Submitted to: American Society of Plant Physiologists Meeting
Publication Type: Proceedings
Publication Acceptance Date: 7/29/1996
Publication Date: N/A
Technical Abstract: Thermal variation is common within the upper regions of the soil during seed germination and seedling growth. Management decisions at and following planting can alter the thermal environment of the seedling and its subsequent growth and development. The thermal dependence of the activity of malate synthase, an enzyme involved in seedling lipid metabolism, was determined in the laboratory and an optimum thermal range defined (26-39 C). The thermal dependence of the development of malate synthase activity following germination was used in conjunction with the thermal dependence of reaction rate to develop a model of malate synthase activity as a function of temperature. The soil temperature at a soil depth of 5cm was monitored for 50 days in the late spring of 1994 to define the thermal environment for a variety of potential planting dates. Two row spacings; 30 and 40 inches and two irrigation regimes; dry (single preplant irrigation) and irrigated (preplant and 14-day irrigations) were established. The thermal dependence of the malate synthase activity was modeled using the soil temperatures to produce computer visualizations of enzyme activity for various planting dates and management treatments. Both high and low temperature limitations on malate synthase activity were identified and quantified. The irrigated-40-inch treatment was subjected to the least thermal stress while the dry-30-inch treatment experienced the highest thermal stress.