Temporal course of graviperception in intermittently stimulated cress roots.
Gravitropic bending of Lepidium roots caused by intermittent stimulation lasting approximately 1 h was the same for a particular sum of stimulation intervals and was independent of (i) the length of a single stimulation interval (from 1 to 12.2 s) during which the roots were exposed unilaterally and horizontally, and (ii) rest intervals (from 60 to 300 s) during which roots were horizontally rotated at two revolutions per minute on a clinostat. The same effectiveness of equal sums of short stimulations separated by relatively long rest intervals indicates that the signals into which the stimuli are transduced are: (i) additive; (ii) proportional to the duration of a single stimulation; and (iii) stable for at least 5 min. The perception time is shorter than 1 s, the presentation time is approximately 10 s. The effects of intermittent stimulation fit the hypothesis that the gravity-induced movement of statoliths changes asymmetrically the stress in cytoskeletal actin filaments, thereby inducing gravitropic bending.
Hejnowicz
Z
Z
Botanishches Institut, Universitat Bonn, Germany.
Sondag
C
C
Alt
W
W
Sievers
A
A
D019607:Brassicaceae / Q000166:cytology / Q000254:growth & development / Q000502:physiology*; D003599:Cytoskeleton / Q000502:physiology; D006112:Gravitation; D018522:Gravitropism; D018466:Gravity Sensing / Q000502:physiology*; D018517:Plant Roots / Q000166:cytology / Q000254:growth & development / Q000502:physiology*; D012399:Rotation; D012639:Seeds; D013997:Time Factors