Note: The oxygen released by photosynthesis comes from water, and the products of photosynthesis are not only sugar, but also amino acids (excluding protein) and fats, so the products of photosynthesis should be organic.
Each step of the reaction:
H2O→H+O2 (photolysis of water)
NADP++2e-+H+ → NADPH (hydrogen transfer)
ADP→ATP (energy transfer)
CO2+C5 compound →C3 compound (fixed carbon dioxide)
C3 compound →(CH2O)+ C5 compound (formation of organic matter)
The process of photosynthesis: 1 The chemical reaction in the first stage of photosynthesis must have light energy, which is called photoreaction stage. The chemical reaction in the photoreaction stage is carried out on the thylakoids of chloroplasts. The chemical reaction in the second stage of photosynthesis in the dark reaction stage can be carried out without light energy. This stage is called dark reaction stage. The chemical reaction in the dark reaction stage is carried out in the matrix in chloroplast. The light reaction stage and dark reaction stage are a whole, which are closely related and indispensable in the process of photosynthesis.
Photosynthesis refers to the process that green plants use light energy through chloroplasts to convert carbon dioxide and water into organic substances that store energy and release oxygen. We breathe in oxygen released by photosynthesis all the time. The food we eat every day also comes directly or indirectly from organic matter produced by photosynthesis. So, how was photosynthesis discovered?
Until photosynthesis was discovered in the middle of18th century, people always thought that all the nutrients in plants were obtained from the soil, but they didn't think that plants could get anything from the air. 177 1 year, British scientist priestley found that it is not easy to extinguish the lighted candle in a closed glass cover with green plants. When mice are placed in a glass cover with green plants, they are not easy to suffocate. Therefore, he pointed out that plants can renew the air. But he didn't know which pattern plants were updated in the air, and he didn't find the key role of light in this process. Later, after many scientists' experiments, the places, conditions, raw materials and products of photosynthesis were gradually discovered. Here are some famous experiments. 1864, a german scientist saxophone made an experiment: put the green leaves in the dark for several hours in order to consume the nutrients in the leaves. Then expose half of the blade and cover the other half. After a period of time, the leaves were treated with iodine vapor, and it was found that half the color of the dark side of the leaves remained unchanged, while the exposed half was dark blue. This experiment successfully proved that green leaves produce starch in photosynthesis.
1880, German scientist engelmann conducted an experiment on the photosynthesis of Spirogyra: put a temporary package containing aerobic bacteria in a dark environment without air, and then irradiate Spirogyra with a very thin beam. Through microscopic observation, it was found that aerobic bacteria only concentrated near the position where chloroplasts were irradiated by light beams. If the temporary package is completely exposed to light, aerobic bacteria will concentrate around all the light-receiving parts of chloroplasts. Engelmann's experiment proves that oxygen is released from chloroplast, which is the place where green plants carry out photosynthesis.
The process of photosynthesis:
The chemical reaction in the first stage of photosynthesis in the photoreaction stage can only be carried out with light energy. This stage is called photoreaction stage. The chemical reaction in the photoreaction stage is carried out on the thylakoids of chloroplasts.
The chemical reaction in the second stage of photosynthesis in the dark reaction stage can be carried out without light energy. This stage is called dark reaction stage. The chemical reaction in the dark reaction stage is carried out in the matrix in chloroplast. The light reaction stage and dark reaction stage are a whole, which are closely related and indispensable in the process of photosynthesis.
The Significance of Photosynthesis Photosynthesis provides material and energy sources for the survival of almost all living things, including human beings. Therefore, photosynthesis is of great significance to human beings and even the whole biological world. The significance of photosynthesis can be summarized as the following aspects;
First, make organic matter. The amount of organic matter produced by green plants through photosynthesis is huge. It is estimated that the green plants on the earth produce about 450 billion tons of organic matter every year, far exceeding the total output of industrial products on the earth every year. Therefore, people compare the green plants on the earth to a huge "green factory". The survival of green plants is inseparable from the organic matter produced by photosynthesis. Food for humans and animals also comes directly or indirectly from organic matter produced by photosynthesis.
Second, convert and store solar energy. Green plants convert solar energy into chemical energy through photosynthesis and store it in organic matter produced by photosynthesis. Almost all living things on the earth use this energy directly or indirectly as the energy of life activities. In the final analysis, the energy contained in fuels such as coal, oil and natural gas was stored by ancient green plants through photosynthesis.
Third, make the contents of oxygen and carbon dioxide in the atmosphere relatively stable. It is estimated that all living things in the world consume an average of 10000 t/s (ton/s) by breathing and burning various fuels. At this rate of oxygen consumption, the oxygen in the atmosphere will be exhausted in about two thousand years. However, this did not happen. This is because green plants are widely distributed on the earth, constantly absorbing carbon dioxide and releasing oxygen through photosynthesis, so that the contents of oxygen and carbon dioxide in the atmosphere remain relatively stable.
Fourthly, it plays an important role in biological evolution. Before the appearance of green plants, there was no oxygen in the earth's atmosphere. Only 2 billion to 3 billion years ago, green plants appeared on the earth and gradually took advantage, and the earth's atmosphere gradually contained oxygen, thus enabling other creatures on the earth to have aerobic respiration. Because part of the oxygen in the atmosphere is converted into ozone (O3). The ozone layer formed by ozone in the upper atmosphere can effectively filter out the ultraviolet rays that have a strong destructive effect on organisms in solar radiation, so that aquatic organisms can gradually live on land. After a long process of biological evolution, a variety of animals and plants widely distributed in nature finally appeared.
Relationship between Spectrum and Plant Photosynthesis
In recent years, the influence of light quality on plant growth and morphology has attracted researchers' attention. For example, Japanese academic circles focus on the influence of LED monochromatic light on the growth characteristics of tissue culture seedlings. In Israel, plastic plates with different colors are used as coating materials to explore the effects on the growth of leafy vegetables and foliage plants.
The most famous literature about the relationship between light quality and plant development is "Photomorphogenesis in Plants" written by R. E. Kendrick and G. H. M. Kronenberg (1986, Martinus Nijhoff Press). The information is as follows:
Effects of Spectral Range on Plant Physiology
280 ~ 3 15nm has little effect on morphological and physiological processes.
3 15 ~ 400nm chlorophyll absorption is less, which affects the photoperiod effect and hinders stem elongation.
The absorption rate of chlorophyll and carotenoids is the largest at 400 ~ 520nm (blue), which has the greatest influence on photosynthesis.
The absorption rate of 520 ~ 6 10nm pigment is not high.
6 10 ~ 720nm (red) chlorophyll absorption rate is low, which has a significant impact on photosynthesis and photoperiod effect.
The absorption rate at 720 ~ 1000nm is low, which stimulates cell elongation and affects flowering and seed germination.
> > 1000nm heating.
In the July (2) issue of Flower Technology, 2004, there was an article discussing the influence of light color on photosynthesis. The author is Mr Harry Steagall. The article subtitle indicates that it is generally believed that the color of light has different effects on photosynthesis. In fact, there is no difference in the effect of light and color in the process of photosynthesis, so the use of full spectrum is most beneficial to the development of plants.
The sensitivity of plants to spectrum is different from that of human eyes. The most sensitive spectrum of human eyes is 555nm, which is between yellow light and green light. It is not sensitive to blue light and red light. However, plants are the most sensitive to red light spectrum, but not sensitive to green light, but the difference in sensitivity is not as great as that of human eyes. The most sensitive area of plants is 400 ~ 700 nm. This spectrum is usually called the effective energy region of photosynthesis. About 45% of sunlight energy exists in this spectrum. Therefore, if the artificial light source is used to supplement the light quantity, the spectral distribution of the light source should also be close to this range.
The photon energy emitted by the light source varies with the wavelength. For example, the energy with a wavelength of 400 nm (blue light) is 1.75 times that of 700 nm (red light). But for photosynthesis, the two wavelengths have the same effect. Excess energy in the blue spectrum that cannot be used for photosynthesis is converted into heat. In other words, the photosynthetic rate of plants is determined by the number of photons that plants can absorb in the range of 400~700nm, regardless of the number of photons emitted by each spectrum. However, it is generally believed that the color of light affects the rate of photosynthesis. Plants have different sensitivities to all spectra. This reason comes from the special absorption of pigment by leaves. Among them, chlorophyll is the best known. But chlorophyll is not the only useful pigment in photosynthesis. Other pigments also participate in photosynthesis, so photosynthetic efficiency can not only consider the absorption spectrum of chlorophyll.
The difference of photosynthesis path is also independent of color. Light energy is absorbed by chlorophyll and carotene in leaves. Energy is converted into glucose and oxygen by fixing water and carbon dioxide through two photosynthetic systems. This process uses the spectrum of all visible light, so the influence of light sources of various colors on photosynthesis is almost the same.
Some researchers believe that the photosynthetic capacity of orange light is the largest. But this does not mean that plants should be cultivated under this monochromatic light source. For the morphological development and leaf color of plants, plants should receive various balanced light sources.
Blue light (400~500nm) is very important for plant differentiation and stomatal regulation. If the blue light is insufficient and the far red light is too much, the stem will grow excessively, which will easily cause the leaves to turn yellow. When the ratio of red spectrum (655~665nm) energy to far red spectrum (725~735nm) energy is between 1.0 and 1.2, the plant development will be positive. But each plant has different sensitivity to these spectral ratios.
High-pressure sodium lamps are often used as artificial light sources in greenhouses. Take Philips Master SON-TPIA as an example, it has the highest energy in the orange spectral region. The energy of far infrared light is not high, so the energy ratio of red light to far red light is greater than 2.0. However, because there is still natural sunlight in the greenhouse, the plants have not become short. If this light source is used in a growth box, it may have an impact. )
In natural sunlight, blue light energy accounts for 20%. For artificial light sources, such a high proportion is not needed. For normal plants, most plants only need 6% blue light energy in the range of 400~700nm. In natural sunlight, there is enough blue light energy. Therefore, the artificial light source does not need to supplement more blue light spectrum. However, when the natural light source is insufficient (such as winter), the artificial light source needs to increase the blue light energy, otherwise the blue light source will become a limiting factor for plant growth. However, if the light source improvement method is not adopted, there are still other methods to remedy the problem of insufficient light source. Such as temperature regulation or administration of growth hormone.
(Postscript):
The research results of BSE laboratory on the relationship between light source and the development of plant tissue culture seedlings have two conclusions similar to this paper:
1. The color of the light source does not affect the rate of photosynthesis, so it does not affect the fresh weight or dry weight. The main factors affecting the rate of photosynthesis are still light quantity and temperature.
Second, the light quality affects the morphology of tissue culture seedlings, such as the pitch length (seedling height), chlorophyll content in leaves, and the ratio of underground objects to underground objects. (Chen Jiazhong, biosystems engineering Research Office, Zhongxing University)
References:
Window of Science and Technology/Yunnan Horticultural Exposition on Flowers, Landscaping and Vegetables
photosynthesis
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Photosynthesis is a biochemical process in which plants, algae and some bacteria use chlorophyll to convert carbon dioxide and water into glucose and release oxygen under the irradiation of visible light. Plants are called producers of food chain because they can use inorganic substances to produce organic substances and store energy through photosynthesis. By eating, consumers in the food chain can absorb the energy stored by plants, with an efficiency of about 30%. For almost all creatures in the biological world, this process is the key to their survival. Photosynthesis is the most important part of the earth's carbon and oxygen cycle.
Directory [hidden]
1 Discovery of photosynthesis
Principle 2
2. 1 bright reaction and dark reaction
2. 1. 1 photoreaction
2. 1.2 dark reaction
2. 1.2. 1 C3 plants
2. 1.2. 1. 1 calvin cycle
2. 1.2.2 C4 factory
2. 1.2.2. 1 See.
2. 1.2.3 Sedum acid metabolizing plants
Photosynthesis of algae and bacteria
4 Research significance
5 links
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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.
177 1 year, priestley, England, discovered that plants can restore the air that has become "bad" due to the burning of candles.
1773, Innhaus of the Netherlands proved that only the green parts of plants can make the air "better" under light.
From 65438 to 0804, Saussure of Switzerland further confirmed that carbon dioxide and water are raw materials for plant growth through quantitative research.
1845, Meyer in Germany discovered that plants convert solar energy into chemical energy.
1864, saxophone in Germany discovered that photosynthesis produces starch.
1880, chloroplasts were found to be places of photosynthesis in engelmann, USA.
1897, which is called photosynthesis for the first time in textbooks.
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principle
Unlike animals, plants have no digestive system and must rely on other ways to absorb nutrients. Is the so-called autotroph. For green plants, in sunny days, they will use the energy of sunlight to carry out photosynthesis and obtain nutrients necessary for growth and development.
The key participant in this process is the internal chloroplast. Under the action of sunlight, chloroplasts convert carbon dioxide entering leaves through stomata and water absorbed by roots into glucose and release oxygen at the same time;
12H2O+6 CO2+ light → C6H 12O6 (glucose)+6o2 =+6o2.
note:
1 The water on both sides of the equal number in the above formula cannot be offset, although the formula is very special in chemistry. The reason is that the water on the left is absorbed by plants to make oxygen and provide electrons and hydrogen ions. The oxygen atom of the water molecule on the right comes from carbon dioxide. In order to express the initial process of this raw material product more clearly, people are more accustomed to writing water molecules on the left and right sides of the equal sign, or putting an asterisk on the upper right corner of water molecules.
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Bright reaction and dark reaction
Photosynthesis can be divided into two steps: light reaction and dark reaction.
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Photoinduced reaction
Background: Chloroplast membrane
Influencing factors: light intensity, water supply
Two absorption peaks of plant photosynthesis
The absorption peak process of chlorophyll a and chlorophyll b: two sets of photosynthetic systems on chloroplast membrane: photosynthetic system I and photosynthetic system II. (Photosynthetic system I is more primitive than photosynthetic system II, but electron transfer begins first. Under illumination, photons with wavelengths of 680nm and 700nm are absorbed, and as energy, electrons obtained from the photolysis path of water molecules are continuously transferred, and finally transferred to coenzyme NADP. However, due to different concentrations, hydrogen ions obtained by water photolysis move from thylakoid to matrix through the protein complex on thylakoid membrane, and the potential energy between them decreases, which is used to synthesize ATP for dark reaction. At this time, the hydrogen ions with reduced potential energy are taken away by the hydrogen carrier NADP. One NADP molecule can carry two hydrogen ions. This NADPH+H ion acts as a reducing agent in the dark reaction.
Significance: 1: photolyses water to produce oxygen. 2. Convert light energy into chemical energy, generate ATP, and provide energy for dark reaction. 3.NADPH+H ion is synthesized from hydrogen ion, which is the product of water photolysis, and provides reducing agent for dark reaction.
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Carbon fixation/photo-independence/carbon assimilation
The essence is a series of enzymatic reactions.
Environment: chloroplast matrix
Influencing factors: temperature, carbon dioxide concentration
Process: Different plants have different dark reaction processes, and the anatomical structure of leaves is also different. This is the result of plants adapting to the environment. Dark reactions can be divided into three types: C3, C4 and cam. These three types are divided according to the different processes of carbon dioxide fixation.
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C3 factory
After World War II, malvin Calvin of the University of California, Beckley and his colleagues studied an algae called Chlorella to determine how plants fix carbon dioxide in photosynthesis. At this time, C 14 tracer technology and two-way paper chromatography technology have matured, and Calvin just used these two technologies in the experiment.
They put the cultured algae into a closed container filled with unlabeled CO2, and then injected CO2 labeled with C 14 into the container. After a short period of culture, they immersed the algae in hot ethanol to kill the cells, so that the enzyme denaturation in the cells failed. Then they extract molecules from the solution. Then the extract was separated by two-way paper chromatography, and radioactive spots were analyzed by autoradiography, and compared with known chemical components.
Calvin found in the experiment that CO2 labeled with C 14 can be quickly transformed into organic matter. Within a few seconds, radioactive spots appeared on the chromatographic paper. Compared with other chemicals, the chemical component in the spots is 3- phosphoglyceric acid (PGA), which is an intermediate product of glycolysis. The product of this first extraction is a three-carbon molecule, so this CO2 fixation pathway is called C3 pathway, and plants that fix CO2 through this pathway are called C3 plants. Later studies also found that CO2 fixation through C3 pathway is a cyclic process, which is called C3 cycle. This cycle is also called calvin cycle.
For C3 plants, such as rice and wheat, carbon dioxide directly enters mesophyll through stomata, that is, leaves for calvin cycle. However, the vascular bundle sheath cells of C3 plants are very small and contain no or a small amount of chloroplasts, so calvin cycle does not occur here.
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calvin cycle
Calvin cycle is part of the dark reaction of photosynthesis. The reaction site is the matrix in chloroplast. The cycle can be divided into three stages: carboxylation, reduction and rubp regeneration. Most plants will absorb a molecule of carbon dioxide and integrate it into the second carbon atom of pentose molecule 1, 5-RuBP (rubp) through the action of an enzyme called rubp carboxylase. This process is called carbon dioxide fixation. The significance of this reaction is to activate the originally inactive carbon dioxide molecules for later reduction. However, this hexacarbon compound is extremely unstable and will be immediately decomposed into two molecules of three-carbon compound 3- phosphoglyceric acid. The latter is reduced by NADPH+H produced in photoreaction, which needs to consume ATP. The product is triose 3- phosphate. Later, after a series of complex biochemical reactions, glucose will be synthesized with one carbon atom and leave the cycle. The remaining five carbon atoms undergo some column changes, and finally a 1, 5-rubp is generated, and the cycle begins again. Circulate for six times to generate one molecule of glucose.
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C4 factory
In 1960s, Australian scientists Hatch and slack discovered that tropical green plants such as corn and sugarcane existed in calvin cycle as other green plants, and CO2 was first fixed in a special way. This route is also called hatch slack route.
C4 plants mainly live in arid and tropical areas. In this environment, if plants open their stomata for a long time to absorb carbon dioxide, it will lead to the rapid loss of water through transpiration. Therefore, plants can only open their stomata in a short time, and the intake of carbon dioxide is bound to be less. Plants must use this small amount of carbon dioxide for photosynthesis and synthesize substances needed for their own growth.
There is a vascular bundle sheath around the vascular bundle of C4 plants, which is composed of chloroplasts, but there is no grana or abnormal development. Here, mainly calvin cycle.
Its mesophyll cells contain a unique enzyme, namely phosphoenolpyruvate carbon oxidase, which makes carbon dioxide assimilated by a three-carbon compound-phosphoenolpyruvate to form a four-carbon compound oxaloacetic acid, which is also the origin of this dark reaction type name. After this oxaloacetic acid is converted into malic acid, it enters the vascular bundle sheath, which will decompose and release carbon dioxide and a molecule of pyruvate. After carbon dioxide enters calvin cycle, it goes through C3 process. Pyruvate will synthesize phosphoenolpyruvate again, consuming ATP.
The advantage of this type is that the carbon dioxide fixation efficiency is much higher than that of C3, which is beneficial to the growth of plants in arid environment. Starch obtained by photosynthesis of C3 plants will be stored in mesophyll cells, because this is the site of calvin cycle, and vascular bundle sheath cells do not contain chloroplasts. The starch of C4 plants will be stored in vascular bundle sheath cells, because the calvin cycle of C4 plants occurs here.
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For more information, see.
C4 factory
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Sedum acid metabolizing plant
Sedum acid metabolism (CAM): If C4 plants stagger the fixation of carbon dioxide and calvin cycle in space, then the cycle of Sedum acid is also staggered in time. Plants that use this method are those with swollen fleshy leaves, such as pineapples. These plants open their stomata at night, absorb carbon dioxide, and fix carbon dioxide through incubation-relaxation. Close the pores in the morning to avoid excessive water loss. At the same time, mesophyll cells begin Kelvin cycle. These plants also have high carbon dioxide fixation efficiency.
For details, please see: Sedum acid metabolizing plants.
Significance: The immobilization of carbon dioxide increases the chemical activity of chemically inactive carbon dioxide, which is reduced and finally synthesized into glucose.
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Photosynthesis of algae and bacteria
Eukaryotic algae, such as red algae, green algae and brown algae, have chloroplasts like plants and can also produce oxygen for photosynthesis. Light is absorbed by chlorophyll, and many algae have other different pigments in their chloroplasts, giving them different colors.
Photosynthetic bacteria have no chloroplasts, but are directly carried out by the cells themselves. Cyanobacteria (or "cyanobacteria") belonging to prokaryotes also contain chlorophyll, which produces oxygen and photosynthesis like chloroplasts. In fact, it is generally believed that chloroplasts evolved from cyanobacteria. Other photosynthetic bacteria have a variety of pigments, called bacterial chlorophyll or bacteriocin, but do not oxidize water to produce oxygen, and use other substances (such as hydrogen sulfide, sulfur or hydrogen) as electron donors. Non-oxygen-producing photosynthetic bacteria include purple sulfur bacteria, purple non-sulfur bacteria, green sulfur bacteria, green non-sulfur bacteria and solar bacteria.
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Research significance
The study of photosynthesis plays a fundamental guiding role in agricultural production, environmental protection and other fields. Understanding the influencing factors of light reaction and dark reaction can benefit and avoid disadvantages, such as building greenhouses and speeding up air circulation, thus increasing crop yield. It is known that rubp carboxylase has two sides, that is, it not only catalyzes photosynthesis, but also promotes photorespiration. They tried to transform it to reduce the latter, avoid consuming organic matter and energy, and increase crop yield.
When we understand the relationship between photosynthesis and plant respiration, people can better decorate their family plants. For example, don't put plants indoors at night to avoid the reduction of indoor oxygen concentration caused by plant respiration.
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interconnection
/wljc/xbs wx/8/experiment/experiment _ 08 . htm
Simple comparison of three kinds of plants
From "blog.org/wiki/%E5% 85% 89% E5% 90% 88% E4% BD% 9c% E7% 94% A8.
Because photosynthesis is mainly carried out in chloroplasts, and chlorophyll in chloroplasts is the main pigment involved in photosynthesis. There is magnesium ion in chlorophyll, and its * * * is composed of porphyrin ring.
Of course, photosynthesis is a series of processes, and the buffering conditions in cells, the auxiliary groups of enzymes and so on all need the participation of mineral elements.
So it can be said that photosynthesis is influenced by mineral elements.
The answer is that both D light reaction and dark reaction need enzymes.
Chlorophyll can leave mesophyll for photosynthesis.
B the temperature is too low, the enzyme is inactivated and photosynthesis cannot be carried out.
CADP-ATP is the product of dark reaction, not light reaction.