Response of Photosynthetic Characteristics and Water Use Efficiency to Drought Stress of Caragana korshinskii in Desert

Taking the Caragana korshinskii shrub in Hobq desert as the study object, the water supply and drought degree of soil were controlled manually, the variation characteristics of photosynthetic characteristics and water use efficiency of C. korshinskii leaves under different soil water content were studied, and the response mechanism of C. korshinskii shrub to drought stress was analyzed with Li−6800 portable photosynthesis system. The results showed that the net photosynthetic rate of C. korshinskii leaves ranged from 2.02–44.80 μmol/(m²·s), the transpiration rate ranged from 0.94–23.41 mmol/(m²·s), the stomatal conductance ranged from 0.02–1.09 mol/(m²·s), the intercellular CO₂ concentration ranged from 238.12–323.05 μmol/mol, all the 4 indexes decreased obviously with the deepening of drought, and photosynthesis was restricted. Soil water content was significantly positively correlated with the net photosynthetic rate, transpiration rate, stomatal conductance and intercellular CO₂ concentration of C. korshinskii leaves. The water use efficiency of C. korshinskii was negatively correlated with total solar radiation, photosynthetic effective radiation and transpiration rate, in different degrees of drought, it showed severe drought (3.35 μmol/mmol) > moderate drought (2.87 μmol/mmol) > mild drought (2.08 μmol/mmol) > extreme drought (2.15 μmol/mmol), and had the best water use efficiency when soil water content ranged from 7%–9%.