Historical Perspective

• Jan Van Helmont partially discovered photosynthesis in 1648, when he planted a willow tree in plant and found that it grew in size five years later
• Joseph Priestly discovered oxygen in 1774. His experiments also demonstrated that plants produce oxygen and animals use this to produce carbon dioxide, and that light is essential for photosynthesis
• Jan Ingenhousz confirmed Priestley's work and showed that light is necessary for plants to release oxygen, and that only the green parts of the plants can photosynthesize
• Lavoisier suggested that plants absorb carbon from carbon dioxide, and the one to name the oxygen and hydrogen, and wrote the first textbook of modern chemistry
• T.W Englishmann was the first to conclude that red and blue light are the most effective for producing oxygen in photosynthesis
• Julius Sachs reported that chlorophyll, a photosynthetic pigment, occurs in the chloroplasts of plants, and that photosynthesis forms carbohydrates only with the presence of the light
• Van Niel claimed that the oxygen released during photosynthesis comes from the water not in the carbon dioxide
• Robin Hill discovered the Hill reaction, which is the portion of the light reactions in which electrons from water are transferred to an electron acceptor, reducing the acceptor, The evidence for this was the production of oxygen even when carbon dioxide is absent