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>There is further observational evidence since AR4 that response to a change in CO2 depends on plant type: C3or C4(DaMatta et al., 2010). The effect of increase in CO2 concentration tends to be higher in C3 plants (wheat, rice, cotton, basedbean, sugar beets, and potatoes) than in C4 plants (corn, sorghum, sugarcane), because photosynthesis rates in C4 crops are less responsive to increases in ambient CO2 (Leakey, 2009). The highest fertilization responses have been observed in tuber crops, which have large capacity to store extra carbohydrates in belowground organs (Fleisher et al., 2008; Högy and Fangmeier, 2009). There is observational evidence, new since AR4, that the response of crops to CO2 is genotype specific (Ziska et al., 2012). For example, yield enhancement at 200 ppm additional CO2 ranged from 3 to 36% among rice cultivars (Hasegawa et al., 2013). FACE studies have shown that the impact of elevated CO2 varies according to temperature and availability of water and nutrients, although the strong geographical bias of FACE studies toward temperate zones limits the strength of this evidence. FACE studies have shown that yield enhancement by elevated CO2 is limited under both low (Shimono et al., 2008; Hasegawa et al., 2013) and high temperature. Theory suggests that water-stressed crops will respond more strongly to elevated CO2 than well-watered crops, because of CO2-induced increases in stomatal resistance. This suggests that rain-fed cropping systems will benefit more from elevated CO2 than irrigated systems.
tl;dr whether a plant benefits from higher CO2 depends on the plant and where/how it's grown
