Root morphology of contrasting maize genotypes

Image analysis has greatly simplified the measurement of root systems, allowing more detailed and accurate assessment of standard root variables. However, maize (Zea mays L.) root morphology has primarily been studied in conventional hybrids. We tested the hypothesis that genotypes carrying the leafy trait (taller plants with more leaves and greater leaf area development) would have root morphologies differing from those of conventional maize hybrids. A 3 X 3 factorial experiment was arranged in a randomized complete block design with three blocks, three fertilization levels (0, 127.5, and 255 kg N ha(-1) as NH4NO3), and three maize genotypes [leafy reduced stature (LRS), leafy normal stature (LNS), and a conventional commercial hybrid Pioneer 3905 (P3905)]. The genotypes were selected for their contrasting canopy and root architectures. Plants were grown in 63-L plastic containers, and the roots were measured at the silking stage (80 d from emergence) by scanner-based image analysis. In general, greater root length and root surface areas were obtained at an N fertilization rate of 127.5 kg N ha(-1) compared with either the absence of fertilizer N or the higher rate of 255 kg N ha(-1). For all genotypes 95% of root length was comprised of roots ranging from 0.20 to 0.40 rum in diameter. Total root length (4 kin) and total root surface area (3.2 m(2)) were similar for LNS and LRS genotypes and were greater than those of P3905 (1.4 km total root length and 1.1 m(2) surface area). Root diameter did not differ among genotypes.