Fig. 2. Net photosynthesis (daytime carbon exchange), night respiration (night respiration), and carbon use efficiency [(daily carbon gain)/(gross photosynthesis)] for lettuce (A and D), tomato (B and E), and soybean (C and F). Data points are the average of two chambers for a given temperature. Carbon exchange rates are per m² of ground area. Temperature treatments were initiated on day 17 for lettuce and tomato, and day 18 for soybean.