Photosynthesis of <Emphasis Type="Italic">Populus euphratica</Emphasis> in relation to groundwater depths and high temperature in arid environment,northwest China |
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Authors: | H H Zhou Y N Chen W H Li Y P Chen |
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Institution: | (1) Key Laboratory of Oasis Ecology and Desert Environment, Xinjiang Institute of Ecology and Geography, CAS, Urumqi, 830011, People’s Republic of China;(2) Institute of Resources and Environmental Science, Xinjiang University, Urumqi, 830046, People’s Republic of China |
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Abstract: | The photosynthetic characterization of Populus euphratica and their response to increasing groundwater depth and temperature were analyzed based on net photosynthetic rate (P
N), stomatal conductance (g
s), intercellular CO2 concentration (C
i), transpiration rate (E), water use efficiency (WUE) and stomatal limitation (Ls) measured by a portable gas-exchange system (LI-6400) in the lower reaches of the Tarim River. Light-response curves were constructed to obtain light-compensation and light-saturation
points (LCP and LSP), maximum photosynthetic rates (P
max), quantum yields (AQY), and dark respiration rates (R
D). The growth condition of P. euphratica, soil moisture, and groundwater depth in the plots were analyzed by field investigation. The results showed that the growth
condition and photosynthetic characterization of P. euphratica were closely related to groundwater depth. The rational groundwater depth for the normal growth and photosynthesis was 3–5
m, the stress groundwater depth for mild drought was more than 5 m, for moderate drought was more than 6 m, for severe drought
was more than 7 m. However, P. euphratica could keep normal growth through a strong drought resistance depended on the stomatal limitation and osmotic adjustment when
it faced mild or moderate drought stress, respectively, at a normal temperature (25°C). High temperature (40°C) significantly
reduced P
N and drought stress exacerbated the damage of high temperature to the photosynthesis. Moreover, P. euphratica would prioritize the resistance of high temperature when it encountered the interaction between heat shock and water deficit
through the stomata open unequally to improve the transpiration of leaves to dissipate overheating at the cost of low WUE,
and then resist water stress through the osmotic adjustment or the stomatal limitation. |
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