Abstract: Taking one-year old Elaeagnus oxycarpa seedlings as test materials, this paper studied their root activity and leaf cell membrane permeability, relat\ive water content, photosynthetic pigment contents, and photosynthetic parameters at different soil relative moisture contents under natural drought condition. When the soil relative moisture content decreased from 70% (CK) to 40%, the E. oxycarpa seedlings root activity and net photosynthetic rate increased gradually and reached their maximum (1178 μg·g^-1·h^-1 and 21.9 μmol·m^-2·s^-1, respectively), photosynthetic pigment contents increased stably, transpiration rate and water use efficiency did not show any significant difference, and cell membrane permeability kept at a low level.When the soil relative moisture content decreased from 40% to 20%, the leaf relative water content was still higher than 50%, cell membrane permeability maintained at a low level, root activity and photosynthetic pigment contents remained high, and other photosynthesis parameters decreased slowly. When the soil relative moisture content decreased from 10% to 5%, the cell membrane permeability increased acutely, but the leaf relative water content, total chlorophyll content, all photosynthesis parameters, and root activity had a significant decrease. The water use efficiency reached the peak when the soil relative moisture content was 10%. To sum up, the optimal soil relative moisture content for E. oxycarpa seedlings should be 40%-50%, and the permanent wilting coefficient of the seedlings was 4.3% (soil relative moisture content).

Key words: natural drought, Elaeagnus oxycarpa, root activity, photosynthetic characteristics, net ecosystem CO₂ exchange, meadow wetland, moisture, Horqin, temperature