the atmosphere receives …”
• Hypothesis: plants restore air
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Discovery of photosynthesis: Priestley’s 1771-1772 experiments
27 days
4. Mouse and mint plant 5. Mouse needs plantPlant needs mouse
3. Candle and mint plant
Priestley’s conclusions
1782: publishes “History of Corruptions of Christianity”book was officially burned in 1785
1791 - his home and church were burned (support of American and French revolutions)1794 - moved to US
Plants ‘repair’ air (produce oxygen)Burning ‘injures’ air (burns oxygen and produces carbon dioxide)
Drawback: he believed in ‘phlogiston theory’: every flammable substance contains phlogiston that is released into air by burning
phlogiston
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Discovery of photosynthesis: Antoine Lavoisier
1743 – 1794
http://en.wikipedia.org/wiki/Antoine_Lavoisier
Wealthy family
1773: Repeated Priestley’s experimentsBurning = combining with oxygen!
1783: Proved phlogiston theory to be wrong1785: The Law of Conservation of Mass
named in 1779‘acid-former’
1794: executed (guillotine) by revolutionists("The Republic has no use for scientists.“)Paris News, May 8 1794http://www.woodrow.org/teachers/ci/1992/Lavoisier.html
Discovery of photosynthesis: Jan Ingenhousz
1730-1799
born in Breda, Netherlands court physician to Austrian Empress Maria Theresa
Heard of Priestley’s experimentsPerformed >500 experiments
1779: "I observed that plants not only have the faculty to correct bad air in six to ten days, by growing in it...but that they perform this important office in a complete manner in a few hours; that this wonderful operation is by no means owing to the vegetation of the plant, but to the influence of light of the sun upon the plant".
Power of plants resides in the influence of sun light!
http://www.chm.bris.ac.uk/motm/chlorophyll/chlorophyll_h.htm
http://web.lemoyne.edu/~giunta/Ingenhousz.html
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Discovery of photosynthesis: Jean Senebier
1742–1809
http://www.aidh.org/Refug/GE_refug/31.htm
1782 experiments: Leaves submerged in carbonated water produce oxygenEven ground up leaves produce oxygen
Conclusions:- photosynthesis absorbs carbon dioxide and generates oxygen- it occurs in part of the plants that contain green pigment
Discovery of photosynthesis: Theodore de Saussure(Swiss chemist)
1804:gain in weight of a plant is the sum of the carbon absorbed by the plant in the form of carbon dioxide and water taken up by the plant roots and retained as plant matter.
Conclusion:- plants convert water, along with carbon dioxide from the air into dry matter in their food-making process
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Discovery of photosynthesis: Julius Robert von Mayer
http://www.usd.edu/phys/courses/phys300/gallery/clark/vonmayer.htmlhttp://www.cartage.org.lb/en/themes/Biographies/MainBiographies/M/MayerJR/1.html
1814-1878
German surgeon, interested in physics
One of the formulators of laws of thermodynamics: Energy conservation law1842: "Nature has put itself the problem of how to catch in flight light streaming to the Earth and to store the most elusive of all powers in rigid form. The plants take in one form of power, light; and produce another power, chemical difference."
Conclusion:Plants convert energy of light into chemical energy
Discovery of photosynthesis: chlorophyll1817: French scientists Pelletier and Caventou isolated green pigment of leaves and called it chlorophyll chloros - green
phyllon - leave (Greek)
1832-1897
1864: Julius Sachs demonstrated that carbohydrates are produced in photosynthesis in parts that contain chlorophyll
http://www2.nsta.org/energy/find/luminaries/sachs.html
1883: Theodore Engelman determined that chlorophylls are key pigments in green algae, and that red and blue light were the most active in generating oxygen
1843-1909
Connection with physics: Engelman used prism spectrometer introduced in 19th century and modified by Bunsen and Kirchhoff
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Discovery of photosynthesis: mechanism
19th century: Photosynthesis converts energy of light into chemical energy by synthesizing carbohydrates using mostly water and CO2.Open question: how can plants do it?
Major advances in understanding photosynthesis (and biological systems in general) occur when new knowledge and techniques from other sciences (physics, chemistry…) are applied to biological systems