Temporal course of graviperception in intermittently stimulated cress roots |
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Authors: | Hejnowicz Z Sondag C Alt W Sievers A |
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Institution: | Botanisches Institut, Universität Bonn, Venusbergweg 22, D-53115 Bonn, Germany |
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Abstract: | Gravitropic bending of Lepidium roots caused by intermittent stimulation lasting ≈ 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 ≈ 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. |
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Keywords: | Lepidium sativum L Brassicaceae cytoskeleton gravitropism intermittent stimulation root stimulation threshold |
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