The expanded temperature control kit, which contains two water jackets through which water is circulated using a submersible pump, was used to make measurements at low temperatures (10 and 15 °C). The water channels were connected to a water bath and the temperature was controlled by adding ice water. For temperatures above 25 °C, the seedling and the entire gas-exchange system were covered by a plastic tent (hand-made closed chamber using transparent plastic and wood pickets, and measuring 1 m × 1 m 1.5 m). The temperature within the plastic tent was brought to the desired temperature, i.e. between 30 and 40 °C, using a portable 1500 W ceramic heater (CZ448, Comfort Zone, Pottsville, PA, USA). This made it possible to maintain the difference between the ambient air and that within the conifer chamber below 2 °C, and to prevent water condensation in the exhaust tube or in the cuvette. In fact, because of the large volume of the conifer chambers, there is an important issue of water condensation when the temperature in the chamber is warmer than that of the entering air.