Effect of Night Temperature on Photosynthesis, Transpiration, and Growth of Spray Carnations

Spray carnation plants were grown for several weeks under an 8 h day/16 h night regime at temperatures of approximately 21 °C by day and 6, 17, or 30 °C by night. Subsequently, the rates of photosynthesis and transpiration at 20 °C were similar. This contrasts with evidence published for some other species. Night temperature had only a slight effect on the plant's growth rate. Leaf area ratios were also similar between treatments and for two intervals covering a 5 week period. At the high night temperature flowers were initiated sooner and there were fewer side shoots per plant than at the lower temperatures. The implications of these results for the optimization of the climatic environment are discussed briefly, and the results are compared with those reported for other species.