Glycine max cultivars exhibit differential tolerance to soil-applied sulfentrazone. The intent of this study was to determine the physiological basis for this differential tolerance by evaluating sulfentrazone absorption and metabolism during the earliest stages of G. max development (i.e., germinating seeds, and germinal seedlings). Imbibed seeds (24 h) of the sulfentrazone-tolerant cultivar ‘Stonewall’ absorbed 37% less sulfentrazone than the sulfentrazone-sensitive cultivar ‘Asgrow 6785’. Similarly, germinal seedlings (i.e., 60 h from start of imbibition) of the sulfentrazone-tolerant cultivars Stonewall and ‘Pioneer 9593’ absorbed 22% less sulfentrazone than the sulfentrazone-sensitive cultivars Asgrow 6785 and ‘Carver’ when exposed to sulfentrazone-containing solution for either 24 or 48 h. The amount of root-absorbed 14C-sulfentrazone that was translocated into cotyledon or hypocotyl tissues did not exceed 11% of the amount absorbed and was similar for all four cultivars. Sulfentrazone metabolism by both imbibed seeds and by germinal seedlings was independent of cultivar. Increasing the sulfentrazone concentration in the seed imbibition solution and increasing the temperature resulted in greater seedling height reduction at 10 d in Asgrow 6758 than in Stonewall. Results indicate that differential absorption during the earliest stages of development is the basis for the differential response among G. max cultivars. Comparatively limited sulfentrazone absorption by Stonewall, as reflected in acceptable seedling injury, remained relatively consistent across the range of concentrations and temperatures evaluated.
Nomenclature: Sulfentrazone; Glycine max (L.) Merr., soybean.