When plant tissue is wounded a number of protective processes start. We have made a study by isothermal calorimetry of the heat production response of root and tuber tissue to wounding. Samples with different surface to volume ratios were prepared from carrots, potatoes and swedes (rutabaga) and the thermal power was measured in closed glass ampoules in a TAM Air isothermal calorimeter. The evaluation was made by assuming that a certain heat production rate per volume tissue was associated with the normal metabolic activity, and that another heat production rate per surface area was associated with the wound response. The results showed that the wound response part was high; in some cases almost half the heat came from the wound response and not from the ordinary metabolic activity. We also discuss and give some evidence that the effect seen is not caused by limited supply of oxygen to the core of our samples. This is an important factor to take into account when making calorimetry on cut biological samples. It also shows that isothermal calorimetry can be used for the study of wound response in vegetable tissue. (C) 2004 Elsevier B.V. All rights reserved.