Relative expression of the ethylene perception genes, ERS1, ERS2 and ETR2 in young and mature leaves of the wild type and vte1 and vte4 mutants of A. thaliana plants exposed to control, salt stress or water stress conditions for 7 d. Data are the mean ± SE of n = 4 experiments. Significant differences between genotypes, leaf type and their interaction (genotype × leaf type) are given in the panels (ANOVA, P ≤ 0.05). NS, not significant. GAPDH was used as the reference gene to calculate relative expression of the ethylene perception genes.