generally show greater differences (Box and Ramseur, 1993). Several methods have been used to estimate root Image analysis has greatly simplified the measurement of root length (Rowse and Phillips, 1974;Richards et al., 1979; systems, allowing more detailed and accurate assessment of standard Zoon and Van Tienderen, 1990). The most widely emroot variables. However, maize (Zea mays L.) root morphology has primarily been studied in conventional hybrids. We tested the hypoth-ployed methods are based on the line intersect principle, esis that genotypes carrying the leafy trait (taller plants with more which was first devised by Newman (1966) and later leaves and greater leaf area development) would have root morpholomodified (Marsh, 1971; Tennant, 1975). Because this gies differing from those of conventional maize hybrids. A 3 ϫ 3 method relies on visual counting of grid line-root interfactorial experiment was arranged in a randomized complete block cepts, it can be time consuming and prone to inaccuracy, design with three blocks, three fertilization levels (0, 127.5, and 255 especially when measuring samples with a large proporkg N ha Ϫ1 as NH 4 NO 3 ), and three maize genotypes [leafy reduced tion of fine roots (Smit et al., 1994). However, the line stature (LRS), leafy normal stature (LNS), and a conventional comintercept method improved root measurement and, in mercial hybrid Pioneer 3905 (P3905)]. The genotypes were selected particular, reduced the time required for analysis comfor their contrasting canopy and root architectures. Plants were grown pared with simpler, manual methods. For example, the in 63-L plastic containers, and the roots were measured at the silking stage (80 d from emergence) by scanner-based image analysis. In