Main monitoring indicators: net photosynthetic rate (PN), transpiration rate (TR), stomatal conductance (GS) and other gas exchange parameters were measured, At the same time, atmospheric CO2 concentration (CA), intercellular CO2 concentration (CI), photosynthetically active radiation (PAR), atmospheric temperature (TA), leaf surface temperature (TL), air relative humidity (RH) and other parameters were measured, and each leaf was read three times. WUE = pN / TR, LS = 1 - CI / ca.
When the depth of groundwater is shallow, the photosynthesis of Populus euphratica is mainly affected by the comprehensive effects of atmospheric CO2 concentration, intercellular CO2 concentration, photosynthetically active radiation, and leaf temperature. However, as the groundwater level decreases, atmospheric CO2 concentration and photosynthetically active radiation become the main factors limiting the photosynthesis of Populus euphratica. This is because when the groundwater in lowlands is buried deep, the groundwater supply is sufficient, and the leaves are not limited by water supply. When the photosynthetically active radiation is strong, the temperature and leaf temperature are relatively high, and the relative humidity of the air is low. At this time, photosynthesis and transpiration are strong, and stomata mainly adapt to strong transpiration by increasing stomatal conductance, that is, reducing stomatal resistance. At the same time, CO2 in the air continuously enters cells through open stomata, and together with CO2 between cells, becomes the raw material for photosynthesis, resulting in a decrease in the concentration of CO2 in the air and between cells. This is the CO2 supply limitation that often causes photosynthesis inhibition in photosynthesis. But when subjected to water stress, the supply of CO2 is no longer the main reason limiting photosynthesis. When the photosynthetically active radiation increases, the net photosynthetic rate, transpiration rate, and stomatal conductance all increase. When the supply of CO2 concentration is still sufficient, photosynthesis will slow down due to insufficient water, another necessary raw material for photosynthesis
Use the LI-6400 portable photosynthesis analyzer to maintain a flow rate of 400 μ mol/s and a leaf temperature of 26 ° C. Use a CO2 injection system to maintain a CO2 concentration of 360 μ mol/mol or 720 μ mol/mol in the reference chamber, and set the photosynthetically active radiation (PAR) to 2000, 1500, 1200, 1000, 500, 300, 50, 0 μ mol/(m2? S) using the 6400-02B LED light source. Select 12 healthy and mature leaves from each Populus euphratica plant towards the upper and middle parts in the east, south, west, and north directions. From 8:00 to 20:00, use a photosynthesis analyzer Li 6400 (Li 6400, LiCOR, Lincoln, NE, USA) every 2 hours
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CSTR:11738.11.ncdc.nieer.2020.1526
10.12072/ncdc.NIEER.db0026.2020
