• Renu Joshi, Ph. D.

Photosynthesis - The Backbone of Ecosystem



Chlorophyll is this part that absorbs sunlight and also uses its ability to synthesize carbohydrates from environmental carbon dioxide and water by the process called photosynthesis and is the foundation for sustaining the life processes of plants. Since animals and people acquire their food source by having several plants (or crops) in their food chain, photosynthesis can be regarded as the source of our life too. In 1780, renowned English chemist Joseph Priestley found that plants could restore air that's been burnt by the burning of candles. He placed a mint plant in a glass jar with a candle and observed pattern of candle burning longer or lesser in comparison when the plant wasn’t in the same jar and found that there is a variation. Later a Dutchman, Jan Ingenhousz, a court physician to the empress provided a major contribution to the study of photosynthesis and may be considered as the discoverer of photosynthesis. He roughly conducted around 500 experiments and found that light plays a major role in photosynthesis. His experiments were based on the observations of Priestley. He discovered that plants not only possess the ability to improve atmospheric quality but also an effect of light on plants positively impacts their growth.


Soon enough, more pieces of this puzzle were revealed by two chemists working in Geneva. Jean Senebier, a Swiss pastor, revealed that fixed air was taken up during photosynthesis, and also Theodore de Saussure found the other reagent needed was water.


Chemical Process

The actual chemical equation that takes place is the reaction between CO2 and water, powered by sunlight, to produce glucose and also another product, oxygen. The glucose sugar is either directly utilized as an ability source by the plant for metabolic process or growth, or is polymerized into form starch, so it may be stored until needed. The waste oxygen is expelled into the atmosphere. The carbohydrates generated (may or may not be glucose) are the food necessary for plants. This reaction is light dependent i.e. requires sunlight to happen.


The bi-products (ATP and NADPH) of light-dependent activity are fed into light independent activities those happen in absence of sunlight. It is worthwhile to add that the CAM (Crassulacean acid metabolism) photosynthesis stomata open in the night to collect CO2. This process is comparatively complex but must be considered as an additional information source to understand full photosynthesis process.


Renu Joshi, Ph. D.

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