A dynamic model of cotton emergence based on the thermal dependence of malate synthase
Cotton (Gossypium hirsutum L.) is frequently planted when temperatures are not optimal for germination and emergence. Delayed emergence, a common contributor to diminished plant performance later in the season, is often related to nonoptimal temperatures. Improvement of cotton performance requires knowledge of the source, pattern, and magnitude of thermal limitations on seedling metabolism. In this study the thermal dependence of malate synthase, an enzyme involved in cotton seedling lipid metabolism, was used to define the pattern and magnitude of thermal limitations and as the basis of a metabolic model to predict emergence under variable temperatures in the field. Soil temperature at seed depth was monitored over the cotton-planting season of 2005 and characterized as optimal, suboptimal, and supraoptimal. Suboptimal temperatures were common and supraoptimal temperatures were less frequent. A metabolic model to predict emergence was developed and the predicted emergence was in agreement with a widely used degree-day based model. Metabolic indicators of thermal optimality may prove useful in studies of seedling responses to thermal variation.