Abstract: To assess the combined effects of soil moisture, light, and other environmental factors on the stomatal conductance of cassava (Manihot esculenta Crantz), and to construct the mathematical models of stomatal conductance and related environmental factors, a gradient of soil moisture content at an interval of 10% within the range of 20%-80% was installed for the cassava cultivar SC-8 in a pot culture experiment, with the net photosynthetic rate, stomatal conductance, air humidity, and several other parameters measured. There was a significant positive correlation between air humidity and stomatal conductance. Photosynthetically active radiation and soil moisture content had significant positive correlations with stomatal conductance, but their affecting magnitude varied with soil moisture content. When the soil moisture content was low, it was the dominant factor affecting stomatal conductance; when the soil moisture content was high, photosynthetically active radiation became the dominant affecting factor. The relationships of stomatal conductance with soil moisture content, photosynthetically active radiation, and air humidity could be expressed with exponential model. Using the constructed model, we found that the lowest threshold of appropriate soil moisture content for cassava cultivar SC-8 was 52%.

Key words: Hemicentrotus pulcherrimus, Selectivity, Tolerance, Experimental ecology