Respiration as measured by scanning calorimetry reflects the temperature dependence of different soybean cultivars

Soybean [Glycine max (L.) Merr.] is grown in many countries and climates. T wenty-two North American soybean cultivars from six different maturity grou ps were grown from seed under the same conditions. Measurement of metabolic heat rate of leaf tissue with a scanning calorimeter revealed that the slo pe of heat rate versus temperature when plotted on Arrhenius axes showed ab rupt changes reflecting changes in metabolism. The chilling response temper ature for all cultivars was near 17.5 degrees C, The maximum tolerable temp erature for all cultivars was near 43.5 degrees C, Differences in response to temperatures between the extremes relate to maturity group, follow latit udinal trends, and represent adaptation to different climates. Smaller diff erences were also observed between cultivars in the same maturity group. Se lection of cultivars of soybean for best growth in different climates has r esulted in relatively rapid adaptation to local temperatures. (C) 2000 Else vier Science B.V. All rights reserved.