Fig. 5. Effect of night temperature on respiration (A) and carbon use efficiency (B) in lettuce, tomato and soybean relative to the control. Soybean respiration was significantly more temperature sensitive than tomato (t = 4·05, d.f. = 8, P < 0·005), and tomato respiration is significantly more sensitive than lettuce (t = 3·418, d.f. = 8, P < 0·025). Soybean CUE was significantly more sensitive to temperature than tomato (t = 2·04, d.f. = 8, P < 0·05), and tomato CUE was marginally more sensitive to temperature than lettuce (t = 1·64, d.f. = 8, P ≈ 0·08). Data are normalized to the control temperature (25 °C in lettuce and tomato, and 20 °C in soybean).