A seedling emergence model based on thermal dependence of enzyme activity in germinating cotton was developed. The model was validated under both laboratory and field conditions with several cotton lines under diverse temperature regimes. Four commercial lines were planted on four dates in Lubbock TX in order to provide different thermal environments for germination. Differences were observed in time required for germination with some lines exhibiting enhanced germination rates. Analysis of antioxidant enzymes indicated differences in antioxidant activity and oxidative stress among lines. The emergence times predicted by the mechanistic model were comparable to those derived from a commonly used empirically derived model.