Fig. 12. Effects of increasing CO2 concentrations corresponding to increasing soil water contents in the root zone on the tuberous root development in Experiment 1 and
2. Relative values of tuberous root dry weights compared with the maximum value, 283.2 g, obtained in soil ridges irrigated every three days in Experiment 1 were plotted
as an index of the tuberous root development. Soil CO2 concentrations in Experiment 1 were estimated from the relationship between CO2 concentrations and volumetric
water contents obtained in the supplementary experiment.