© 1994 Heron Publishing—Victoria, Canada
A whole-plant cuvette system to measure short-term responses of conifer seedlings to environmental change
N. J. Livingston, G. J. Davies, B. M. Eby, G. Filek, E. E. Fuchs, S. Pepin and R. E. Percy
Department of Biology, University of Victoria, Victoria, B.C. V8W 2Y2, Canada / Received July 12, 1993
Summary
A computer-controlled whole-plant cuvette system is described that allows precise and independent control of temperature (±
0.05 °C), vapor pressure (± 0.02 kPa), CO2 concentration (± 2 µmol mol–1) and photosynthetic photon flux density (± 5 µmol m–2 s–1), and allows the continuous measurement of net photosynthesis and transpiration rates. Vapor pressure is controlled by circulating
chamber air through a CaSO4 desiccant column supported on a digital balance. Transpiration rate is calculated from the change in desiccant mass with
time. Photosynthesis rate is measured by integrating the output of a mass flow controller used to inject CO2 into the chamber to compensate for that assimilated by the plant.
The control system can be driven by set points that can be varied, for example, as a function of time, or held constant. We
were able to simulate weather data obtained from climate stations and accurately follow, in real time, the output of sensors
measuring outside conditions.
Experiments on well-watered one- and two-year-old nursery-raised western red cedar (Thuja plicata Donn.) and white spruce (Picea glauca (Moench) Voss) seedlings showed that if the mean daily temperature was increased from 20 to 22 °C with vapor pressure remaining
constant at 1 kPa, CO2 concentrations must almost double to compensate for the decrease in net photosynthesis rate.
Keywords:
photosynthesis, temperature, transpiration, vapor pressure.
