“…It was reported that, when soil moisture decreased, roots developed well especially in deeper soil, not only in the wheat (Box et al, 1989;Morita and Okuda, 1994;Proffitt et al, 1985) but also in soybean (Hida et al, 1995;Hirasawa et al, 1994Hirasawa et al, , 1998, cowpea, rice (Angus et al, 1983), peanut, millet (Inanaga et al, 1996), and other plants. Wheat roots in the shallower soil in the present experiment were not so long, as in earlier studies by others (Box et al, 1989;Box and Ramseur, 1993;Proffitt et al, 1985), perhaps due to the dry and compacted surface of the soil, light leakage and temperature effects, which resulted from insertion of the minirhizotron tubes (Wiesler and Horst, 1994;Smit et al, 2000). The resistance to water transport in plants in the D-plot, with their better-developed root systems, was smaller than that in the W-plot ( Table 3), indicating that plants in the D-plot had a greater capacity for water absorption (Hirasawa and Ishihara, 1991;Hirasawa et al, 1992a, b).…”