During the growing cycle, the night temperature inside the
greenhouse ranged from 17.2 to 21.5 ◦C (heating set point: 18 ◦C)
while the day temperature was between 23.7 and 34.9 ◦C. Relative
humidity was kept around 70% and the CO2 concentration near
500 ppm. Supplemental lighting by High Pressure Sodium lamps
(Philips SON-T Green Power 600W; Koninklijke Philips Electronics
N.V., the Netherlands) provided a minimum photon flux density of
150Wm−2 at the crop level, extending the natural day-length to
16 h (3:00 till 19:00). Lamps switched off when the outside global
radiation exceeded a 250Wm−2 threshold.