-
350 BCE
Aristotle
Aristotle proposes that plants, like animals, require food. After 2000 years, Priestley anticipates later by asserting that plants do not require animals but animals require plants. -
Period: 350 BCE to
DISCOVERY OF PHOTOSYNTHESIS
A timeline of the key events that led to scientists developing an understanding of photosynthesis. -
300 BCE
Theophrastus
Theophrastus wrote that plants obtain their nourishment through the roots. -
Jun 20, 1450
Nicolas of Cusa
Nicholas of Cusa proposes an experiment where he can speculate the demonstration that the mass of the plant was derived from water rather than soil. The experiment was about 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. -
Jan Baptist Van Helmont
He conducted experiments which led him to conclude that the entire mass of the plant came from water, but ignores a very slight decrease in the weight of the soil. Jean Baptiste van Helmont performs the experiment proposed by Nicholas of Cusa nearly 200 years earlier. -
Edme Mariotte
Proposes the idea that plants obtain part of their nourishment from the atmosphere -
John Woodward
Discovered that most of the water absorbed by plants are released into the atmosphere which opposed Van Helmont’s conclusion that plants gain most of their weight from water. -
Stephen Hales
Stephen Hales writes that plant leaves "very probably" take in nourishment from the air, and that light may also be involved. -
Charles Bonnet
Charles Bonnet observes the emission of gas bubbles by a submerged illuminated leaf. -
Joseph Priestley
Joseph Priestly discovered a gas, dubbed "dephlogisticated air" by focusing solar rays on mercuric oxide. This gas was later names "oxygen" -
Antoine Lavoisier
Antoine Lavoisier 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. -
Jan Ingen-Housz
Jan Ingenhousz discovers that only the green parts of plants release oxygen and that this occurs only when they are illuminated by sunlight. -
Jean Senebier
Jean Senebier demonstrates that green plants take in carbon dioxide from the air and emit oxygen under the influence of sunlight. -
Domenico Comparetti
Comparetti observes green granules in plant tissues, later identified as chloroplasts. -
Nicolas de Saussure
Nicolas de Saussure 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. It was understood as a process in which a green plant illuminated by sunlight takes in carbon dioxide and water and converts them into organic material and oxygen. -
Pierre Joseph Pelletier and Joseph Bienaime Caventou
Pierre Joseph Pelletier and Joseph Bienaime Caventou give the name "chlorophyll" to the green pigment in plants. -
Matthias Schleiden
Matthias Schleiden postulates that the water molecule is split during photosynthesis. -
Hugo von Mohl
Hugo von Mohl makes detailed observations of the structure of chloroplasts. -
Julius Robert
Julius Robert von Mayer 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. -
Julius von Sachs
Julius von Sachs demonstrates light-dependent starch formation in chloroplasts. -
Jean Baptiste Boussingault
Jean Baptiste Boussingault 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 -
Emil Godlewski
Emil Godlewski confirms that atmospheric carbon dioxide is the source of carbon in photosynthesis by showing that starch formation in illuminated leaves depends upon the presence of carbon dioxide. -
Arthur Meyer
Arthur Meyer describes the chloroplast grana. -
Theodor Wilhelm Engelmann
Theodor Wilhelm Engelmann illuminates a filamentous alga with light dispersed through a prism. He finds that motile aerobic bacteria congregate near the portions illuminated by red and blue wavelengths, thus producing the first action spectrum for photosynthetic oxygen evolution. -
Charles Barnes
Charles Barnes suggests that the process by which illuminated green plants manufacture carbon compounds be called either "photosyntax" or "photosynthesis." Although Barnes prefers the former, "photosynthesis" is adopted into common usage. -
F. F. Blackman
F. F. Blackman develops the concept of limiting factors, showing that photosynthesis consists of two types of reactions: a rapid light-dependent photochemical process and a slower temperature-dependent biochemical process. These are later termed "light reactions" and "dark reactions," respectively. -
Richard Willstatter and Arthur Stoll
Richard Willstatter and Arthur Stoll publish studies on the structure and chemistry of chlorophyll. Willstatter awarded Nobel Prize, 1915. -
Robert (Robin) Hill
Robert (Robin) Hill demonstrates that in the presence of an artificial electron acceptor isolated chloroplasts can evolve oxygen in the absence of carbon dioxide. -
Cornelis van Niel
Cornelis van Niel publishes a summary of his work showing that photosynthetic bacteria which use H2S as an electron donor produce elemental sulfur instead of oxygen. He suggests by analogy that the O2 released in plant photosynthesis is derived from H2O rather than CO2. -
Samuel Ruben and Martin Kaman
Samuel Ruben and Martin Kaman use water labeled with the heavy isotope 18O to confirm that the oxygen produced in photosynthesis comes from H2O. -
Daniel Arnon
Daniel Arnon demonstrates light-dependent ATP formation in chloroplasts. -
Daniel Arnon
Daniel Arnon demonstrates that isolated chloroplasts are capable of carrying out complete photosynthesis. -
Melvin Calvin
Melvin Calvin and coworkers use radioactively labeled 14CO2 to elucidate the pathway of carbon assimilation in photosynthesis. Calvin awarded Nobel Prize in 1961. -
Robert Emerson
Robert Emerson describes the "red drop" and "enhancement" effects, the first indication that the light reactions of photosynthesis consist of two separate photochemical systems. -
Robert Woodward
Robert Woodward synthesizes chlorophyll -
Robin Hill and Fay Bendall
Robin Hill and Fay Bendall, based on the work of Emerson and others, propose the "Z scheme" model for the photosynthetic light reactions. According to this model, the light reactions consist of two separate photosystems operating in tandem, each activated by slightly different wavelengths of light. -
Louis Duysens
Louis Duysens provides evidence in support of the Z scheme by demonstrating that exposure to alternating wavelengths of light causes cytochrome f to switch between oxidized and reduced states. -
Roderick Clayton
Roderick Clayton isolates reaction center complexes. -
Bessel Kok
Bessel Kok proposes the "S-states" model of charge accumulation to explain the stepwise oxidation of H2O and release of O2. -
Hans Deisenhofer, Hartmut Michel, and Robert Huber
Hans Deisenhofer, Hartmut Michel, and Robert Huber crystallize the photosynthetic reaction center from a purple bacterium and use X-ray diffraction techniques to determine its detailed structure. -
Koichi Kobayashi
With the help of coworkers, identified a chlorophyll a derivative which is the primary electron acceptor of green sulfur bacteria. -
Junko Yano, Vittal Yachandra, and co-workers
Junko Yano, Vittal Yachandra, and co-workers determine the structure of the manganese-calcium water-splitting complex of Photosystem II.
