Uniform-sized seedlings of lettuce at the 5-leaf stage were individually
raised in a polystyrene foam cube, then mounted into
a Styrofoam plate with eight holes, and placed in a container
(59 cm × 48 cm × 9.7 cm) filled with continuously aerated complete
nutrient solution (Gul et al., 2005) in a commercial growth chamber
(CH-202-A, CHIN-HSIN, Taipei, Taiwan).