Mechanical measurement of gravitropic bending force in pea sprouts.

Environmental stimuli such as gravity and light modify the plant development to optimize overall architecture. Many physiological and molecular biological studies of gravitropism and phototropism have been carried out. However, sufficient analysis has not been performed from a mechanical point of view. If the biological and mechanical characteristics of gravitropism and phototropism can be accurately grasped, then controlling the environmental conditions would be helpful to control the growth of plants into a specific shape. In this study, to clarify the mechanical characteristics of gravitropism, we examined the transverse bending moment occurring in cantilevered pea (Pisum sativum) sprouts in response to gravistimulation. The force of the pea sprouts lifting themselves during gravitropism was measured using an electronic balance. The gravitropic bending force of the pea sprouts was in the order of 100 Nmm in the conditions set for this study, although there were wide variations due to individual differences.