Plasmodium of P. polycephalum was cultivated in plastic containers,
on paper towels sprinkled with distilled water and fed with oat
flakes (Alnatura Haferflocken, Feinblatt, Germany). The experimental
substrate was 2% non-nutrient agar gel (Agar-Agar, Kobe I,
pulverized. Carl Roth, Germany) poured in 9 cm plastic Petri
dishes. In each experiment an oat flake colonized by a plasmodium
was placed in the center of the Petri dish. Protoplasmic tubes were
mechanically stimulated with a human hair approximately 50 mm
in diameter, 4–5 cm in length. During actuation of a protoplasmic
tube fragment, a tip of hair was forced into a wall of the tube until
temporary invagination of the wall and/or immediate stoppage of
cytoplasmic flow occurred. Videos of cytoplasmic flows were
recorded using digital high-resolution microscope Keyence VHZ20R
(KEYENCE Microscope Europe) at zoom 200