Photosynthesis Sci 190 E

Transcription

1 Photosynthesis Sci 190 E Lecture 13 photo-synthesis building by light Plants Algae Bacteria light CO 2 + H 2 O (CH 2 O) + O 2 1

2 Photosynthesis: main source of energy Photosynthesis: Annually fixes tons of carbon stores kj of energy Equivalent to 30,000 GW power plant Fossil fuel: coal, oil, gas Annual energy consumption in 2002 Year 2002 US (kj) World (kj) Petroleum Gas Coal Hydroelectric ~1/3 of total photosynthesis (10 18 kj) Nuclear electric Geo, solar, wind Total Sunlight falling on Earth surface is ~ kj/year (~1 kw/m 2 ) 2

3 Carbon dioxide emission All of oxygen in the atmosphere was produced by photosynthesis! Photosynthesis annually fixes ~ tons of carbon Using gas, coal, oil as energy source reverses natural process, burns oxygen and emits CO 2 ( green house effect ) Year 2002 Carbon emission: USA ton World 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 3

4 Discovery of photosynthesis: van Helmont Joean Baptista van Helmont Belgian physician Pioneer chemist Willow experiment: 5 lb 169 lb lb of dry soil 5 years rainwater only 200 lb - 2 ounces of dry soil Conclusion: 164 pounds of wood, bark, and roots, arose out of water only. Discovery of photosynthesis: van Helmont Joean Baptista van Helmont Hypothesis: Water is the only nutrient for plant growth 4

5 Discovery of photosynthesis: John Woodward Physician and geologist, Cambridge University 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 methods End of the 17th century: invention of microscope 1665: Published Micrographia Hooke s microscope Robert Hooke drawing of cells in cork Hooke was the first to observe cells 5

6 Discovery of photosynthesis: Microscope Improvement of a microscope Anton Van Leeuwenhoek Lens Focus knob Sample holder 270x magnification! Sample translator Discovery of photosynthesis: Nehemiah Grew 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. 6

7 Discovery of photosynthesis: Stephen Hales English physiologist, chemist Father of plant physiology 1727: published Vegetable Staticks the leaves and stems of plants do imbibe elastic air water mercury Was able to measure the sucking power of plants Discovery of photosynthesis: J. Priestley Joseph Priestley Never took any science course Minister in a small church in Leeds 1766: met Benjamin Franklin in London became interested in science 1767: graphite conducts electricity published The history of electricity 1770: eraser Carbon dioxide, soda 1772: elected to French Academy of Sciences 7

8 Discovery of photosynthesis: Priestley s experiments 1. Candle in an enclosed space burns out 2. Mouse in an enclosed space suffocates Discovery of photosynthesis: Priestley s 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 of all 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 8

9 Discovery of photosynthesis: Priestley s experiments 3. Candle and mint plant 27 days 4. Mouse and mint plant 5. Mouse needs plant Plant needs mouse Priestley s conclusions 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 1782: publishes History of Corruptions of Christianity book was officially burned in his home and church were burned (support of American and French revolutions) moved to US 9

10 Discovery of photosynthesis: Antoine Lavoisier Wealthy family 1773: Repeated Priestley s experiments Burning = combining with oxygen! named in 1779 acid-former 1783: Proved phlogiston theory to be wrong 1785: The Law of Conservation of Mass 1794: executed (guillotine) by revolutionists ("The Republic has no use for scientists. ) Paris News, May Discovery of photosynthesis: Jan Ingenhousz born in Breda, Netherlands court physician to Austrian Empress Maria Theresa Heard of Priestley s experiments Performed >500 experiments : "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!

11 Discovery of photosynthesis: Jean Senebier 1782 experiments: Leaves submerged in carbonated water produce oxygen Even 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 11

12 Discovery of photosynthesis: Julius Robert von Mayer German surgeon, interested in physics One of the formulators of laws of thermodynamics: Energy conservation law 1842: "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: chlorophyll 1817: French scientists Pelletier and Caventou isolated green pigment of leaves and called it chlorophyll chloros - green phyllon - leave (Greek) 1864: Julius Sachs demonstrated that carbohydrates are produced in photosynthesis in parts that contain chlorophyll : Theodore Engelman determined that chlorophylls are key pigments in green algae, and that red and blue light were the most active in generating oxygen Connection with physics: Engelman used prism spectrometer introduced in 19th century and modified by Bunsen and Kirchhoff 12

13 Discovery of photosynthesis: mechanism 19th century: Photosynthesis converts energy of light into chemical energy by synthesizing carbohydrates using mostly water and CO 2. 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 13