PMC

The changes in SMC and PR in shallow and hardpan layers under different water treatments in Exp. 1 (a) and under different water and hardpan bulk density (BD) treatments in Exp. 2 (b). Horizontal bars along x-axis in Fig. 1a,b indicate the prevailing soil moisture conditions during SMF. The relationships between the changes in SMC and PR in shallow and hardpan layers in Exp. 1 and 2, respectively (c,d). The BD of the shallow layer was 1.25 g cm⁻³ in both Exp. 1 and 2 while that of the hardpan layer was 1.50 g cm⁻³ in Exp. 1 and either 1.50 or 1.70 g cm⁻³ in Exp. 2. WW, well-watered and SMF, soil moisture fluctuation treatments. Error bars represent the standard deviation calculated from 3 replicates. ***Indicate significant at P < 0.001.

The total root length (a,d), total lateral root length (b,e) and total nodal root length (c,f) below the hardpan layer in IR64 and its INL, YTH304, under different water treatments in Exp. 1 (a–c) and under different water and hardpan BD treatments in Exp. 2 (d–f). The bulk density of the shallow soil layer was 1.25 g cm⁻³ while that of the hardpan layer was 1.50 g cm⁻³ in Exp. 1 and either 1.50 or 1.70 g cm⁻³ in Exp. 2. WW, well-watered and SMF, soil moisture fluctuation treatments. Error bars represent the standard deviations calculated from 3 replicates. *Indicates significant difference between the two genotypes at P < 0.05, by Student’s t-test.

The plasticity in nodal root elongation through the hardpan at different soil moisture conditions during SMF treatment in IR64 and introgression line YTH304 in Exp. 1 (a) and Exp. 2 (b). The bulk density of the hardpan layer was 1.50 g cm⁻³ in Exp. 1 and either 1.50 (red and blue symbols) or 1.70 g cm⁻³ (violet and yellow green symbols) in Exp. 2. Horizontal bars along x-axis indicate the prevailing soil moisture conditions during SMF. Error bars represent the standard deviation calculated from 3 replicates.

Total water use (a,c) and shoot dry weight (b,d) of IR64 and its INL, YTH304, under different water treatments in Exp. 1 (a,b) and under different water and hardpan bulk density (BD) treatments in Exp. 2 (c,d). The BD of the shallow soil layer was 1.25 g cm⁻³ while that of the hardpan layer was 1.50 g cm⁻³ in Exp. 1 and either 1.50 or 1.70 g cm⁻³ in Exp. 2. WW, well-watered and SMF, soil moisture fluctuation treatments. Error bars represent the standard deviation calculated from 3 replicates. Asterisk (*) indicates significant difference between the two genotypes at P < 0.05, by Student’s t-test.