The Coding of Object Thickness in Plants: When Roots Matter

Tendrils are clasping structures used by climbing plants to anchor and support their vines that coil around suitable hosts to achieve the greatest exposure to sunlight. Although recent evidence suggeststhat climbing plants are able to sense the presence of a potential stimulus in the environment and to planthe tendrils’ movements depending on properties such as its thickness, the mechanisms underlyingthickness sensing in climbing plants have yet to be uncovered. The current research set out to use threedimensionalkinematical analysis to investigate if and in what way the root system contributed to thicknesssensing. Experiment 1 was designed to confirm that the movement of the tendrils of pea plants(Pisum sativum L.) is planned and controlled on the basis of stimulus thickness when the stimulus isinserted into the substrate. Experiment 2 was designed to investigate what happens when the stimulus islifted to the ground so as to impede the root system from sensing it. The results confirmed that tendrils’kinematics depend on thickness when the stimulus is available to the root system but not when it isunavailable to it. These findings suggest that the root system plays a pivotal role in sensing the presenceand the thickness of a stimulus and that the information perceived affects the planning and the executionof the climbing plants’ reach-to-grasp movements