Gravitropism A. Stimulus - gravity, hence the name gravitropism. Answer - a clinostat. This device is essentially a phonograph turntable to which a plant is attached. The entire unit is held horizontally and the plant rotated to counteract the effect of gravity. The threshold intensity - the minimum amount of stimulus required to induce the response.
Roots are more sensitive than shoots.
Oat coleoptiles on in clinostat experiments respond to 0.0014 g, whereas roots require just 0.00014 g. The threshold dose - represents the minimum dose of stimulus required to induce a response, equals the product of stimulus intensity times the duration of the stimulus. The threshold dosage for oat coleoptiles varies from 30-240 g s. Usually there is a lag of about 10 minutes between the time of the dose and the response. Plant on side place upright bends.