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Irrigation Medicine Case Study

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The effects of different irrigation treatments and CO2 concentrations on the stomatal conductance (gs) and transpiration rate (Tr), of maize are shown in Fig. 4a, b, c, d. The figure shows that gs and Tr decreased with the enrichment of CO2 concentrations under both RI and DI. Compared with RI400, gs and Tr were 27 and 23% lower under DI400; for the elevated CO2 concentrations, gs and Tr were 22-36 and 25-26% lower under DI when compared with RI. Relative reductions in gs and Tr due to the DI treatment were therefore more pronounced along with elevated CO2 concentrations.
Compared with RI400, RI550-RI700-RI900 decreased gs by 13, 22, and 33%, and Tr by 12, 23, and 38%, respectively. Compared with DI400, DI550-DI700-DI900 decreased gs by 8,
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While compared with DI400, DI550-DI700-DI900 increased Tleaf by 2.4, 4.0, and 5.7%, respectively. Hence the relatively increase in Tleaf caused by elevated CO2 concentrations was higher under DI than under RI. Leaf temperature was highly correlated with Tr under most conditions (Pallas et al., 1967). And it was obvious to see that the higher Tr was shown in the markedly lower Tleaf, and vice versa, namely the so called transpiration cooling effect (Pallas et al., 1967). So when the elevated CO2 concentration reduced Tr, the Tleaf increased. Also with decrease in soil water in DI condition, Tr was decreasing; meanwhile, Tleaf rose more remarkable than that only under elevated CO2 conditions. As that Tr cannot be ignored in the changes of Tleaf (Cook et al., 1964; Gates, 1964), and Tr changes was more pronounced under DI, so as to the changes of Tleaf.
Figure 4 e and f show the effect of different irrigation treatments and CO2 concentrations on net photosynthetic rate (Pn). Net photosynthetic rate increased with the enrichment of CO2 concentration. Compared with RI400, Pn was 24% lower under DI400; for the elevated CO2 concentrations, Pn was 15-20% lower under DI when compared with RI. Relative reductions in Pn due to the DI treatment was therefore weakened along with elevated CO2 concentrations.
Compared with RI400, RI550-RI700-RI900 increased Pn by 30, 45, and 59%, respectively, while compared with DI400, DI550-DI700-DI900 increased Pn by 37, 51, and 77%,
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