UV-B-induced cotyledon opening in ecotype Columbia and hy5-215. The median cotyledon opening angle for each line in each of the three separate experiments is shown. Overall P value from a general linear model for the comparison of the extent of opening in the two lines is P = 0.0116. Interactions between experiment number and line were significant. For experiment 1, Col n = 15, hy5 n = 15. For experiment 2, Col n = 10, hy5 n = 16. For experiment 3, Col n = 10 and hy5 n = 10. Pairwise permutation tests on each time point individually gave P < 0.0001.