Figure 4.

Δ6-12 oat phyA is active in the VLFR but reduces the HIR of hypocotyl growth in etiolated Arabidopsis. A, One-day-old seedlings of the WT, or expressing either FL or Δ6-12 oat phyA, were exposed for 3 d to continuous FR (5 and 50 μmol m⁻² s⁻¹) or hourly pulses of FR (3 min, 100 μmol m⁻² s⁻¹). Two FL and Δ6-12 transgenic lines are included. In each case, the left bar is a strong expression line (see Fig. 2A) and the right bar shows a weak expression line (3% oat phyA compared with strong expression lines). B, Seedlings of independent transgenic lines expressing different levels of FL or NF oat phyA (it includes the lines shown in Fig. 2D plus additional lines) were exposed to hourly or continuous FR. The VLFR was calculated as the difference between hypocotyl length in darkness (1.00) and under hourly FR. The HIR for 5 (dotted lines) and 50 (solid lines) μmol m⁻² s⁻¹ were calculated as the difference between hourly and continuous FR. C, Four-day-old seedlings were exposed for 8 h to either hourly or continuous FR and hypocotyl length was measured 24 h later (at the beginning of the FR treatments hypocotyl length was approximately 86% of the length of dark controls 24 h later). Data are means and se of five (A and B) or 12 (C) replicates boxes.