The greenhouse effect. The consequences of this increase in atmospheric CO2 are under intense Certain gases in the atmosphere, particularly CO2 and methane, play the same role as the glass roof in a greenhouse. The increased CO2 concentration and temperature associated with the greenhouse effect can influence photosynthesis. At current atmospheric CO2 concentrations, photosynthesis in C3 plants is CO2 limited (as we will discuss later in the chap- ter), but this situation could change as atmospheric CO2 con-centrations continue to rise. Under laboratory conditions, Intercellular air space resistanceStoma Stomatal poreBoundary layer resistance CO2 Stomatal resistance Liquid phase resistanceBoundary layer most C3 plants grow 30 to 60% faster when CO2 concentra-tion is doubled (to 600–700 ppm), and the growth rate FIGURE9.17 Points of resistance to the diffusion of CO2from outside the leaf to the chloroplasts. The stomatal e changes depend on nutrient status (Bowes 1993). In some plants the enhanced growth is only temporary.For many crops, such as tomatoes, lettuce, cucumbers, is the major point of resistance to CO2 diffusion. por and roses growing in greenhouses under optimal nutrition, carbon dioxide enrichment in the greenhouse environment results in increased productivity. The photosynthetic per-formance of C3 plants under elevated CO2 is enhanced because photorespiration decreases (see Chapter 8).
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