Experimental separation of sensory and motor functions in pea tendrils.

When illuminated pea tendrils from light-grown plants are rubbed on their abaxial side, they rapidly coil in a spiral fashion. If similar tendrils are held in the dark for 3 days and then rubbed, however, they will not coil until they are subsequently illuminated. They can remain uncoiled in the dark for as long as 2 hours after stimulation, and will still coil immediately when they are illuminated. Tendrils that are rubbed and held at 25 degrees C will coil, but those treated at 5 degrees or 10 degrees C will not. However, tendrils rubbed at 25 degrees C and kept from coiling for an hour at 5 degrees C, will immediately coil when restored to the higher temperature. These observations are interpreted to imply separation of sensory and motor functions.