Fig. 1
Overview of pea plants growing in the presented axenic hydroponic system. a Plants in the boxes were placed in a growth chamber with a 120–150 μmol m−2 s−1 light, 23/18 °C day/night temperatures and a 12/12 h day/night cycle photoperiod. The liquid medium was continuously aerated (with a flux of approximately 125 ml min−1) by fitting six individual boxes to a 3.7 W Elite 802® air pump (Rolf C. Hagen Inc., Montreal, Canada). b Detailed view of the plants growing axenically in magenta boxes filled with continuously aerated nutrient solution. The bottoms of the boxes were covered with black plastic to reduce the exposure of the roots to light. An autoclavable silicone rubber tube was introduced through a hole drilled in the lid of the vessel to bubble air into the nutrient solution. Hydrophobic cotton held the tube in the hole and avoided overpressure provoked by the incoming air. The lid was sealed with Leukopor® non-woven tape. c Autoclavable plastic mesh that holds the seeds to avoid submergence and maintains them in contact with the nutrient solution. d Air splitter control valve that regulates the pressure of the air bubbling the nutrient solution. e Autoclavable silicone rubber tube connected to a 200 µL pipette tip at the end of the tube to bubble the nutrient solution. A 0.22 µm Millex® vent filter is connected to the top of the tube for the sterilisation of the incoming air