For experiment A, approximately 5–6 discs (diameter = 2 cm)
were cut out along the midrib of 20th to 26th main leaves with a
cork borer. In square plastic Petri dishes (12 cm 12 cm; Greiner
Bio One, Solingen, Germany), 20 leaf discs were placed upside
down on three layer of filter paper (Filter MN 615; Macherey-Nagel
GmbH & Co. KG, Düren, Germany), wetted with 10 ml sterilized
demineralized water to guarantee water vapour saturation within