Growth Response of a Chrysanthemum Crop to the Environment. I. Experimental Techniques

The construction and mode of operation of six daylit assimilationchambers and the methods used to measure canopy photosynthesisand radiation interception are described. The chambers havea cuboid plant space, with sides 1.2 m long, in which temperaturecan be controlled from ambient to 30 °C with a temporalvariation of ±0.5 °C. Conductimetric controllersmaintain CO₂ concentration in the chambers within ±5per cent of the desired values. The amount of CO₂ injected andother variables needed to relate mean CO₂ assimilation ratesto mean radiation flux density over successive 10 min intervalsthroughout the day are recorded on punched tape for subsequentcomputer processing. The chambers have limitations in the number,range and variability of the environmental factors controlledbut they cost approximately one tenth as much as commercialdaylit cabinets and provide adequate, reproducible data formodelling many aspects of crop growth.