Julius Robert Mayer (1814-1878). Julius Robert von Mayer was a German physician and physicist. He was the first to state the Law of the Conservation of Energy: energy is neither created nor destroyed. He stated that the sun is the ultimate source of energy for both plants and animals and that when absorbed plants convert this light energy to chemical energy through the process of photosynthesis (Devlin 1975).
Julius Robert Mayer made his claim in his The Organic Motion in its Relation to Metabolism which was published in 1845. In this publication he wrote: "The plants take in one form of power, light; and produce another power: chemical difference." He used the term ‘power’ for energy and ‘chemical difference’ for chemical energy. He therefore made it clear that plants do not only produce organic matter but also provide the energy which sustains life. Consequently, his finding has made further enlightenment on photosynthesis. The process of photosynthesis in plants can now be represented by the following equation (life.illinois.edu n.d.):
CO2 + H2O + light ---- > O2 + organic matter + chemical energy
It is now fully established that the sun is the sole source of energy for almost all life on Earth and that this light energy (electromagnetic energy) is converted to chemical energy within the plant through the process of photosynthesis.
It is estimated that every year photosynthesis stores about 4 x 1018 kilojoules of free energy in organic matter. This necessarily requires the convertion of 1011 metric tons of carbon dioxide into organic matter (Govindjee 2000). This explains why plants, particularly the perennial trees, are important in mitigating global warming which environmentalists mainly attribute to increased concentration of carbon dioxide in the atmosphere. They have the ability to store vast amounts of carbon dioxide, a process called carbon dioxide sequestration (click to read related page).
By comparison, Went and the Editors of Life (1963) also explained the massive scale in which photosynthesis produces chemical energy from light energy. They made the following comparison: “Every year the world’s steel mills turn out 350 million tons of steel, the world’s cement factories 325 million tons of cement. The world’s green plants, however, produce 150 billion tons of sugar every year...”
Julius Robert Mayer would not know of these statistics then, but his discovery has made photosynthesis the single most important physiological process on Earth.
Note: The list of Literature Cited is in the History of Photosynthesis Mainpage.
(Ben G. Bareja, July 2012)
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