Fig. 2. 24-hour total of respiration (R) plotted against 24-hour total of photosynthesis (P), for various sizes of plant, in increasing order of weight from the bottom of the chart. The 4 plants were given constant light throughout the 12-hour day, but a different level of light each day, in the order 100, 40, 20, 5, 20, 40, 100W m^-2.