Experimental results: The experiments of Frits Went
Following up on the work of Boysen-Jensen, Frits Went placed the decapitated tips of dark-grown oat coleoptiles on tiny agar blocks, permitting the chemical signal that controlled elongation in the dark and bending in the light to diffuse into the agar. He then placed these agar blocks on top of decapitated, dark-grown coleoptiles. Agar blocks that had been exposed to a coleoptile tip (pink) caused the coleoptile to elongate. Control blocks that had not been exposed to a coleoptile tip (white) did not cause the coleoptile to elongate.
As shown in the labels below, Went extended his experiments by placing the control (white) and treated (pink) agar blocks off-center on top of decapitated coleoptiles. Some he left in the dark (indicated by the gray background), and some he exposed to directional light (indicated by the yellow arrows).
Sort the following coleoptiles into the appropriate bins depending on if they will bend to the left, bend to the right, or not bend at all.