Figure 1.

Acquisition of epidermal cell length profiles, diversity of maize lateral roots and examples of cell length profiles collected in roots of different types. (A) Autofluorescence microphotography of a maize lateral root apex obtained as a composite of 3 different microscopy images (black background). Arrowheads in the inbox indicate root hair bulges. The most rootward epidermal cell with a visible root hair bulge is indicated by a red arrowhead. (B) Zoom on a meristematic zone. (C) Epidermal cell lengths (blue points) were sampled along the longitudinal axis of the root. The positions of the root cap junction (gray line; origin of the longitudinal axis) and of the most rootward root hair bulge (red line) were recorded. Root diameter was sampled at two different positions beyond the first root hair (orange arrows). (D) Typical display of lateral roots along a maize primary root. Lateral roots were visually classified in 3 categories depending on length at a given insertion point and distance from tip to first root hair, indicative of root growth rate. Red, green, and blue refer respectively to long and vigorous roots (type A), short (<10 mm) and arrested roots (type C) and intermediate, slow growing roots (type B). (E–G) Examples of lateral root tips sampled from the three types. Types B and C had visually short distances between tip and first root hair position. (H–J) Examples of cell length profiles from lateral roots belonging to the three types shown in (E–G) respectively. Data from 4 to 7 individual roots are merged. Vertical dotted lines mark the position of the first root hair bulge visible in fluorescence images.