Photosynthesis carbon dioxide concentration

For some high growth-rate biomass species, the carbon dioxide concentration in the air among the leaves of the plant often is considerably less than that in the surrounding atmosphere. Photosynthesis may be limited by the carbon dioxide concentrations under these conditions when wind velocities are low and insolation is high. 

Nearly all of the oxygen found on Earth today is produced by biological activity. During the process of photosynthesis, carbon dioxide and water react in the presence of chlorophyll to produce carbohydrates and oxygen. Scientists believe that oxygen was essentially absent from the earth s atmosphere when the planet was first created. As life developed on Earth and photosynthesis became more common, the rate of production increased until the present concentration of oxygen in the atmosphere, the oceans, and the crustal rocks was reached about 580 million years ago. 

Considerable uncertainty surrounds the short- and long-term response of biota to altered temperatures and carbon dioxide concentrations in the atmosphere. Although enhanced photosynthesis is observed in some species under increased atmospheric C02 concentrations, unpredictable species changes and replacements are likely under altered climate. If the net effect of biotic change... 

Figure 1.1 shows the increase in the concentration of carbon dioxide in the atmosphere since the start of fossil fuel use. During the summer in the northern hemisphere, the carbon dioxide concentration decreases because of plant photosynthesis. The decrease is in the range of 5 to 15 parts per million. In the fall, this carbon dioxide is largely returned to the atmosphere. The figure shows the average for the year. Values beyond the year 2000 are projected as a simple continuation of current trends. The Kyoto Treaty line will be addressed later in this chapter. 

Ideally, the C-4 plant species would represent the best prospects for controlled or greenhouse photosynthesis from added carbon dioxide sources. Unfortunately, there is an upper limit to the carbon dioxide concentrations that can be utilized in greenhouse gases. Whereas normal atmospheric air may contain about 340 pi of carbon dioxide per hter (340 parts per million, or ppm), or 0.000340 mole fraction, or say 0.034 volume percent, the upper limit is around KXX) pi of carbon dioxide per liter (or 1000 parts per million, or ppm), or 0.001 mole fraction, or 0.1 volume percent, whereby toxicity occurs (Salisbury and Ross, 1985, p. 224). 

Delgado, E., M.A.J. Parry, D.W. Lawlor, A.J. Keys, and H. Medrano Photosynthesis, ribulose-l,5-bisphos-phate carboxylase, and leaf characteristics of Nicotiana tabacum L. genotypes selected by survival at low carbon dioxide concentrations J. Exp. Botany 44 (1993) 1-7. Demandre, C., A. Iremolieres, A. Justin, and P. Mazliak Analysis of molecular species of plant polar lipids by high-performance and gas liquid chromatography Phytochemistry 24 (1985) 481 85. 

Respiration is essentially the converse of the process of photosynthesis. If the two processes occur concurrently, then the rate of photosynthesis as actually observed (net photosynthesis) will be less than the total rate (gross photosynthesis) by an amount equal to the rate of consumption of the products of photosynthesis in respiration. At certain low light intensities or carbon dioxide concentrations the two processes balance so that there is no net gas exchange and the photosynthetic organism is then said to be at its compensation point. It has usually been assumed, according to Fogg... 

In this activity, you will prepare two test samples containing an indicator and different amounts of CO2. As CO2 is consumed to produce oxygen, the color of the solution changes. By observing how quickly the color change occurs, you can qualitatively evaluate the dependence of photosynthesis on carbon dioxide concentration. Because oxygen gas is colorless and odorless at room temperature and pressure, methylene blue is used as an indicator. Oxygen gas is the only gas that removes the color from methylene blue. 

How does carbon dioxide concentration affect the rate of photosynthesis ... 

Infer the effect of carbon dioxide concentration on photosynthesis. 

The manufacture by plants of carbohydrates and oxygen from carbon dioxide and water in the presence of chlorophyll with sunlight as the energy source. Oxygen and water vapor are released in the process. Photosynthesis is dependent on favorable temperature and moisture conditions as well as on the atmospheric carbon dioxide concentration. Increased levels of carbon dioxide can increase net photosynthesis in many plants, phytoplankton... 

Photosynthesis is the process that provides energy to all anabolic and catabolic processes in ecosystems. The rate at which plants assimilate CO2 in the field may be quite different from optimal conditions in the test tube or in growth cabinets. The rate depends on the environmental conditions of the habitat which determine to what extent the genetic capability of a plant can actually be used for photosynthesis. The main factor restricting photosynthesis in the field is the availability of light. But, other factors my become just as rate 1imitating, such as atmospheric carbon dioxide concentration, air humidity and temperature, and water or nutrient supply from the soil. Time is an additional important factor which influences the carbon balance via plant age but also by deterimining the dose of stress. 

The early work in photosynthesis was based on the assumption that carbon dioxide fixation was a process unique in green plants, and studies were made on the effect of various external factors such as light intensity, light quahty, carbon dioxide concentration, and temperature. Certain internal factors were also recognized as affecting photosynthesis. Many fundamental studies on photosynthesis were concerned with the chemistry of the chlorophyll molecule. Enzymes were studied, and attempts were made to carry out cell-free photosynthesis by conventional biochemical techniques. While these studies contributed a great deal of information regarding the photosynthetic reaction, they did little to elucidate the mechanism of the process. 

Kinetic studies indicated that photos3mthesis is dependent upon a number of external and internal factors. Of the external factors, carbon dioxide concentration, light, and temperature are the most important, whereas the chlorophyll concentration is probably the most important internal factor. The concentrations of various enzymes as well as certain undefined protoplasmic factors have also been suggested as limiting photosynthesis. 

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