L16_Savannas_C3_C4_Photosynthesis_comp

C3 wheat rice rye c4 corn sorghum sugarcane note

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Unformatted text preview: herbivory, soil quality, etc. desert stable transi=onal rainforest unstable Gross Primary Produc=vity (GPP): The total amount of carbon fixed, regardless of whether that carbon is then respired by the photosynthesizer, or stored into =ssue growth, energy reserves, etc. (Units: moles carbon per unit =me (example: mol/yr)). Or ecosystem- specific GPP can be given as moles per area per =me: mol/(m2*yr) Photosynthesis: CO2 + H2O à༎ CH2O + O2 Net Primary Produc=vity (NPP): The net amount of fixed carbon that is available to the ecosystem (i.e., the surplus fixed carbon: carbon that goes into plant growth, and is not immediately respired by the plant). Units: moles carbon per unit =me (example: mol/yr). Or ecosystem- specific NPP can be given as moles per area per =me: mol/(m2*yr) Photosynthesis: CO2 + H2O à༎ CH2O + O2 To meet its energe=c requirements, the plant will need to respire some of the fixed carbon: CH2O + O2 à༎ CO2 + H2O Any excess (or lehover) CH2O contributes to NPP. This carbon can be used by other organisms as an energy source: Example: People ea=ng crops: CH2O + O2 à༎ CO2 + H2O The three photosynthetic pathways of land plants" C3: primarily trees, shrubs, herbs, cool- season grasses (~80% of primary produc=vity) C4: primarily warm- season grasses (~20% of primary produc=vity) CAM: Crassulacean Acid Metabolism (cactus and succulents) (of minor importance to global carbon cycle) Crop grasses: C3 or C4? C3 wheat rice rye C4 cor...
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This document was uploaded on 03/26/2014 for the course GEC AS.270.103 at Johns Hopkins.

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