The discovery of photosynthesis
Aristotle, an ancient Greek philosopher, believed that all substances needed for plant growth came from soil. Van Ermont, a Dutchman, made a weighing experiment of potted willow, and concluded that the weight of plants mainly comes from water rather than soil. He didn't realize that substances in the air participated in the formation of organic matter. At about this time, Song of China in the late Ming Dynasty said in his book On Qi: "Qi is pushing a grain from the ground, the small one is a canopy, and the big one is a tree with a cow. What is the original geometric shape of this grain? The rest are gasified. " Clearly realize that substances in plants (and animals) are transformed from qi. 177 1 year, J. priestley found that plants can restore the air that has become "bad" because of candle burning. 1773, J. Innhaus of the Netherlands proved that only the green parts of plants can make the air "better" under light. 1804 Swiss N.-T. de Saussure further confirmed that CO2 and water are raw materials for plant growth through quantitative research. 1845, J.R. Meyer of Germany discovered that plants convert solar energy into chemical energy. 1860, people have used CO2+H2O→(CH2O)+O2.
Represents the whole process of plants using light energy. 1897 is called photosynthesis for the first time in textbooks.
In the 1930s, C.B. Vannell discovered that some bacteria could use light energy to perform photosynthesis-like reactions under anaerobic conditions. However, they obtain hydrogen for reducing carbon dioxide from hydrogen sulfide and the like. Instead of water, and does not release oxygen. He called this reaction bacterial photosynthesis. In addition, it is also found that some bacteria can obtain energy by oxidizing some inorganic substances for organic synthesis, which is similar to photosynthesis and called chemical synthesis.
The discovery of photorespiration
Humans have long noticed that the flowering time of many plants is relatively stable, but the role of photoperiod in determining flowering time was not understood until the 20th century. 19 12 cannabis was discovered in tournois, France. It will bloom under the condition of 6 hours short sunshine every day, and stay in the vegetative growth stage under the condition of long sunshine. 19 13 german G.A. Krebs found that artificially extending the daily sunshine time can make Sem-pervivum plants that usually bloom in June bloom in winter. But it was American horticulturists W.W. Ghana and H.A. Allard who clearly put forward the photoperiod theory. In 1920, they found that when tobacco is a variety. The Maryland mammoth, which usually blooms in the southern United States, was moved to the northern United States for cultivation. It only grows leaves and does not bloom in summer. But if you move into a greenhouse in autumn and winter, you can blossom and bear fruit. In the northern summer, shading can shorten the sunshine hours to less than 14 hours per day, and also make them bloom. Later, soybean (Biloch West variety), perilla and sorghum were discovered. There is also this phenomenon, and each has its own upper limit of the length of the day. When the sunshine length is less than this value, it can blossom, which is called the critical day length. At the same time, it is found that spinach, radish and other plants, on the other hand, can bloom only when the sunshine length exceeds a critical day length.
The discovery of cells
Most of the cells that make up animals and plants are only 20-30 microns, while the resolution of human eyes is only 100 micron. So before the invention of the microscope, it was impossible for people to know what cells were. Galileo, a famous Italian scientist, observed some small animals with his own simple microscope in 16 10. Later, Levin Hooke, a Dutch cloth dealer, grinded a short-focus lens and made a simple microscope to observe the water droplets in the pond. Many tiny creatures were found in the water, but these microscopes were very simple and could not see the tiny nodules in the organisms.
1665, the British scientist Hooke observed some thin cork cut with a sharp knife with his own microscope. He saw that wood chips were made up of many small honeycomb grids. He called these small rooms "cells". At that time, he thought that these chambers played a role similar to blood vessels in animals, and liquid flowed in them to transport nutrients in life. In fact, all he saw at that time was the cell wall of a dead plant cell. However, Hooke's description of microscopic animal cells is the first observation record of human cells.
The door to the cellular world has been opened. However, because the microscopes used at that time were all hand-grinded, there were many chemicals, which were expensive and of poor quality, there was little progress in the knowledge about cells in the nearly 50 years from 1675- 1830.
Establishment of cell theory
Cell theory holds that organisms are composed of cells, which are the basic structure, functional unit and development basis of organisms. After hundreds of years of research, the formation of cell theory has been gradually perfected. At the end of 16 and the beginning of 17, the microscope provided an effective means to explore the biological microstructure. /kloc-in the middle of the 0 th/7 th century, an Englishman Hooke first observed plant cells. At the same time, Levin Hooke of the Netherlands and Marby Ji of Italy also saw plant cells one after another. However, it is not recognized that cells are independent living structural units in the plant kingdom. /kloc-At the beginning of the 9th century, German botanists Treviranus and Moore clarified that cells are the structural units of plants and called their contents protoplasm.
By the early 1930s of 19, Brown observed that most plant cells had nuclei. Pujin Ye also observed chicken embryos. Moore and negri put forward that the protoplasm of plant and animal cells is basically the same, so far, the basic concept of cell has been established. 1838, German botanist Schleiden put forward the cell theory of plant structure in his Theory of Phytogenesis. He believes that the cell is the basic unit of all plant structures and the entity of all plant development. The simplest plant is composed of one cell, and most plants are composed of multiple cells; The formation of plant cells is that a new cell originates from the nucleus of an old cell, initially forming a lobe of the old cell sphere, and then separating itself into a complete cell.
1839 Wang Shi, a German anatomy professor, extended Schleiden's viewpoint to the animal kingdom. He put forward the theory that animals and plants are made up of cells in his paper "Microscopic study on the consistency of animal and plant structure and growth". He believes that no matter how different the basic parts of an organism are, there is always a universal principle of development, and this principle is cell formation.
Schleiden and Wang Shi laid the foundation of cell theory. The cell theory was later supplemented and revised by many biologists, and it became more and more perfect. The general contents are as follows: all living things are composed of cells and their products, all cells are similar in structure and composition, each performs a specific function, and can survive independently, with the same life process; Organisms reflect their functions through the activities of their cells; New cells are divided into existing cells; Because it is binary, all kinds of cells have their own process of occurrence and development; Biological diseases are caused by abnormal cell metabolism and metabolism.