plants

         Photosynthesis

    Photosynthesis converts massive amount of Sunlight into electrical and then chemical energy. The input is carbon dioxide (CO2), water (H2O), minerals and light, and the output is carbohydrates (food) that we need for our nourishment, and oxygen that we need to breathe [Ref. 1] This oxygenic photosynthesis occurs in higher plants (e.g., rice, maize, wheat, mosses, ferns, forest trees, shrubs, etc); in green, red, brown and yellow algae, and even blue-green cyanobacteria. There are photosynthetic bacteria (e.g., purple and green bacteria; and heliobacteria) that can produce carbohydrate (food), but no oxygen. They are called anoxygenic photosynthesizers. Instead of the all-abundant water, they use H2S or even organic matter. Oxygenic photosynthesizers use the green pigment Chlorophyll a, located in protein complexes in photosynthetic membranes, to run the photochemistry of the process, whereas the anoxygenic photosynthesizers use Bacteriochlorophyll instead. The set of photosynthetic reactions are arbitrarily divided into (1) the light phase (that produces the reducing power and ATP, the energy currency of life); and (2) the dark phase (where the products of light phase are used to convert CO2 to carbohydrates).

Photosynthesis is the most important biological process on Earth. It serves as the World's largest solar battery. The primary reactions have close to 100% quantum efficiency (i.e., one quantum of light leads toone electron transfer); and under most ideal conditions, the overall energy efficiency can reach 35%. Due to losses at all steps in biochemistry, one has been able to get only about 1 to 2% energy efficiency in most crop plants. Sugarcane is an exception as it can have almost 8% efficiency. However, many plants in Nature often have only 0.1 % energy efficiency. Due to massive vegetation, the total productivity is very high indeed. (Deforestation is a bad deal for all of us because it would add to the already increasing CO2 in the atmosphere and its attendant consequences, such as global warming.) The photosynthesis of the past is what had stored the Sun's energy that ultimately produced coal; natural gas; and the petroleum (called petrol in India and gas in USA). Photosynthesis also provides us with the fiber, the clothing, and indirectly all the building materials including our Macs and PCs. In the villages in India, firewood, used for cooking and heating, also owes its existence to Photosynthesis. We cannot leave out the dried "cowdung" (gobar) from the scene. The cow that produced it clearly ate hay that was the dried form of what photosynthesis had produced for her. Thus, we depend upon the process for our existence in more ways than is often considered. Perhaps, the Earth is the only hospitable planet for our lives. In short, our Sun God (Suraj Devta) has given us this life through Photosynthesis.

The major problem is that increasing population pressures may cause havoc in our Society if the future Photosynthesis cannot support it. Thus, it is essential to understand the intricacies of the process and exploit it to our benefit. We need to learn how to improve crop productivity; how to go after sustainable agriculture; and how to invent means such that plant biotechnology becomes our friend, not our enemy; and how to mold plants by genetic engineering to provide us with cheap vaccines and medicines. Finally, the impact of global climate change on Photosynthesis and of Photosynthesis on global climate change needs to be understood [Refs. 2 and 3]. Thus, it is necessary to train scientists who will exploit the molecular and cellular aspects of photosynthesis, and also those who will go after integrating the information at a systems level. Both must go on hand in hand in order for the future to be bright for our grand children and great grand children.

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Photosynthesis is a process of plant feeding.