What is photorespiration Photorespiration (English: photorespiration) is that all the cells carry out photosynthesis (where "cell" includes prokaryotes and eukaryotes, but not all of these cells can run the full light of breathing) in low light and carbon dioxide under high oxygen occurrence of a biochemical process. It is a loss of photosynthetic energy side effects. Process oxygen is consumed and will produce carbon dioxide. Photorespiration photosynthesis about 30% off. Thus reducing photorespiration is considered one of the ways to improve the performance of photosynthesis. But it was discovered later photorespiration has a very important role in cell protection. In the process of photorespiration, photosynthesis in a pair of combinations: the reactant 1,5 - ribulose bisphosphate (ribulose-1 ,5-bisphosphate, referred to as rubp) and catalyst 1,5 - bisphosphate carboxylase ribulose enzyme / oxygenase (ribulose-1 ,5-bisphosphate carboxylase / oxygenase, referred to as rubisco) had their different reactions in photosynthesis. rubp increase in the role of rubisco two oxygen atoms, then after a series of reactions that ultimately generate 3 - phosphoglycerate. The latter then through part of the photosynthesis process, students can again become rubp. First, the research history Photorespiration and photosynthesis in the atmosphere at the same time light conditions, with cells themselves will carry out respiration, gas exchange methods in general difficult to detect and measure photorespiration. Therefore, the discovery of photorespiration later. In 1920, Germany's Otto Wabu (otto warburg) found that photosynthetic rates because of the increase of oxygen partial pressure decreased, and later was named this phenomenon Wabu effect. And John de Cole (john decker) accidental experiment in 1955, the tobacco leaves were observed after the sudden stop at the light released large amounts of carbon dioxide. He was called the "burst of carbon dioxide," and that this is occurring in the lighting conditions, "breathe." Photorespiration have this name. The early 60s, scientists using infrared co2 analyzer and isotope tracing techniques to better understand the light breathing. 1972, by Edward Talbot (nathan edward tolbert) officially stated photorespiration mechanism. But the enzymes involved in the process after a very long time to get recognition, but it is for the intermediate product in the transport of organelles and the regulation of photorespiration, is poorly understood. II Concept "Light Breathing" contains "breathe" the term, but the process is not a real cell respiration, respiratory cells under light respiration is carried out by real professionals called dark respiration (cellular respiration is the cellular decomposition of organic matter to produce energy process, and daily heard the breathing is different, the latter refers to the respiratory gas exchange. Note: If the text referred to breathe, referring to both cell respiration). With "dark" character is to be different with photorespiration, because photorespiration will occur only in the light, which is the name of "light" (Greek: Φωτο) origin. Both in light and dark respiration, but also occur under the circumstances there is no light. Photorespiration was called "breathing" word (in English: respiration), is because photorespiration and respiration (breathing cell line was light and dark respiration) as input and output, that took part in the reaction of oxygen consumption was , the process releases carbon dioxide. However, in addition to the need for both light differences on this point, there is the process of photorespiration consumes atp, namely energy, but also consumes reducing equivalents nadph, this is not the same and dark respiration and dark respiration of cells get energy way. The third point, photorespiration takes place as the chloroplast, peroxisomes and mitochondria, and dark respiration occurs in the cytoplasm and mitochondria are different. 2 - phosphoric acid occurred during photorespiration is the first product, which is a carbon atom with two chemicals, so people turn called c2 photorespiration photorespiratory carbon oxidation cycle (c2 photorespiration carbon oxidation cycle, pco ), or simply c2 cycle. In addition, there are other names photorespiration: Oxidative photosynthetic carbon cycle (oxidative photosynthetic carbon cycle), glycolic acid pathway (glycolate pathway) or c2 bypass. Third, the process Photorespiration involves collaboration between the three organelles: chloroplasts, peroxisomes and mitochondria. The whole process can be seen as adding oxygen from the rubp be decomposed into 2 - phosphoric acid and 3 - phosphoglycerate, through a series of reactions of carbon compounds in the two phosphoric acid glycolic acid to generate 3 - phosphoglycerate, which enter the Calvin cycle, students can once again become rubp. Within the chloroplast is the beginning and ending photorespiration reaction is peroxidase in vivo conversion of toxic substances, and mitochondria will be part of two molecules of glycine to serine synthesis and release part of the carbon dioxide and ammonia. Breathing in the light of ammonia generated in the process, the cell through the glutamine - glutamate cycle fast and efficient recovery of fixed re-use, this process consumes part of the atp and nadph. C3 in terrestrial plants, breathing in the light of ammonia generated in the process than to plant roots can absorb even more, to become self-plants an important part of nitrogen metabolism. And compared to the absorption of nitrate by the roots or root nodules obtained directly from the fixed means of ammonia, the ammonia fixing efficiency of light respiration to 5 to 10 times higher. Chloroplasts, peroxisomes and mitochondria close to each other, if that is the case, the substrate in the diffusion distance between organelles will be reduced, the reaction rate will naturally be faster. 1, some chloroplast The beginning of photorespiration: a molecule of oxygen molecules with a 1,5 - bisphosphate ribulose generate a molecule of 2 - phosphoric acid (2-phosphoglycolate) and 3 - phosphoglycerate (3-phosphoglycerate). Reaction from the 1,5 - ribulose bisphosphate carboxylase / oxygenase rubisco catalysis. This is a phosphoric acid molecules are stripped of phosphoric acid phosphatase acid phosphatase machine group as (glycolate). Glycolate in the chloroplast membrane transporter on the corresponding (translocator), which assist in acid to leave the chloroplast. Peroxisomal glycolate reached, it will be the hole through the protein (porin) consisting of holes (poren) into the peroxisome. The lateral view, the final stage of photorespiration also occurs in chloroplasts. Obtained by the peroxisomal glycerol acid will change to 3 - phosphoglycerate, which is also the beginning of photorespiration bisphosphate ribulose carboxylation decomposition and Calvin cycle stage of the product. 3 - phosphoglycerate enters the Calvin cycle the remaining two stages: the reduction stage (the product of a triose phosphate triosephosphate) and 1,5 - ribulose bisphosphate regeneration phase. Meanwhile, the chloroplast also be able to restore α-ketoglutarate to glutamate. This is the process of photorespiration glutamate - ketoglutarate part of the loop. Will be recycled back to glutamate with glyoxylate peroxidase in vivo role for transamination. 2, some peroxisome Peroxisomal matrix in the handling of toxic substances in the cell a special place. But through Arabidopsis (scientific name: arabidopsis thaliana) study peroxisome with than previously thought (ie, lipid degradation, photorespiration and the three major hydrogen peroxide detoxifying effect) more. Optical path of light generated by respiratory acid and hydrogen peroxide (hydrogen peroxide) are all toxic effects of substances. Even if the two substances present in low concentrations in chloroplasts, and can completely block the occurrence of photosynthesis. The reason is that acid and hydrogen peroxide will oxidize the Calvin cycle in the disulfide bond of thioredoxin, thioredoxin protein lost the ability to activate downstream. Glyoxylic acid can inhibit rubisco. In the peroxisome, the glycolic acid and oxygen into glyoxylic acid and generates hydrogen peroxide. Hydrogen peroxide is in the peroxisomal catalase (catalase) catalyst for water and oxygen. The glyoxylate will also be the participation of glutamate and generated by transamination of glycine, glutamic acid catalysis of the enzyme is glyoxylate aminotransferase. Glycine by Kong Daoyi a mitochondrial peroxisome arrive by transit to the latter to participate in the next step reaction. Serine in mitochondria is generated by peroxisomal will return, when the serine as amino donor will, through serine glyoxylate aminotransferase (serine glyoxylate aminotransferase sgat) hydroxylation into pyruvate, which In the case of hydrogen donor nadh is reduced to glycerate, return chloroplasts. And serine glyoxylate aminotransferase and glutamate glyoxylate aminotransferase reaction is catalyzed by amino acids in plants, the important process of adjustment. 3, mitochondrial part In mitochondria, two molecules of glycine in the glycine decarboxylase complex part of the role of carbon dioxide and ammonia off to produce a member of serine. Nadh generated in response to mitochondrial respiratory chain can be used for energy generation, while also reducing equivalents are supplied as the other organelles use. Glycine has a strong green mitochondrial oxidative capacity, the glycine decarboxylase complex could account for mitochondrial proteins dissolved in 30 to 50%. Glycine oxidation of non-protein content of green plants are few, or even missing. 4, the loss of photorespiration Photorespiration is more costly than the energy to carbon fixation. In the Calvin cycle, carbon dioxide would cost 3 per molecule and 2 molecules of molecular atp nadph. Suppose now the two rounds of photorespiration, and contact the Calvin cycle into account, ie, 2 molecules o2 added, calculated from the energy loss rubp back rubp. First, the whole process will release a molecule of carbon dioxide, that is, idling around the Calvin cycle, loss 3atp and 2nadph. Then the process of light respiration, glycerol kinase and nh4 + re-fix the consumption 1atp, the latter also a member of nadph. The process produces three molecules of 3 - phosphoglycerate to 3 molecules and re-generating triosephosphate part rubp, The former requires 3 molecules atp and 3 molecules nadph, which takes about 2 molecules atp. Taking into account the process of heat loss occurs there, fully, in order to balance the two molecules of carbon change in o2, the cell consumes 10.5atp and 6nadph. The following table is the participation in the two oxygen molecules, 2 molecules rubisco carboxylation and oxidation of energy loss and nadhp loss, and carbon fixation contrast. ┌ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┐ Carboxylation function │ │ │ │ oxidative │ atp │ 6 │ 10 │ │ nadph │ 4 │ 6 │ │ carbon fixed number │ 2 │ 1.4 │ └ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┘ When photorespiration is present, the number of carbon sequestration is not the time from 5 down to 3.5, reduce the efficiency of 30%. However, according to wittmann.c published studies and others, less than 1.5cm of the Weeping birch (betula pendula roth) branches in the light breathing (20% o2) and non-photorespiratory (<2% o2) conditions by measuring gas exchange found that the plants photorespiration did not have dominant influence on carbon flows. Fourth, the biochemical basis of photorespiration and the characteristics of rubisco Higher plants 1,5 - ribulose bisphosphate carboxylase from the chloroplast encoded by the eight large subunits and eight from the nuclear encoded small subunits. Contains the catalytic large subunit has all the information required, and the function of the small subunit is not known. The presence of oxygen will reduce the performance of photosynthesis, this phenomenon is named according to their discoverer W Fort effect. The phenomenon, with the oxygen in the cells play multiple roles. First: to electron acceptor oxygen will form, making the short non-cyclic electron transport chain. Second: carbon dioxide, oxygen is the corresponding competitive inhibitor of the rubisco. Biological catalysts - enzymes have several features, one of which is specific, that is a kind of enzyme catalyzed reactions usually as a response object. Known as the "substrate specificity" and "response specificity." However, photorespiration is able to occur because rubisco of the "two sides", that rubp addition to carboxylation (for rubp add-coo-groups) for photosynthesis, but also has the oxygenase function (as rubp add two oxygen atom), and rubp into photorespiration process. Can not distinguish between the enzyme active site of oxygen and carbon dioxide. Together the two gases compete for the active center of rubisco, the enzyme kinetics of the phenomenon known as "competitive inhibition", which being highly efficient catalyst in the enzyme that is rare. Although carbon dioxide in the air / oxygen ratio of 0.035% / 21%, and in the leaves of the gas chamber gas carbon dioxide concentrations lower than the outside world. But in the 25 ° c water, dissolved carbon dioxide concentration of 11μm, while the oxygen is 253μm, the ratio between 1 / 23. Taking into account the rubisco 80 times the carbon dioxide of high oxygen affinity (see Table in co2/o2 specificity), carboxylation: oxygenation effect was slightly lower than 80:23, about 4:1 to 2:1, carbon sequestration is still in surplus. Partial pressure of oxygen and carbon dioxide ratio is external factors that determine the equilibrium of rubisco. When the oxygen partial pressure of carbon dioxide increased falls, rubisco activity increased oxygen increases and oxygen into the c2 loop. In addition, the air temperature and humidity, light intensity also affect the carbon fixation rate factors. Chloroplasts in plant cells present in the matrix rubisco, as early as 3.5 billion years ago in the first batch of bio-chemical mineral nutrition occur within. Earth's primordial atmosphere was a lack of oxygen and carbon dioxide concentration in the relatively high oxygen characteristics of the enzyme plus carboxylation was suppressed significantly. Strong carboxylation beneficial to plant growth. Later to 15 million years ago atmospheric oxygen concentration, photorespiration slowly increased. At this point rubisco oxygen and carbon dioxide can no longer distinguish between the. Fifth, suppression of photorespiration is not the reason ▲ c4 plants suppress photorespiration Strategy Living in arid regions c4 plants was able to suppress photorespiration good, so they are more economical than the c3 plants. This mechanism does not involve the transformation of rubisco. c4 plant foliage has a "wreath anatomical structure" (German: kranzanatomie), plant material transfer pipe, the vascular bundle, is a circle specialized cells - cells surrounding the vascular bundle sheath, bundle sheath and then the outside is mesophyll cells. The reason that the "specialized" because the structure of bundle sheath cells of different plants and c3, bundle sheath cells and mesophyll cells present division of labor. First, bundle sheath cells, chloroplasts, and some c4 plant bundle sheath cells contain chloroplasts grana degradation, known as the non-grana chloroplasts, the chloroplast stroma lamellae contain only. In the light reactions of photosynthesis in the optical system ii (photosystem ii) is distributed mainly on the grana. Lack of basic grains can not be normal light reaction means. Therefore, no grana of chloroplast division into a special place where the dark reaction. Also, the mesophyll cells can be gas exchange with the outside world, but not the same plants with c3, c4 plants the mesophyll cells are no longer divided into spongy and palisade mesophyll, so that bundle sheath cells to exchange gases with the outside world mesophyll cells are replaced. Although the mesophyll cells and bundle sheath cells are their own cell walls are separated by suberin. But between a wide range of plasmodesmata contact, such contact between the two metabolic products made out of a possible. If the destruction of this structure, but will reduce the rate of material flow between organizations, resulting in leakage of co2 in the bundle sheath Plaza, reducing the activity of related enzymes. Visible, mesophyll cells have become a fixed place of carbon. In the tropics, the sun angle large, projected area is small, light a short distance through the atmosphere, resulting in high surface temperature, light levels. c3 plant respiration intensity of light, but also out of the Calvin cycle in the loss of fixed carbon 20% of the energy loss is very great. C3 plus stomatal opening of plants rely on frequent self-absorption of carbon dioxide to compensate for the lower rubisco efficiency, water overflow with open stomata (transpiration), water loss of plants and more natural than the c4. The water supply is changed from aquatic plants to terrestrial life after deciding factor. Not difficult to understand, c3 plants in the area is difficult and c4 plant competition. However, the weak light areas, but rarely seen c4 plants (exception: Down Spartina, scientific name: spartina townsendii). Weak light (or even become the limiting factor on the ecology), low temperature, c3 fixed before the plant can save the energy of carbon dioxide, more advantages. In summary, the pump mechanism into carbon dioxide c3 plants in tropical regions and is the current transformation c3 photosynthetic efficiency of plants in one direction. Sixth, the artificial control of photorespiration Some people think that inhibition of photorespiration can improve the plants, especially crops, the amount of carbon fixed, so as to achieve the purpose of food production. So the scientists have made in this respect a lot of research and look forward to suppress photorespiration. 1, genetic engineering and transgenic technology The focus of research is rubisco. Researchers seek to structure or by changing the role of rubisco environment itself to increasing its direction in the specificity of photosynthesis. Through genetic engineering and the combination of transgenic technology, there are three attempts. The first two focus on improving the efficiency of rubisco carboxylation, which directly reduce the oxygenase activity, and by adding the enzyme increased rubisco c4 bypass around the concentration of carbon dioxide. The third method is by controlling the light breathing other enzymes to achieve the objective of reducing photorespiration. In general, these methods have not yet achieved very tangible results, sometimes even negative results. ▲ try a Scientists have improved in the three directions rubisco. First, import the high quality of plant rubisco. Study found that the red algae rubisco carboxylase / oxygen specificity was actually three times the food crops. Two red algae cyanidium caldarium and galdieria partita have rubisco, its relative specificity was 2.5 times higher plants. Therefore, the rubisco was the galdieria partita quality system conducted by the original method into tobacco plant cells. Then the experimenter measured over a period of time after the plants of the rubisco large subunit was significantly increased, but no significant increase of photosynthetic activity. May be due to the lack of tobacco cells plasmid partner fibroin (chaperon), which is the correct folding of rubisco, the key to its effectiveness and to play. In the small subunit, the renovation project in its infancy. Some people in the mutant cyanobacteria (cyanobacteria) and small subunit genes of green algae made after trial, the small subunit is possible to improve the efficiency of carbon fixation and differentiation of oxygen / carbon dioxide has its role. Also possible that genetic engineering is the small subunit of the large subunit of genetic engineering than the current transformation of a more viable strategy. Third, changes in rubisco activity by activating protein. Scientists found that rubisco activation - deactivation of rubisco activation state and a known protein (rubisco activase) related to in vitro experiments, this protein is obviously not stable. c3 plants in the 30 to 35 degrees C environment, decreased ability to accumulate carbon. This process is reversible, that is, as long as the temperature dropped, the carbon fixation capacity of plants will be restored. It was thus activating proteins and plant photosynthetic rubisco capacity with temperature fluctuations of this phenomenon. More and more literature to support this hypothesis. It is noteworthy that, c4 plants tidestromia at 48 ° c in the environment to reach their maximum photosynthetic capacity, may be related to the plant rubisco activation of protein is more stable than most higher plants, preferably in the high temperature environment to play the role. Although still in the hypothesis stage, but scientists have started to experiment. They use heat-resistant gene mutations in rubisco activation of protein manufacturing. Produced in vitro activation of heat rubisco protein is isolated and can be implanted in Arabidopsis. These experiments raise plants in a small range of temperature conditions, the leaf surface area is twice that of wild plants, photosynthetic efficiency increased by 30%. Although these results are preliminary, but people have seen this method in the improvement of plant photosynthesis in the high temperature environment has potential. ▲ try two Increased concentration of carbon dioxide can reduce the light respiration rate, as c4 plant's carbon dioxide pump. The pump mechanism into carbon dioxide plant c4 c3 plant is one of the current research. In fact, back in c4 mechanism is not clear how long, someone committed to the fine traits of plants c4 c3 transmission to the plant, but failed. In the late 20th century early 21st century, c4 bypass 4 of enzymes have been cloned into the expression of c3 plants and was successful. For example, plants such as corn c4 isolated genes of these enzymes was cloned into the target plant rice. Success of these genes have a high level of expression. Although scientists from a number of interesting phenomena observed, but did not receive any specific aspect has improved significantly. The high level of expression of these enzymes and the single no significant impact on the growth of rice. Which nadp-high levels of malic enzyme plant development has lead to stagflation and the leaves turn white. It is important that, c4 plant carbon dioxide pump mechanism is not merely the result of enzyme function, as well as the structural basis of their anatomy, that the "ro_set_te anatomy." At present, research efforts in that regard are not taken into account such an important factor, just look at the c3 c4 plant cells to establish a plant enzyme systems. Research in this direction can be seen there is still much room for improvement. There is also a method of initial success, is to require a high degree of carbon dioxide in the ictb cyanobacteria genes into higher plants. Although it was suggested that the gene has the function of the accumulation of inorganic carbon, but the role of general ictb still unknown. Now scientists have succeeded in tobacco (nicotiana tabacum) cells of cyanobacteria Synechococcus pcc7942 (synechococcus pcc7942) ictb gene, and observed that the tobacco in a certain level of carbon dioxide (but not the level of carbon dioxide saturation levels) show more high photosynthetic efficiency. This result also accepted Anabaena pcc7120 (anabaena pcc7120) ictb gene in Arabidopsis was observed. In the low humidity environment, arabidopsis thaliana transgenic Arabidopsis plant growth faster than the wild, dry weight even more. This increase in photosynthetic efficiency and carbon break point down shows ictb for the rubisco gene may increase the concentration of carbon dioxide has a role. These experimental results indicate that the introduction of ictb for crop genes may be hot, arid areas can increase crop yields. The gene was put into commercial use requires a premise that should be clearly recognized that the gene expression of proteins in cells in the cell's position and role. ▲ try three A third attempt is to change the other enzymes involved in photorespiration photorespiration in order to achieve the purpose of suppression. This can be added by genetic engineering or photorespiration inhibitor achieved. See respiratory inhibitors on the light post. This attempt is based on the rationale for chemical equilibrium: a chemical reaction a → b, the initial reaction, a concentration of large, changing the b. However, b will be returned through the reverse reaction a, b, is only the beginning of a much lower concentration than the reaction is a tendency to b. However, if large enough concentrations of b, b to a, and a reaction was to b like the frequent reaction was stopped on the macro. Then observe the reaction chain a → b → c. If b → c is very slow, or even suppressed, b the concentration will be high. the reaction between a → b can not be, can only be maintained in the balance. Such an attempt to try to resolve the energy, rubp and nadph respiratory pathway in the light is wasted on the issue. However, due to reaction intermediates can not be stacked, would cause damage to cells. Experiment proved that, through genetic modification in inhibiting certain enzymes in photorespiration plants can not grow in normal air. In antisense plants, glycine decarboxylase activity is suppressed, will lead to plant wild strains of day-glycine 100 times higher than that, then there photosynthetic rate and growth rate slowed down. Some plants, the serine hydroxymethyl transferase (serine hydroxymethyl transferase shmt) reduced the activity of the more obvious will affect plant growth, especially in high-light environment. Serine hydroxymethyl transferase activity was severely reduced in plants can not survive in normal air, even in normal light does not work, but was able to survive in the high carbon dioxide. 2, increased partial pressure of carbon dioxide around the plant, reducing oxygen partial pressure As noted above, rubisco the carboxylase / oxygenase activity by which atmospheric carbon dioxide and oxygen partial pressure ratio in. 21% of the oxygen is also in associated with 300 μl / l co2 cases, photosynthetic efficiency will drop 41%, of which two-thirds because the centers of oxygen caused by competition for rubisco, and the other third is the loss caused by photorespiration . When the carbon dioxide concentration and then decreased to 50 μl / l, the photosynthetic efficiency will drop 92% this time, two-thirds of the loss was caused by photorespiration. 3, the use of inhibitors of photorespiration Photorespiration glycolate is the second product of the process, scientists can inhibit certain chemical agents have to make a follow-up reactions of photorespiration can not proceed, and thus inhibit the role of photorespiration. The main inhibitor of photorespiration are the following: ① α-hydroxy sulfonate, can inhibit the activity of glycolate oxidase, blocked the oxidation of glycolic acid, follow-up reaction is slowed down, on the other hand this will lead to increased concentrations of glycolic acid in 1,5 - bisphosphate ribulose → glycolic acid in the reaction, the reaction equilibrium shifts to the reactants, photorespiration was suppressed. But it is worth noting that, when after a period of time, plant carbon sequestration effect is not significantly improved, presumably because of accumulated acid toxicity to plants caused the result. ② sodium bisulfite, the same effect on glycolate oxidase. To 100mg / l of sodium bisulfite spraying soybean leaves, 1 to 6 days, 15.6% average increase photosynthetic rate, photorespiration was inhibited up to 32.2%. ③ 2,3 - epoxy acid, some people think it will act on the glutamate - glyoxylate aminotransferase, the purpose to suppress photorespiration, but not widely confirmed. Note that, at present the majority of respiratory inhibitors on optical data from the laboratory, has not been widely used and proven, and scientists have yet to find a way to have no side effects, a specific inhibitor of rubisco oxygenase. 4, _select_ion of crops with low photorespiration Seven, the positive effect of photorespiration For c3 plants, the light breath like a piston. When the outside temperatures, and need to close the stomata of plants to prevent excessive water loss, the leaves will reduce the concentration of carbon dioxide, which leads to the stagnation of the dark reaction. Dark reaction is not time consuming excess energy atp, which resulted in the light reaction occurs in the probability of singlet oxygen increases. The singlet oxygen is very lively, the photosynthesis of leaf cells would be widespread destruction device. For transgenic plants and the recent _insert_ion mutant studies show that light aerobic respiration of plants in the environment must be the biochemical processes. In conclusion, plants in high light, drought and high salt environment will occur in tropical photoinhibition and photorespiration is likely to mitigate the impact of the mechanism. Produced during photorespiration two amino acids: glycine and serine can be used in plant metabolism. All these findings led to the discussion of plant science, whether the plant should be reduced to light respiratory efforts. VIII determination The general method can not measure gas exchange photorespiration carbon dioxide / oxygen usage. There are several methods available: ① light on the plants, a sudden stop occurs when so-called "carbon dioxide burst" on behalf of the rate of light respiration rate of plants. ② let the plants for photosynthesis in hypoxic environment, this time can not breathe. Plants placed in the atmosphere as plants, according to the difference between the two states projected rate of photorespiration. ③ with a carbon 14 isotope of carbon dioxide in the supply of plants for photosynthesis. Then in the dark without carbon dioxide to pass into the plant air, measured breathing again. And then tested once in the light conditions. Can be calculated according to the difference between the two. ④ photosynthetic rate of carbon dioxide and carbon dioxide curve to move to 0, the location of photosynthetic rate is negative, you can read out the light respiration rate.
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光呼吸 百科辞典
guanghuxi Photorespiration photorespiration Light green cells of plants occur in the absorption of oxygen and release carbon dioxide process. Photorespiration and photosynthesis occur simultaneously, the mechanism of normal cells in the light and dark respiration can be significantly different. Photorespiration substrate is glycolic acid, which is in the Canon of chloroplast ribulose bisphosphate carboxylase ribulose bisphosphate catalyzed oxygenase reaction occurs to form, after the body was transferred to the peroxide oxidation of glyoxylate. This is the light breathing oxygen process. Glyoxylate into glycine and further transferred to the mitochondria occurred after the break, release CO □, which is the release of carbon dioxide in the process of photorespiration. In the light breath, glycolic acid because it is formed by the photosynthetic carbon cycle intermediates of photosynthetic products transformed from the former, it will affect the production of the accumulation of photosynthetic products, which after decomposition and the photosynthetic fixation of carbon dioxide is discharged, photosynthetic fixed effect of the loss of energy also, so photorespiration, photosynthetic efficiency. The strength of plants and plant photorespiration structural features and external conditions. C □ vascular plant leaves is closely linked to the bundle sheath cells containing chloroplasts surrounded by bundle sheath cells of carbon dioxide released during photorespiration can be collected again fixed, so the light respiration rate is very low. C □ plants lack this structure, so the intensity of light respiration. In addition, because the substrate of photorespiration glycolate is formed in the light conditions, so the light enhanced respiration and photosynthesis while enhancing the time. Increase in the concentration of oxygen in the air but also can increase photorespiration; and increased carbon dioxide concentrations would be suppressed photorespiration. (Ming-Qi Li)
