Early Experiments of Photosynthesis

• Photosynthesis is a physico-chemical process. Green plants use light energy for the synthesis of organic matter like glucose.

• It is an enzyme regulated anabolic process. Photosynthesis is the basis of life on earth because it is the primary source of all types of  food on earth directly or indirectly.

• It is only a process to fix  atmospheric carbon dioxide and in turn it releases oxygen to maintain the  ecological balance. Besides carbon dioxide,

• Chlorophyll, sunlight is also  required for photosynthesis .The green part of the leaf is the main site of photosynthesis.

Jan Baptista van Helmont

• He provided a random concept that discovered the process of photosynthesis. He grew a willow tree in a weighted amount of soil.

• After five years, he observed that the weight of the willow tree had increased . The increase in weight of willow tree was more than his recorded data of  soil and minerals .

• He concluded that plant growth cannot only be due to minerals from the soil.

• He thought that the extra plant material had come from the water and carbon dioxide and plants accumulate some dry matter by process like photosynthesis.

Joseph Priestley

• He demonstrated  on the basis of his experiments the essential role of oxygen in growth of green plants.

• He put   a mouse in a closed bell jar with a lighted candle. After that the mouse died due to  suffocation and the candle lost its light.

• Now he put a mint plant  in a bell jar. He observed that  neither candle will extinguish nor will the mouse die.

• He concluded that the carbon dioxide that was produced by animals is responsible for death of mouse and loss of light by candle.

• But with the mint plant, both mouse and candle remain assuming its position .

• He concluded that  mint plants use carbon dioxide and release oxygen.

• This oxygen is necessary for the burning of candles and the lives of mice. Priestley discovered Oxygen gas in 1774.

Julius Von Sachs

• He illustrated that green parts of  plants are capable for the production of carbohydrates like glucose.

• That glucose  is stored in the form of reserve food  as starch. Starch is the first visible product of photosynthesis.

Theodre welhem Engelmann

• He used a prism to split the  light into its component. In second step he placed an illuminated Cladophora placed in a suspension of aerobic bacteria.

• He observed  that bacteria accumulated in blue and red light of the split spectrum.

• He concluded that organisms use different  types of wavelengths of light on photosynthesis.

Cornelius Van Neil 

• He stated that photosynthesis is a light dependent reaction . He  postulated that Hydrogen reduces carbon dioxide for the production of Glucose. 

• In greenplants water is hydrogen donor and release oxygen during photosynthesis . When he used hydrogen sulphide 

• In green sulphur bacteria, instead of water  as hydrogen donor no Oxygen was evolved. 

• He concluded  that oxygen  evolved by green plants comes from water  but not from carbon di oxide.