Responses of respiration in the light to warming in field‐grown trees: a comparison of the thermal sensitivity of the Kok and Laisk methods

Summary The Kok and Laisk techniques can both be used to estimate light respiration R light . We investigated whether responses of R light to short‐ and long‐term changes in leaf temperature depend on the technique used to estimate R light . We grew Eucalyptus tereticornis in whole‐tree chambers under ambient temperature (AT) or AT + 3°C (elevated temperature, ET). We assessed dark respiration R dark and light respiration with the Kok ( R Kok ) and Laisk ( R Laisk ) methods at four temperatures to determine the degree of light suppression of respiration using both methods in AT and ET trees. The ET treatment had little impact on R dark , R Kok or R Laisk . Although the thermal sensitivities of R Kok or R Laisk were similar, R Kok was higher than R Laisk . We found negative values of R Laisk at the lowest measurement temperatures, indicating positive net CO 2 uptake, which we propose may be related to phosphoenolpyruvate carboxylase activity. Light suppression of R dark decreased with increasing leaf temperature, but the degree of suppression depended on the method used. The Kok and Laisk methods do not generate the same estimates of R light or light suppression of R dark between 20 and 35°C. Negative rates of R Laisk imply that this method may become less reliable at low temperatures.