Photosynthesis. How do plants grow?. Van Helmont - 1648. Joseph Priestley. Priestley – 1771 – plants restore “good quality” to air. Jan Ingenhousz – 1796 – plants only restore good quality to air in the presence of light. Water is source of oxygen released during photosynthesis.
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Van Helmont - 1648
Van Niel was studying the activities of photosynthetic bacteria - he found that purple sulfur bacteria reduce carbon to carbohydrates but do not release oxygen; instead the purple sulfur bacteria use hydrogen sulfide in their photosynthesis - so for them the reaction is as follows:
CO2 + 2H2S + light energy =>(CH2O) + H2O + 2S
Van Niel then generalized this to the following reaction for all photosynthetic activity
CO2 + 2H2A + light energy=>(CH2O) + H2O +2A
C.B. van Niel
One of three things may happen to that energy:
1. the energy may be dissipated as heat
2. the energy may be re-emitted almost instantly as light of a longer wavelength - this is called fluorescence
3. the energy may be captured by the formation of a chemical bond - as in photosynthesis
6CO2 + 12NADPH + 12H+ + 18ATP =>
C6H12O6 (GLUCOSE) + 12NADP+ + 18ADP + 18 Pi + 6H2O