A Photosynthetic Timeline
1782, Jean Senebier
-demonstrated that green plants take in carbon dioxide from the air and emit oxygen under the influence of sunlight
-showed that CO2 was the "fixed" or "injured" air and that it was taken up by plants in photosynthesis¹
1774 Antoine Lavoisier
-began to investigate oxygen
-recognized the use of oxygen in both animal respiration and combustion
-discovered the concept of oxidation; reasoned that plants got food either from water and a little soil, or from the air¹
-discovered that only the green parts of plants release oxygen only occurring in sunlight
- discovered that light plays a major role in photosynthesis
-the first person to show that light is essential to the plant process that somehow purifies air fouled by candles or animals
- His experiment: he put an unlit plant and a candle into a transparent closed space. He allowed the system to stand in sunlight for two or three days assuring that the air inside was pure enough to support a candle flame. He then covered the closed space with a black cloth and let it remain covered for several days. When he tried to light the candle it would not light
-concluded that the plant must have ‘breathed’, fouling the air, in order to purify the air plants need light¹
1779 Jan Ingenhousz
1771 Joseph Priestley
-discovered that plants produced oxygen
-found that air which has been made "toxic" by the breathing of animals or burning of a candle can be restored in the presence of a green plant
-put a sprig of mint into a transparent closed space with a candle that burned out the air until it went out, he relit the extinguished candle again after 27 days and it burned perfectly well in the air that previously would not support it.¹
-proposed that plant leaves probably took in nourishment from the air, and that light may also be involved
-published Vegetable Staticks (Vegetable Physics)
-In his book, Hales described many investigations of the flow of sap in roots and stems of plants and the evaporation of water from their leaves
-was not successful in showing that plants absorbed air due to the fact that he didn’t realize plants quickly give off another gas as quickly as they absorbed the air needed for nutrition¹
1727 Stephen Hales
1804 Nicolas de Saussure
-demonstrated that the carbon conformed from atmospheric carbon dioxide cannot fully account for the increase in dry weight of a plant
-hypothesized that the additional weight was derived from water
-basic equation of photosynthesis was established; a process in which a green plant illuminated by sunlight takes in carbon dioxide and water and converts them into organic material and oxygen¹
1845 Julius Robert von Mayer
-proposed that the sun is the ultimate source of energy utilized by living organisms, and introduced the concept that photosynthesis is a conversion of light energy into chemical energy¹
1862 Julius von Sachs
-demonstrated light-dependent starch formation in chloroplasts.
- proved that chlorophyll is involved in photosynthesis¹
1864 Jean Baptiste Boussingault
-made accurate quantitative measurements of carbon dioxide uptake and oxygen production; lead to the balanced equation for photosynthesis: 6CO2 + 12H2O + light energy ----> C6H12O6 + 6O2 + 6H2O
1883 Thomas Engelmann
-performed experiment revealing which wavelengths worked best for photosynthesis
-found that motile aerobic bacteria collect near the portions illuminated by red and blue wavelengths¹