Effects of homogeneous low nitrate or local high nitrate supplies on lateral root development of four maize root types. Seedlings or adult plants were grown in homogeneous low nitrate nutrient solution before each root type was transferred to local high nitrate nutrient solution (see “Materials and Methods”). Roots were scanned and counted after 20 d of growth in these two nitrate conditions. A and B, Average lateral root length (A) and lateral root density (B) in the lateral root branching zone under homogenous low nitrate and local high nitrate conditions. Error bars indicate means ± se; n = 4 (roots from four different maize plants). C to F, Early pericycle cell divisions in primary (C), seminal (D), crown roots (E), and brace roots (F) 24 h after local high nitrate supply. F is taken from Yu et al. (2015a) as a reference for comparisons with the other root types. Asymmetric pericycle cell divisions were tracked from 5 to 80 mm from root tip after Safranin O and Fast Green staining. Error bars indicate means ± se; n = 4 (roots from four different) maize plants. Asterisks denote significant differences according to paired Student’s t tests (*P < 0.05; **P < 0.01). PR, primary root; SR, seminal root; CR, crown root; BR, brace root. F was adapted from Yu et al. (2015a).