Figure 1.

Hypoxia promotes AR elongation while ethylene acts as an inhibitor of AR initiation and growth. A: ARs were grouped into three categories based on the developmental stages described by Casimiro et al. (2003) for lateral root development. Representative ARs are shown from each category. B: AR density of 11‐day‐old wild type and mutant seedlings at normoxia. Error bars represent ± SE from three biological replicates and letters show statistically different values (one‐way anova with Tukey′s test, n = 22–26, P < 0.05). C: AR of wild type, ein3 eil1, hre2‐1 and HRE2ox1 seedlings were counted and categorised as described in (A) in three biological replicates. Values are means (±SE) with single lowercase, capital or double capital letters indicating significant differences within each category (Kruskal–Wallis test, n = 22–26, P < 0.05). D: Average AR densities (±SE) were obtained in three biological replicates. Different letters indicate significantly different values (one‐way anova with Tukey′s test, n = 26–29, P < 0.05). E: 5‐day‐old seedlings were transferred to 21% or 2% O₂ with or without 5 μl·l⁻¹ ethylene for 6 days. ARs were categorised as shown in (B). Values are means (±SE) with single lowercase, capital and double capital letters indicating significant changes within the respective developmental category (Kruskal–Wallis test, n = 26–29, P < 0.05).