Transcriptional analyses of ZmDUR3 in root and shoots of maize in response to urea treatment. 5 day-old plants were exposed for a maximum of 4 hours to nutrient solution without addition of any N source (Control plants) or supplied with 1 mM urea (Urea treated plants). Gene mRNA levels were normalized with respect to the mean transcript level of the housekeeping gene ZmRPS4; relative changes in gene transcript levels were calculated on the basis of the mean transcript level of ZmRPS4 in roots of Control plants at 0 hour (Relative gene expression = 1). Values are means ± SD of three independent experiments (ANOVA, Student-Newman-Keuls, P < 0.05, n = 3). Capital letters are referred to the statistical differences in the roots, while lower letters are referred to shoots.