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Background Information Click here to return to C3/C4 home page A Study of the Roles and Responses of C3 and C3 Plants to Global Warming and Increased Greenhouse Gases
Introduction: The concentration of CO2 in the atmosphere is increasing. A 1970 study by MIT predicted a 20% increase by 2000. Since 1980, global warming as a result of this increase, has become a major political and scientific issue. Such rapid and extreme temperature fluctuations would have more impact on photosynthesis and survival of plants than doubling in atmospheric CO2. Through a study of ancient ice cores from Antarctica, both the concentration of CO2 in the atmosphere and global mean temperature can be determined for the past 160 years of the Earth’s history. By examining the graphs, Global Average Temperature and Atmospheric Carbon Dioxide Concentration over this period, it is quite evident that the two levels are related. For the most part, the temperature and concentration mirror each other (Woods Hole, 1999)To learn more about:
Follow this link- http://www.whrc.org/Globalwarming/warmingearth.htm
Evidence from 1860 t0 2000 indicates a continuous increase in temperature. The hottest years in the past history have all occurred since 1980 with 1997, 1995 and 1990 being the hottest. In 1995, 465 people died from heat related deaths in Chicago and 300 died in India. In 1969, the global mean temperature was 66 ° C. The average surface temperature of the Earth has increased 1 ° F in the past century. Surface temperature is projected to increase 1.8-6.3° F in the next century. Sea level has risen 4-10 inches in this century and is predicted to rise 6.37 inches in the next century.Ice Core Data from 1860 to 1960 showed a continuous increase in the CO2 concentration in the atmosphere and data from Hawaii (Mauna Loa) from 1960 to 2000 verifies this increase. By examining the graph, one sees a direct correlation between an increase in CO2 concentration and temperature change on Earth over 150 thousand years. Findings demonstrate that rising global temperatures are expected to raise sea levels and change precipitation and other local climate conditions. Changing regional climate could alter forests, crop yields and water supplies. It could also threaten human health and harm birds, fish, and many types of ecosystems. Deserts may expand into existing range lands. Increasing levels of carbon dioxide may cause more harm to marine coral reef communities than previous research indicated. Freshwater recreational fishing opportunities will be disrupted and cold water fish habitat could be reduced or lost in many states. Climate change will affect the life cycles for many types of wildlife that depend on temperature to signal migration and breeding. Studies show that some species of birds, butterflies, and amphibians are already migrating and breeding earlier than expected. Plants can be categorized photosynthetically as C3, C4, and CAM. Most plant species globally are characterized by C3 photosynthesis, but C4 and CAM pathways represent evolutionary advancements over the ancestral C3 pathway. All C4 plants have a significant advantage over C3 plants under low atmospheric CO2 (Ehleringer J. and B. Heliker, 1997). C3 plants (e.g., soybean, wheat, and cotton), whose carbon-fixation products have three carbon atoms per molecule, show a greater increase in photosynthesis with a doubling of CO2 concentration and less decrease in stomatal conductance. This results in an increase in leaf-level water-use efficiency. C4 plants(e.g., maize and sorghum), whose carbon fixation products have 4 carbon atoms per molecule, show little photosynthetic response to increased CO2 concentration above 340 ppm but show a decrease in stomatal conductance. This results in an increase in photosynthetic water-use-efficiency. The anatomy of the C4 leaf show advancements over the C3 leaf in that photosynthesis takes place in the bundle sheath instead of the mesophyll cell in C3 plants. Ecological Characteristics of C3 and C4 Plants: Plants need energy, water and interfaces where solids, liquids and gases interact to promote growth, development and reproduction. C3 and C4 plants respond differently to temperature, moisture, light intensity and environmental factors to carry out life processes. Table 1. Comparison between C3 and C4 Plants. Modified from Beadle, C.L., et.al. 1985. C3 C4
Man’s direct impact on the ecology of an area is evident when he landscapes with plants that are not naturally adapted to the climatic and soil conditions. Or indirectly, man’s behaviors create additional stressors that may cause the migration of alien species that replace the native ones. As a result - diversity, dominant species, proportion of species, feeding relations of animals and plants, as well as the temporal conditions of the area - may change. The Function of C4 Photosynthesis and Evolution/Selection: C4 plants evolved under conditions of higher temperatures and lower CO2 concentrations. Species that adapt to high temperatures and are resistant to lower water availability could migrate to newly created drier habitats and succeed other native plants that have not adapted to these conditions. As a result, the carbon cycle of the area would change as the temperature and light reaching the earth increase . Because of their rapid growth rate and higher biomass, C4 plants may be the choice for the agricultural community. These plants would thrive under higher temperatures and lower water availability. This in turn would impact the distribution, migration and evolution of invertebrates and vertebrates that graze on these plants. |
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The Woodrow Wilson National
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