Photosynthesis usually refers to the process that green plants (including algae) absorb light energy, synthesize carbon dioxide and water into high-energy organic matter, and release oxygen at the same time. It mainly includes two stages: light reaction and dark reaction, involving light absorption, electron transfer, photosynthetic phosphorylation, carbon assimilation and other important reaction steps, which is of great significance to realize natural energy conversion and maintain the balance of carbon and oxygen in the atmosphere.
Humans only know about photosynthesis for about 300 years, but plants evolved this function as early as 3 billion years ago. Scientists came to this conclusion by observing the structure of primitive algae in limestone in southern rhodesia. Then, after living in water for 2.6 billion years and living on land for 400 million years, modern organisms evolved in the photosynthetic system.
More than two thousand years ago, influenced by Aristotle, a famous ancient Greek philosopher, people thought that plants were made of "soil juice", that is, the substances needed for plant growth and development came entirely from soil.
However, in 1648, Belgian doctor Helmont got unexpected results by planting willow. He weighed the willows and the soil and planted them. Five years later, he found that the willow increased by 75 kilograms, but the soil only decreased by 57 grams. Helmont thought that the growth substance of willow came from the water he used to water the trees, but he neglected that the growth of plants needed air and sunlight. However, this is the first great attempt of quantitative experiment in plant nutrition research.
It was not until 1727 that the British botanist Stephen hales put forward the view that air should be used as nutrition for plant growth. Joseph priestley, a famous British chemist, proved by experiments that green plants absorb nutrients from the air.
177 1 year, priestley, England, discovered that plants can restore the air that has become "bad" due to the burning of candles. He did a famous experiment. He put the lighted candle and a mouse in a closed glass cover. The candle went out soon, and the mouse died soon. Then, he put a pot of plants and a lighted candle in a closed glass cover. He found that plants can live for a long time and candles will not go out. Similarly, plants and mice can live normally in a closed glass cover. Finally, he came to the conclusion that plants can renew the burning of candles and pollute the air that animals breathe. But he didn't find the importance of light. Because his outstanding contribution and experimental completion were 177 1 year, this year was designated as the year when photosynthesis was discovered.
However, it is not always successful to repeat his experiment. Until 1779, Dutch plant physiologist Ingenhaus found that plants can "purify" the air only by providing them with enough light. In addition, he also found that plants can not only purify the air in the dark, but also make good air worse like animals. These experiments laid a foundation for human understanding of photosynthesis.
1782, J.Senebier of Switzerland pointed out through chemical analysis that the activity of plants to purify air depends on fixed air (which was later known as carbon dioxide) besides light, but due to the level of chemical development at that time, people did not know what gas plants released in the dark.
It was not until 1785 that people made clear the composition of air that they clearly realized that photosynthesis of plants released oxygen, while carbon dioxide was released during respiration. At this time, human beings have a deeper understanding of photosynthesis.
In the next two hundred years, countless scientists continued to study photosynthesis in depth and achieved many results.
1804, Swiss N.T. de Saussure proved through quantitative experiments that the total amount of organic matter produced and released by plants was greater than that consumed by CO2, which further proved that photosynthesis and water participated in the reaction.
1864, J. V. Sachs found that leaves exposed to iodine would turn blue, which proved that photosynthesis formed carbohydrates (starch).
At the end of 19, it was proved that the raw materials of photosynthesis were CO2 in the air and H2O in the soil, the energy was solar radiation, and the products were sugar and O2.
At the beginning of the 20th century, the molecular mechanism of photosynthesis made a breakthrough. The milestone work is that Wilstadt et al. (19 15) won the Nobel Prize for purifying chlorophyll and clarifying its chemical structure.
From the end of 1940s to 1950s, M. Calvin studied the assimilation of photosynthetic carbon with 14C, and expounded the biochemical pathway of CO2 conversion to organic matter. M Calvin1961won the nobel prize. Subsequently, CAM pathway (M. Thomas, 1960) and C4 pathway (M. D. Hatch and C. B. Slack, 1966) were determined successively.
1965, R.B. Woodward won the Nobel Prize for his work on the total synthesis of chlorophyll molecules.
1At the end of 1980s, Deisenhofer et al. determined the structure of the reaction center of photosynthetic bacteria, and made outstanding progress in understanding the details of membrane protein complex and the study of photosynthetic primary reaction, and won the Nobel Prize of 1988.
1992, Marcus won the nobel prize for his research on the theory of electron transfer in life systems, including electron transfer in photosynthesis.
1At the end of 1990s, great progress has been made in the study of the dynamic structure and reaction mechanism of enzymes that catalyze photosynthetic phosphorylation and respiratory oxidative phosphorylation. Walker and Boyer won the Nobel Prize in 1997.
In addition, it is worth mentioning that three photosynthetic systems have been found in nature: C3, C4 and CAM plants.
Organisms have acquired this magical ability through billions of years of evolution, converting solar energy into chemical energy and storing it in the formed organic compounds. Every year, the solar energy assimilated by photosynthesis is about 10 times the energy needed by human beings. The chemical energy stored in organic matter is not only used by plants themselves and all heterotrophs, but also the energy source for human nutrition and activities. It is believed that with the deepening of research, there will be more important discoveries, which will push human's ability to use energy to a new height.