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Random root movements in weightlessnessThe dynamics of root growth was studied in weightlessness. In the absence of the gravitropic reference direction during weightlessness, root movements could be controlled by spontaneous growth processes, without any corrective growth induced by the gravitropic system. If truly random of nature, the bending behavior should follow so-called 'random walk' mathematics during weightlessness. Predictions from this hypothesis were critically tested. In a Spacelab ESA-experiment, denoted RANDOM and carried out during the IML-2 Shuttle flight in July 1994, the growth of garden cress (Lepidium sativum) roots was followed by time lapse photography at 1-h intervals. The growth pattern was recorded for about 20 h. Root growth was significantly smaller in weightlessness as compared to gravity (control) conditions. It was found that the roots performed spontaneous movements in weightlessness. The average direction of deviation of the plants consistently stayed equal to zero, despite these spontaneous movements. The average squared deviation increased linearly with time as predicted theoretically (but only for 8-10 h). Autocorrelation calculations showed that bendings of the roots, as determined from the 1-h photographs, were uncorrelated after about a 2-h interval. It is concluded that random processes play an important role in root growth. Predictions from a random walk hypothesis as to the growth dynamics could explain parts of the growth patterns recorded. This test of the hypothesis required microgravity conditions as provided for in a space experiment.
Document ID
20040089297
Acquisition Source
Kennedy Space Center
Document Type
Reprint (Version printed in journal)
Authors
Johnsson, A.
(Univ. of Trondheim Norway)
Karlsson, C.
Iversen, T. H.
Chapman, D. K.
Date Acquired
August 21, 2013
Publication Date
February 1, 1996
Publication Information
Publication: Physiologia plantarum
Volume: 96
Issue: 2
ISSN: 0031-9317
Subject Category
Life Sciences (General)
Distribution Limits
Public
Copyright
Other
Keywords
STS-65 Shuttle Project
manned
Flight Experiment
NASA Center KSC
short duration
NASA Discipline Plant Biology

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