1. Unit 2: Metabolic Processes History
SBI4U – Ms. Richardson

2. History 1600’s: J.B. Van Helmont
Compared soil mass to that of a growing willow tree
Demonstrated that soil nutrients were not responsible for growth of plants
Concluded water absorption was responsible

3. History 1771, Joseph Priestly
Discovered gases play a role in photosynthesis
“injured air” hypothesis:
Placed lit candle in bell jar
candle goes out (injured air)
Placed live mint plant + lit candle in bell jar
after 10 days, plant “restores” air and candle burns again

4. History 1796, Jan Ingenhousz Confirmed Priestley’s findings
Demonstrated that light was essential to photosynthesis
Defined “injured air” as CO2
Proposed O2 is produced from splitting of CO2

5. History
1882, T.W Engelmann
Used Spirogyra alga to determine which colours of visible light were most effective in photosynthesis
Demonstrated that chloroplasts respond to red and blue light

6. History
1905, F.F Blackman
Measured effect of change in light intensity and temperature on CO2 concentrations
Demonstrated:
At low light intensity:
Rate of photosynthesis can be increased by increasing light intensity but not temperature
At high light intensity:
Rate of photosynthesis can be increased by increasing temperature but not light intensity
Concluded there are 2 stages of photosynthesis:
Light dependent (photochemical)
Light independent (biochemical)

7. History 1930’s, C.B. Van Niel 1938, S.M Ruben, M. Kamen
Used purple sulfur bacteria to demonstrate O2 is produced by splitting water, not CO2
Proposed the following:
CO2 + 2H2S + light  carbohydrate + H2O + 2S
1938, S.M Ruben, M. Kamen
Used radioactivity to confirm Van Niel’s findings