To determine the truth about the model of carbon recycling by plants in the carbon cycle, consider the following statements:
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Photosynthesis: Plants take in carbon dioxide (CO₂) from the atmosphere and use it, along with sunlight and water, to produce glucose (C₆H₁₂O₆) through photosynthesis. This process is the primary way carbon enters the biosphere.
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Respiration: When plants, and other organisms, respire, they convert glucose back into carbon dioxide, releasing energy in the process. This CO₂ is then returned to the atmosphere.
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Decomposition: When plants and animals die, decomposers break down their organic matter, which also releases carbon back into the soil and atmosphere as CO₂.
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Carbon Reservoirs: Plants are a significant reservoir of carbon; they store carbon in their biomass (trunks, branches, leaves, and roots), and through various processes, this carbon can be released back into the atmosphere or soil.
Therefore, one true statement about the model of the carbon cycle relating to plants is that "Plants absorb carbon dioxide during photosynthesis, converting it into organic carbon, which is then recycled back into the atmosphere through respiration and decomposition." This illustrates how carbon is continuously cycled between the atmosphere, living organisms, and the soil.