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Gravitropic responses of the Avena coleoptile in space and on clinostats. I. Gravitropic response thresholds
Author(s) -
Brown Allan H.,
Chapman David K.,
Johnsson Anders,
Heathcote David
Publication year - 1995
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/j.1399-3054.1995.tb00803.x
Subject(s) - clinostat , coleoptile , weightlessness , gravitropism , avena , chemistry , biophysics , stimulus (psychology) , biological system , physics , botany , biology , biochemistry , psychology , astronomy , arabidopsis , gene , mutant , psychotherapist
We conducted a series of gravitropic experiments on Avena coleoptiles in the weightlessness environment of Spacelab. The purpose was to test the threshold stimulus, reciprocity rule and autotropic reactions to a range of g‐force stimulations of different intensities and durations The tests avoided the potentially complicating effects of earth's gravity and the interference from clinostat ambiguities. Using slow‐speed centrifuges, coleoptiles received transversal accelerations in the hypogravity range between 0.1 and 1.0 g over periods that ranged from 2 to 130 min. All responses that occurred in weightlessness were compared to clinostal experiments on earth using the same apparatus. Characteristic gravitropistic response patterns of Avena were not substantially different from those observed in ground‐based experiments. Gravitropic presentation times were extrapolated. The threshold at 1.0 g was less than 1 min (shortest stimulation time 2 min), in agreement with values obtained on the ground. The least stimulus tested, 0.1 g for 130 min, produced a significant response. Therefore the absolute threshold for a gravitropic response is less than 0.1 g.