*4.2. Light Treatments*

Within each chamber, four LED modules (Sunsim VIS\_v3; Compled Solutions GmbH, Dresden, Germany) were placed which allowed to adjust light intensity for the different wavelength ranges. The applied light treatments were comprised only of red and blue light, with one peak in the blue range at 440 nm and two peaks in the red range at 620 and 640 nm (Figure 6). The day length was set to 10 h and all treatments had a PPFD of 400 µmol m−<sup>2</sup> s −1 to test the influence of different levels of BPFD independent from changes in PPFD. The spectrum of the six light treatments had a BPFD of 60, 110, 160, 210, 260 and 310 µmol m−<sup>2</sup> s −1 (B60–B310) (Figure 6), while the remaining PPFD was delivered by the red LEDs. The light spectrum did not include any far-red light to exclude differences in phytochrome-mediated responses between the light treatments. Setting of the spectral intensity of the treatments was performed at 80 cm distance from the LED modules according to the measurements from a FLAME-S-XR1-ES spectrometer (Ocean Optics Germany GmbH, Ostfildern, Germany). The spectrometer measured in the range from 200–1025 nm with a resolution of around 2 nm and was equipped with a collimating lens (74-UV-MP) and a right-angle reflector with cosine corrector (74-90-UV-CC3). The photon flux density was recorded for 400–700 nm (PPFD), 400–500 nm (BPFD) and 600–700 nm (red light).

**Figure 6.** The measured spectrum of the six treatments with a BPFD of 60, 110, 160, 210, 260 and 310 µmol m−<sup>2</sup> s −1 .

Energy consumption of the treatments was measured with a volt-ohm meter (Voltcraft, Energy Check 3000, Conrad Electronic SE, Wernberg-Köblitz, Germany). The measurements were reasonable as compared to the estimated energy consumption given by the software of the LED chambers.
