Figure 7.

Inhibition of auxin or gibberellins, but not brassinosteroids, represses supplemental FR light‐induced elongation in Geranium pyrenaicum. Cotyledon petiole length of G. pyrenaicum seedlings after five (a) or four (b–c) days in control white light (WL; R:FR 1.8) or WL supplemented with far‐red light (WL + FR; R:FR 0.2), combined with different concentrations of hormone inhibitors: (a) α‐(phenylethyl‐2‐one)‐IAA (PEO‐IAA; inhibitor of auxin perception), 1‐N‐naphthylphthalamic acid (NPA; inhibitor of auxin transport), (b) brassinazole (BRZ; inhibitor of brassinosteroid synthesis), or (c) paclobutrazol (PAC; inhibitor of gibberellin synthesis). Chemicals were added to a medium, to which plants were transferred 24 hr prior to the start of the light treatments. Data represent means ±SEM, n = 6–10. Asterisks mark significant differences compared to mock in the same light treatment (Student's t test, p < 0.05)