Fig. 3.

Arabidopsis thaliana Columbia plants exposed to: air (control), submergence, 3 µl L⁻¹ ethylene (flow through at 0·4 L min⁻¹), spectral shade, low red : far-red (R : FR) light and spectral neutral shade for 6 h. Growth conditions are described in Millenaar et al. (2005). All treatments resulted in rapid hyponastic growth of the petioles. See Table 2 for numerical details. Light conditions: control, ethylene [white light: PAR = 140 µmol m⁻² s⁻¹, R : FR (655–665 nm : 725–735 nm) = 1·0], submergence treatment [PAR = 100 µmol m⁻² s⁻¹, R : FR = 1·4], spectral shade [white light filtered through one layer of Fern Green filter (Lee Filters no. 122), PAR = 70 µmol m⁻² s⁻¹, R : FR = 0·2], low R : FR [white light supplemented with far-red light (FR-emitting LEDs), PAR = 140 µmol m⁻² s⁻¹, R : FR = 0·2] and spectral neutral shade [white light filtered through neutral shade cloth, PAR = 20 µmol m⁻² s⁻¹, R : FR = 1·0].