All experiments were carried out with 2-d-old seedlings of
Z. mays ‘Limko’. Maize caryopses were soaked in running
tap water for 5 h. Next they were placed in Petri dishes and
stacked between layers of wet paper. The Petri dishes were
placed vertically in a dark chamber at 29 8C and high
humidity. After 48 h, seedlings with straight main roots
about 10–15 mm long were used for the experiment.