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PHOTOSYNTHESIS

The Development of Ideas

     
Hales 1727 Plants took their nourishment in part from the atmosphere.
Light energy participated in this process.
Priestley 1771 Green plants "renewed" air that was made "bad" by breathing animals or burning candles
"Renewed" air = oxygen
"Bad" air = carbon dioxide
     
At this time the composition of the atmosphere was being revealed and the gases in it were being discovered.
O2 Scheele
and
Priestley		 1773

1774
CO2 Black 1777
N2 Rutherford 1772
The composition of air Lavoisier

 

 1774
     
Ingenhousz 1779 Light is necessary for the production of O2 by plants
("Plants should be removed from the house at night")
Senebier 1782 Plants breathe like animals in the dark
De Saussure 1804 Quantitative measurements of photosynthesis.

Mass gain by plants through growth > Mass of CO2 absorbed – Mass of O2 released
The difference was attributed to water.
Sachs 1864 Observed the growth of starch grains in illuminated chloroplasts.
Classic experiment: Leaf exposed to light with certain parts covered.
In the exposed parts starch was produced
In the covered parts starch was absent.
Therefore:
Engelmann 1894 Experiment 1 : Light, Chlorophyll and Photosynthesis (link opens in new window)
Experiment 2 : Spirogyra filamentous alga + motile oxygen sensitive bacteria (link opens in new window)
Blackman 1920s Experiment 1: Light Intensity v Temperature (link opens in new window)
Experiment 2: Light Intensity and CO2 Concentration (link opens in new window)

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© Paul Billiet 2009