Time-temperature responses of tomato cells during high- and low-temperature inactivation

Precise time and temperature dependences of the decrease of metabolism of cultured cells of tomato (Lysopersicon esculentum (L.) Mill. L. peruvianum (L.) Mill.) resulting from exposures to high and low temperatures were determined. Equations of the form Ln (activity)= C +1 A+(T-T_m)^N+B] describe thermal inactivation and allow prediction of activity loss following any thermal excursion beyond limits of temperature stability. The experimental parameters A, B, C and N derived from these equations allow precise comparison of temperature sensitivities of cells. Analysis of metabolic heat rates, O₂-consumption rates and CO₂-evolution rates demonstrated simultaneous shifts in metabolic pathways and metabolic activities towards more anaerobic metabolism below about 12° C and at high temperatures that stress growth of tomato cells.We gratefully acknowledge support for this project by the U.S. Department of Agriculture Competitive Research Grants Office, grant 90-37280-5592. Allied support by Pioneer HiBred Inc., the California Rice Research Board, and Dole Package Foods Co., Division of Castle and Cooke Co., has also been helpful to this work.