-
proposes (but apparently never performs) an experiment in which a plant is weighed and then planted in a container containing a weighed amount of soil. After a period of growth, the final weights of plant and soil, as well as the total weight of water applied, are determined and compared to the initial values. He speculates this will demonstrate that the mass of the plant was derived from water rather than soil.
-
performs the experiment proposed by Nicholas of Cusa nearly 200 years earlier. He concludes that the entire mass of the plant came from water, but ignores a very slight decrease in the weight of the soil.
-
finds that air which has been made "noxious" by the breathing of animals or burning of a candle can be restored (i.e., made to support breathing or combustion again) by the presence of a green plant. He isolates the gas later identified as oxygen.
-
begins to investigate and later names oxygen. He recognizes that it is consumed in both animal respiration and combustion. His work discredits the theory of "phlogiston," a hypothetical substance then believed to be emitted during respiration or combustion, and lays the foundations of modern chemistry.
-
discovers that only the green parts of plants release oxygen and that this occurs only when they are illuminated by sunlight.
-
demonstrates that green plants take in carbon dioxide from the air and emit oxygen under the influence of sunlight.
-
shows that the carbon assimilated from atmospheric carbon dioxide cannot fully account for the increase in dry weight of a plant. He hypothesized that the additional weight was derived from water. At this point, therefore, the basic equation of photosynthesis was established.
-
give the name "chlorophyll" to the green pigment in plants.
-
proposes that the sun is the ultimate source of energy utilized by living organisms, and introduces the concept that photosynthesis is a conversion of light energy into chemical energy.
-
demonstrates light-dependent starch formation in chloroplasts.
-
makes accurate quantitative measurements of carbon dioxide uptake and oxygen production, a step leading to a balanced equation for photosynthesis: 6CO2 + 12H2O + light energy ----> C6H12O6 + 6O2 + 6H2O