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Comparative Study of Photosynthetic and Chlorophyll Fluorescence Characteristics of Populus euphratica and P.pruinosa

The photosynthetic and chlorophyll fluorescence characteristics of Populus euphratica and P.pruinosa were comparatively studied.The results showed that the net photosynthetic rates of P.euphratica and P.pruinosa presented a single-peak curve and the Pn of P.euphratica appeared lower at 12:00;Their stomatal conductance appeared to vary in a single-peak curve and their intercellular CO_2 concentrations appeared to vary in a V-shaped curve.Under same experimental conditions,the net photosynthetic rate and stomatal conductance of P.euphratica appeared higher than those of P.pruinosa and reached their peaks at 10:00,and the intercellular CO_2 concentration of P.euphratica appeared lower than that of P.pruinosa and always reached its lowest point at 14:00.After sufficiently adapting to darkness,the chlorophyll fluorescence parameters such as Fo,Fv/Fo,and Fv/Fm of P.euphratica leaves were significantly higher than those of P.pruinosa leaves.The measurement of the daily chlorophyll fluorescence parameters with sunlight as the photochemical light indicated that the ΦPSⅡ,ETR and qP of P.euphratica were higher than those of P.pruinosa but the NPQ of the former was lower than that of the latter.It is because of these photosynthetic and chlorophyll fluorescence differences between P.euphratica and P.pruinosa that P.euphratica is more capable of adapting to the environment with strong sunshine,high temperature and low air humidity in arid and desert regions,and this is one of the physiological reasons why it has a higher net photosynthetic rate.