A respiration based description of plant growth rate responses to temperature

The temperature dependence of metabolic rates determines how plant growth rates vary with temperature. This paper shows that equations on physiological relations between respiration rates (i.e. rates of heat loss and CO2 evolution) and growth rates can be used to describe temperature effects on plant growth rate. Incorporating measured values of plant respiratory heat and CO2 rates at a few temperatures into the equations allows description of growth rates as a function of temperature and provides a physiological basis for understanding the effects of temperature on growth rate. The paper presents data on cabbage (Brassica oleracea L. Capitata) and tomato (Lycopersicon esculentum Miller cv. Ace) as model cool-climate and warm-climate cultivars to illustrate application of the methods in determining optimal growth climates for different cultivars, accessions, and ecotypes. The respiration-based calculations of growth rate vs. temperature yield curves for both species that are consistent with known temperature-growth requirements. We conclude that plant responses to temperature can be accurately predicted in detail from respiration rate measurements and the growth-respiration model. These studies demonstrate that the temperature dependence of growth rates is a function of the temperature dependencies of both metabolic rates and metabolic efficiency, which change continuously with temperature. The ultimate cause of high- and low-temperature growth limits is commonly not membrane phase transitions or enzyme denaturation as has been supposed, but is loss of substrate carbon conversion efficiency. The results show that ''plant temperature stress'' has been misunderstood and must be redefined because there is no ''nonstressfull temperature''.