The Darwin and Boysen-Jensen Phototropism Experiments, Worked
This video presents the same text shown beside it, spoken and on screen. It adds nothing the text does not say.
State
This procedure traces how two classic experiments located phototropism's signal at the shoot tip and identified it as a diffusible chemical rather than a direct light response along the stem.
Watch for
A single experiment alone cannot separate "detection happens at the tip" from "the tip alone can bend" — it takes the mica-barrier control specifically to show the signal must be a diffusible chemical rather than a structural or electrical connection.